----

----

|   | x | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |
|--------|---|------------------------------------------------------------------------------------------------|

|   | For the fiscal year ended December 31, 2010 |
|--------|--------------------------------------------------|

|   | Or |
|--------|----|

|   | o | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |
|--------|---|----------------------------------------------------------------------------------------------------|

| Colorado                                                       |   | 84-0296600                           |
|----------------------------------------------------------------|--------|--------------------------------------|
| (State or other jurisdiction of incorporation or organization) |   | (I.R.S. Employer Identification No.) |

| o Large accelerated filer                |   | oAccelerated filer               |
|-----------------------------------------------|--------|----------------------------------|
|                                          |   |                             |
| x Non-accelerated filer                  |   | o Smaller Reporting Company |
| (Do not check if a smaller reporting company) |   |                             |

----

----

----

INDEX

|                                                                                                                              |   |
|-----------------------------------------------------------------------------------------------------------------------------------|--------|
| PART I                                                                                                                            | 3      |
| Item 1 — Business                                                                                                           | 3      |
| DEFINITION OF ABBREVIATIONS AND INDUSTRY TERMS                                                                                    | 3      |
| COMPANY OVERVIEW                                                                                                                  | 6      |
| ELECTRIC UTILITY OPERATIONS                                                                                                       | 6      |
| Overview                                                                                                                          | 6      |
| Public Utility Regulation                                                                                                         | 7      |
| Capacity and Demand                                                                                                               | 7      |
| Energy Sources and Related Transmission Initiatives                                                                               | 7      |
| Fuel Supply and Costs                                                                                                             | 9      |
| Fuel Sources                                                                                                                      | 10     |
| Wholesale Commodity Marketing Operations                                                                                          | 10     |
| Summary of Recent Regulatory Developments                                                                                         | 10     |
| Electric Operating Statistics                                                                                                     | 13     |
| NATURAL GAS UTILITY OPERATIONS                                                                                                    | 13     |
| Public Utility Regulation                                                                                                         | 13     |
| Capability and Demand                                                                                                             | 14     |
| Natural Gas Supply and Costs                                                                                                      | 14     |
| Natural Gas Operating Statistics                                                                                                  | 15     |
| ENVIRONMENTAL MATTERS                                                                                                             | 15     |
| EMPLOYEES                                                                                                                         | 15     |
| Item 1A — Risk Factors                                                                                                      | 16     |
| Item 1B — Unresolved Staff Comments                                                                                         | 23     |
| Item 2 — Properties                                                                                                         | 24     |
| Item 3 — Legal Proceedings                                                                                                  | 25     |
| Item 4 — Reserved                                                                                                           | 25     |
|                                                                                                                              |   |
| PART II                                                                                                                           | 25     |
| Item 5 — Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities | 25     |
| Item 6 — Selected Financial Data                                                                                            | 25     |
| Item 7 — Management’s Discussion and Analysis of Financial Condition and Results of Operations                        | 25     |
| Item 7A — Quantitative and Qualitative Disclosures About Market Risk                                                        | 28     |
| Item 8 — Financial Statements and Supplementary Data                                                                        | 30     |
| Item 9 — Changes in and Disagreements with Accountants on Accounting and Financial Disclosure                               | 76     |
| Item 9A — Controls and Procedures                                                                                           | 76     |
| Item 9B — Other Information                                                                                                 | 77     |
|                                                                                                                              |   |
| PART III                                                                                                                          | 77     |
| Item 10 — Directors, Executive Officers and Corporate Governance                                                            | 77     |
| Item 11 — Executive Compensation                                                                                            | 77     |
| Item 12 — Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters                    | 77     |
| Item 13 — Certain Relationships and Related Transactions, and Director Independence                                         | 77     |
| Item 14 — Principal Accountant Fees and Services                                                                            | 77     |
|                                                                                                                              |   |
| PART IV                                                                                                                           | 78     |
| Item 15 — Exhibits, Financial Statement Schedules                                                                           | 78     |
|                                                                                                                              |   |
| SIGNATURES                                                                                                                        | 82     |

----

Index

PART I

Item l — Business

| Xcel Energy Subsidiaries and Affiliates                |   |                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------|--------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| NCE                                                    |   | New Century Energies, Inc.                                                                                                                                                                                                                                                                                                                                                                                       |
| NSP-Minnesota                                          |   | Northern States Power Company, a Minnesota corporation                                                                                                                                                                                                                                                                                                                                                                |
| NSP-Wisconsin                                          |   | Northern States Power Company, a Wisconsin corporation                                                                                                                                                                                                                                                                                                                                                                |
| PSCo                                                   |   | Public Service Company of Colorado, a Colorado corporation                                                                                                                                                                                                                                                                                                                                                            |
| PSRI                                                   |   | P.S.R. Investments, Inc., a manager of corporate-owned life insurance policies                                                                                                                                                                                                                                                                                                                                   |
| SPS                                                    |   | Southwestern Public Service Company, a New Mexico corporation                                                                                                                                                                                                                                                                                                                                                         |
| utility subsidiaries                                   |   | NSP-Minnesota, NSP-Wisconsin, PSCo, SPS                                                                                                                                                                                                                                                                                                                                                                               |
| WYCO                                                   |   | WYCO Development LLC, a joint venture formed between Xcel Energy and  Colorado Interstate Gas Company to develop and lease natural gas pipeline, storage, and compression facilities                                                                                                                                                                                                                   |
| Xcel Energy                                            |   | Xcel Energy Inc., a Minnesota corporation                                                                                                                                                                                                                                                                                                                                                                             |
| Federal and State Regulatory Agencies                  |   |                                                                                                                                                                                                                                                                                                                                                                                                                  |
| AQCC                                                   |   | Colorado Air Quality Control Commission                                                                                                                                                                                                                                                                                                                                                                               |
| CAPCD                                                  |   | Colorado Air Pollution Control Division                                                                                                                                                                                                                                                                                                                                                                               |
| CPUC                                                   |   | Colorado Public Utilities Commission.  The state agency that regulates the retail rates, services and other aspects of PSCo’s operations in Colorado.  The CPUC also has jurisdiction over the capital structure and issuance of securities by PSCo.                                                                                                                                        |
| CSB                                                    |   | U.S. Chemical Safety Board                                                                                                                                                                                                                                                                                                                                                                                            |
| DOI                                                    |   | U.S. Department of the Interior                                                                                                                                                                                                                                                                                                                                                                                       |
| EPA                                                    |   | United States Environmental Protection Agency                                                                                                                                                                                                                                                                                                                                                                         |
| FERC                                                   |   | Federal Energy Regulatory Commission.  The U.S. agency that regulates the rates and services for transportation of electricity and natural gas; the sale of wholesale electricity, in interstate commerce, including the sale of electricity at market-based rates; hydroelectric generation licensing; and accounting requirements for utility holding companies, service companies, and public utilities. |
| IRS                                                    |   | Internal Revenue Service                                                                                                                                                                                                                                                                                                                                                                                              |
| NERC                                                   |   | North American Electric Reliability Corporation.  A self-regulatory organization, subject to oversight by the FERC and government authorities in Canada, to develop and enforce reliability standards.                                                                                                                                                                                                      |
| OCC                                                    |   | Office of Consumer Counsel                                                                                                                                                                                                                                                                                                                                                                                            |
| OSHA                                                   |   | Occupational Safety and Health Administration                                                                                                                                                                                                                                                                                                                                                                         |
| SEC                                                    |   | Securities and Exchange Commission                                                                                                                                                                                                                                                                                                                                                                                    |
| Electric, Purchased Gas and ResourceAdjustment Clauses |   |                                                                                                                                                                                                                                                                                                                                                                                                                  |
| DSM                                                    |   | Demand side management.  Energy conservation and weatherization program for low-income customers.                                                                                                                                                                                                                                                                                                           |
| DSMCA                                                  |   | Demand side management cost adjustment.  A clause permitting PSCo to recover demand side management costs over five years while non-labor incremental expenses and carrying costs associated with deferred DSM costs are recovered on an annual basis.  Costs for the low-income energy assistance program are recovered through the DSMCA.                                                       |
| ECA                                                    |   | Retail electric commodity adjustment.  Allows PSCo to recover its actual fuel and purchased energy expense in a calendar year to a benchmark formula.  Short-term sales margins and margins from the sale of SO2 allowances are shared with retail customers through the ECA.                                                                                                                     |
| GCA                                                    |   | Gas cost adjustment.  Allows PSCo to recover its actual costs of purchased natural gas and natural gas transportation.  The GCA is revised monthly to coincide with changes in purchased gas costs.                                                                                                                                                                                               |
| PCCA                                                   |   | Purchased capacity cost adjustment.  Allows PSCo to recover from retail customers for all purchased capacity payments to power suppliers.  Capacity charges are not included in PSCo’s electric rates or other recovery mechanisms.                                                                                                                                                         |

----

Index

| PDRA                          |   | Partial Decoupling Rate Adjustment.  A clause included in PSCo’s retail natural gas schedules that recovers revenue lost to decreasing use per customer beyond a threshold.                                                                                                                                                                                           |
|-------------------------------|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| QSP                           |   | Quality of service plan.  Provides for bill credits to retail customers if the utility does not achieve certain operational performance targets and/or specific capital investments for reliability.  The current QSP for the PSCo electric utility provides for bill credits to customers based on operational performance standards through Dec. 31, 2012. |
| RES                           |   | Renewable energy standard                                                                                                                                                                                                                                                                                                                                                             |
| RESA                          |   | Renewable energy standard adjustment                                                                                                                                                                                                                                                                                                                                                  |
| SCA                           |   | Steam cost adjustment.  Allows PSCo to recover the difference between its actual cost of fuel and the amount of these costs recovered under its base steam service rates.  The SCA is revised annually to coincide with changes in fuel costs.                                                                                                                    |
| TCA                           |   | Transmission cost adjustment.  Provides for the recovery of transmission plant revenue requirements.                                                                                                                                                                                                                                                                        |
| Other Terms and Abbreviations |   |                                                                                                                                                                                                                                                                                                                                                                                  |
| AFUDC                         |   | Allowance for funds used during construction.  Defined in regulatory accounts as non-cash accounting convention that represents the estimated composite interest costs of debt and a return on equity funds used to finance construction.  The allowance is capitalized in property accounts and included in income.                                              |
| ALJ                           |   | Administrative law judge.  A judge presiding over regulatory proceedings.                                                                                                                                                                                                                                                                                                   |
| APBO                          |   | Accumulated Postretirement Benefit Obligation                                                                                                                                                                                                                                                                                                                                         |
| ARO                           |   | Asset retirement obligation.  Obligations associated with the retirement of tangible long-lived assets and the associated asset retirement costs.                                                                                                                                                                                                                           |
| ASC                           |   | FASB Accounting Standards Codification                                                                                                                                                                                                                                                                                                                                                |
| BAL                           |   | Balancing authority                                                                                                                                                                                                                                                                                                                                                                   |
| BART                          |   | Best Available Retrofit Technology                                                                                                                                                                                                                                                                                                                                                    |
| BTA                           |   | Best Technology Available                                                                                                                                                                                                                                                                                                                                                             |
| CAA                           |   | Clean Air Act                                                                                                                                                                                                                                                                                                                                                                         |
| CACJA                         |   | Clean Air Clean Jobs Act                                                                                                                                                                                                                                                                                                                                                              |
| CAMR                          |   | Clean Air Mercury Rule                                                                                                                                                                                                                                                                                                                                                                |
| CIPS                          |   | Critical Infrastructure Protection Standards                                                                                                                                                                                                                                                                                                                                          |
| CO2                           |   | Carbon dioxide                                                                                                                                                                                                                                                                                                                                                                        |
| COLI                          |   | Corporate-owned life insurance                                                                                                                                                                                                                                                                                                                                                        |
| Codification                  |   | FASB Accounting Standards Codification                                                                                                                                                                                                                                                                                                                                                |
| CPCN                          |   | Certificate of Public Convenience and Necessity                                                                                                                                                                                                                                                                                                                                       |
| CWIP                          |   | Construction work in progress                                                                                                                                                                                                                                                                                                                                                         |
| derivative instrument         |   | A financial instrument or other contract with all three of the following characteristics:                                                                                                                                                                                                                                                                                             |
|                          |   | ●                                                                                                                                                                                                                                                                                                                                                                               | An underlying and a notional amount or payment provision or both; |
|                          |   | ●                                                                                                                                                                                                                                                                                                                                                                               | Requires no initial investment or an initial net investment that is smaller than would be required for other types of contracts that would be expected to have a similar response to changes in market factors; and |
|                          |   | ●                                                                                                                                                                                                                                                                                                                                                                               | Terms require or permit a net settlement, can be readily settled net by means outside the contract or provide for delivery of an asset that puts the recipient in a position not substantially different from net settlement. |
| distribution                  |   | The system of lines, transformers, switches and mains that connect electric and natural gas transmission systems to customers.                                                                                                                                                                                                                                                        |
| ETR                           |   | Effective tax rate                                                                                                                                                                                                                                                                                                                                                                    |
| FASB                          |   | Financial Accounting Standards Board                                                                                                                                                                                                                                                                                                                                                  |
| GAAP                          |   | Generally accepted accounting principles                                                                                                                                                                                                                                                                                                                                              |
| generation                    |   | The process of transforming other forms of energy, such as nuclear or fossil fuels, into electricity.  Also, the amount of electric energy produced, expressed in MW (capacity) or MW hours (energy).                                                                                                                                                                       |
| GHG                           |   | Greenhouse gas                                                                                                                                                                                                                                                                                                                                                                        |
| JOA                           |   | Joint operating agreement among Xcel Energy’s utility subsidiaries                                                                                                                                                                                                                                                                                                              |
| LIBOR                         |   | London Interbank Offered Rate                                                                                                                                                                                                                                                                                                                                                         |
| MACT                          |   | Maximum Achievable Control Technology                                                                                                                                                                                                                                                                                                                                                 |
| mark-to-market                |   | The process whereby an asset or liability is recognized at fair value.                                                                                                                                                                                                                                                                                                                |
| MISO                          |   | Midwest Independent Transmission System Operator                                                                                                                                                                                                                                                                                                                                      |
| Moody’s                 |   | Moody’s Investor Services                                                                                                                                                                                                                                                                                                                                                       |

----

Index

| native load                      |   | The customer demand of retail and wholesale customers whereby a utility has an obligation to serve: e.g., an obligation to provide electric or natural gas service created by statute or long-term contract.                                                            |
|----------------------------------|--------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| natural gas                      |   | A naturally occurring mixture of hydrocarbon and non-hydrocarbon gases found in porous geological formations beneath the earth’s surface, often in association with petroleum.  The principal constituent is methane.                                   |
| NAV                              |   | Notice of alleged violation                                                                                                                                                                                                                                             |
| NOx                              |   | Nitrogen oxide                                                                                                                                                                                                                                                          |
| nonutility                       |   | All items of revenue, expense and investment not associated, either by direct assignment or by allocation, with providing service to the utility customer.                                                                                                              |
| NOPR                             |   | Notice of proposed rulemaking                                                                                                                                                                                                                                           |
| O&M                          |   | Operating and maintenance                                                                                                                                                                                                                                               |
| OCI                              |   | Other comprehensive income                                                                                                                                                                                                                                              |
| PBRP                             |   | Performance-based regulatory plan.  An annual electric earnings test, an electric quality of service plan and a natural gas quality of service plan established by the CPUC.                                                                                  |
| PCB                              |   | Polychlorinated biphenyl                                                                                                                                                                                                                                                |
| PJM                              |   | PJM Interconnection, LLC                                                                                                                                                                                                                                                |
| PPA                              |   | Purchased power agreement                                                                                                                                                                                                                                               |
| Provident                        |   | Provident Life & Accident Insurance Company                                                                                                                                                                                                                         |
| PRP                              |   | Potentially responsible party                                                                                                                                                                                                                                           |
| PV                               |   | Photovoltaic                                                                                                                                                                                                                                                            |
| rate base                        |   | The investor-owned plant facilities for generation, transmission and distribution and other assets used in supplying utility service to the consumer.                                                                                                                   |
| REC                              |   | Renewable energy credit                                                                                                                                                                                                                                                 |
| RFP                              |   | Request for proposal                                                                                                                                                                                                                                                    |
| ROE                              |   | Return on equity                                                                                                                                                                                                                                                        |
| ROFR                             |   | Right of first refusal                                                                                                                                                                                                                                                  |
| RPS                              |   | Renewable Portfolio Standard.  A regulation that requires the increased production of energy from renewable energy sources, such as wind, solar, biomass, and geothermal.                                                                                     |
| RTO                              |   | Regional Transmission Organization.  An independent entity, which is established to have “functional control” over a utility’s electric transmission systems, in order to provide non-discriminatory access to transmission of electricity. |
| SCR                              |   | Selective Catalytic Reduction                                                                                                                                                                                                                                           |
| SIP                              |   | State Implementation Plan                                                                                                                                                                                                                                               |
| SO2                              |   | Sulfur dioxide                                                                                                                                                                                                                                                          |
| Standard & Poor’s |   | Standard & Poor’s Ratings Services                                                                                                                                                                                                                       |
| unbilled revenues                |   | Amount of service rendered but not billed at the end of an accounting period.  Cycle meter-reading practices result in unbilled consumption between the date of last meter reading and the end of the period.                                                 |
| Underlying                       |   | A specified interest rate, security price, commodity price, foreign exchange rate, index of prices or rates, or other variable, including the occurrence or nonoccurrence of a specified event such as a scheduled payment under a contract.                            |
| WECC                             |   | Western Electricity Coordinating Council                                                                                                                                                                                                                                |
| wheeling or transmission         |   | An electric service wherein high voltage transmission facilities of one utility system are used to transmit power generated within or purchased from another system.                                                                                                    |
| Measurements                     |   |                                                                                                                                                                                                                                                                    |
| Btu                              |   | British thermal unit.  A standard unit for measuring thermal energy or heat commonly used as a gauge for the energy content of natural gas and other fuels.                                                                                                   |
| KV                               |   | Kilovolts (one KV equals one thousand volts)                                                                                                                                                                                                                            |
| KW                               |   | Kilowatts (one KW equals one thousand watts)                                                                                                                                                                                                                            |
| KWh                              |   | Kilowatt hours                                                                                                                                                                                                                                                          |
| MMBtu                            |   | One million Btus                                                                                                                                                                                                                                                        |
| MW                               |   | Megawatts (one MW equals one thousand KW)                                                                                                                                                                                                                               |
| Volt                             |   | The unit of measurement of electromotive force.  Equivalent to the force required to produce a current of one ampere through a resistance of one ohm.  The unit of measure for electrical potential.  Generally measured in kilovolts.    |
| Watt                             |   | A measure of power production or usage.                                                                                                                                                                                                                                 |

----

Index

COMPANY OVERVIEW

ELECTRIC UTILITY OPERATIONS

Overview

----

Index

Public Utility Regulation

| ● | ECA — The ECA recovers fuel and purchase power costs.  Short-term sales margins and margins from the sale of SO2 allowances are shared with retail customers through the ECA.  The ECA mechanism is revised quarterly. |
|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PCCA — The PCCA allows for recovery of purchased capacity payments for power purchase agreements.  Effective January 2011, the PCCA recovers the revenue requirement associated with the purchase of two facilities formerly under power purchase agreement:  Blue Spruce Energy Center and Rocky Mountain Energy Center. |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | SCA — The SCA allows PSCo to recover the difference between its actual cost of fuel and the amount of these costs recovered under its base steam service rates.  The SCA rate is revised annually on January 1, as well as on an interim basis to coincide with changes in fuel costs. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | DSMCA — The DSMCA clause permits PSCo to recover DSM and interruptible service option credit costs on a concurrent basis and performance initiatives based on achieving various energy savings goals.  Beginning 2010, the CPUC approved recovery of the full amount of DSM-related costs through the combination of base rates and a DSMCA tracker mechanism. |
|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | RESA — The RESA recovers the incremental costs of compliance with the RES and is set at its maximum level of 2 percent of the customer’s total bill. |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | Wind Source Service — The Wind Source Service is a premium service for those customers who voluntarily choose to contribute funds for the acquisition of additional renewable resources beyond the level of PSCo’s resource plan.  Wind Energy Service customers pay a charge that is in addition to the rates paid by other customers. |
|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | TCA — The TCA provides for the recovery outside of rate cases of transmission plant revenue requirements and allows for a return on CWIP for transmission investments. |
|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

Capacity and Demand

|                       |   |   |   |   |   |   |   |
|----------------------------|--------|--------|--------|--------|--------|--------|--------|
| System Peak Demand (in MW) |   |
| 2008                       |   |   | 2009   |   |   | 2010   |   |   | 2011 Forecast |   |
|                       | 6,903  |   |   |   | 6,258  |   |   |   | 6,401 |   |   |   | 6,521 |   |

Energy Sources and Related Transmission Initiatives

----

Index

|   | ● | At least 12 percent of its retail sales for the years 2011 through 2014; |
|--------|---------|--------------------------------------------------------------------------|

|   | ● | At least 20 percent of its retail sales for the years 2015 through 2019; and |
|--------|---------|------------------------------------------------------------------------------|

|   | ● | At least 30 percent of its retail sales for the years 2020 and thereafter. |
|--------|---------|----------------------------------------------------------------------------|

|   | ● | At least 1 percent of retail sales in the years 2011 and 2012 and 1.25 percent of retail sales in the years 2013 and 2014; |
|--------|---------|----------------------------------------------------------------------------------------------------------------------------|

|   | ● | At least 1.75 percent of retail sales in the years 2015 and 2016 and 2 percent of retail sales in the years 2017, 2018 and 2019; and |
|--------|---------|--------------------------------------------------------------------------------------------------------------------------------------|

|   | ● | At least 3 percent of retail sales in the years 2020 and thereafter. |
|--------|---------|----------------------------------------------------------------------|

----

Index

|   | ● | Shutdown Cherokee Units 1 and 2 in 2011 and Cherokee Unit 3 (365 MW in total) by the end of 2015, after a new natural gas combined-cycle unit is built at Cherokee Station (569 MW); |
|--------|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | ● | Fuel-switch Cherokee Unit 4 (352 MW) to natural gas by 2017; |
|--------|---------|--------------------------------------------------------------|

|   | ● | Shutdown Arapahoe Unit 3 (45 MW) and fuel-switch Unit 4 (352 MW) in 2013 to natural gas; |
|--------|---------|------------------------------------------------------------------------------------------|

|   | ● | Shutdown Valmont Unit 5 (186 MW) in 2017; |
|--------|---------|-------------------------------------------|

|   | ● | Install SCR for controlling NOx and a scrubber for controlling SO2 on Pawnee Station in 2014; |
|--------|---------|-----------------------------------------------------------------------------------------------|

|   | ● | Install SCR on Hayden Unit 1 in 2015 and Hayden Unit 2 in 2016; and |
|--------|---------|---------------------------------------------------------------------|

|   | ● | Convert Cherokee Unit 2 and Arapahoe Unit 3 to synchronous condensers to support the transmission system. |
|--------|---------|-----------------------------------------------------------------------------------------------------------|

Fuel Supply and Costs

|   |   |   |   |   |        |   |   |    |   |   |    |   |   | Weighted  |   |
|--------|--------|--------|--------|--------|-------------|--------|--------|---------|--------|--------|---------|--------|--------|-----------|--------|
|   |   | Coal   |   |   | Natural Gas |   |   | Average |   |
|   |   | Cost   |   |   | Percent     |   |   | Cost    |   |   | Percent |   |   | Fuel Cost |   |
| 2010   |   | $      | 1.58   |   |        |   | 85     | %       |   | $      | 5.05    |   |   |      | 15     | % |   | $ | 2.11 |   |
| 2009   |   |   | 1.52   |   |        |   | 82     |    |   |   | 3.99    |   |   |      | 18     |   |   |   | 1.97 |   |
| 2008   |   |   | 1.42   |   |        |   | 84     |    |   |   | 7.03    |   |   |      | 16     |   |   |   | 2.31 |   |

----

Index

Fuel Sources

Wholesale Commodity Marketing Operations

Summary of Recent Federal Regulatory Developments

----

Index

----

Index

----

Index

Electric Operating Statistics

|                                      |   |                |      |         |   |   |      |         |   |   |
|-------------------------------------------|--------|---------------------|-----------|--------------|--------|--------|-----------|--------------|--------|--------|
|                                      |   | Year Ended Dec. 31, |      |
|                                      |   | 2010                |      |         | 2009   |   |      | 2008         |   |
| Electric sales (Millions of KWh)          |   |                |      |         |   |   |      |         |   |
| Residential                               |   |                | 9,087     |         |   |   | 8,715     |         |   |   | 8,905 |   |
| Commercial and industrial                 |   |                | 18,984    |         |   |   | 18,448    |         |   |   | 19,137 |   |
| Public authorities and other              |   |                | 227       |         |   |   | 226       |         |   |   | 229 |   |
| Total retail                              |   |                | 28,298    |         |   |   | 27,389    |         |   |   | 28,271 |   |
| Sales for resale                          |   |                | 7,079     |         |   |   | 6,949     |         |   |   | 7,756 |   |
| Total energy sold                         |   |                | 35,377    |         |   |   | 34,338    |         |   |   | 36,027 |   |
|                                      |   |                |      |         |   |   |      |         |   |   |   |   |
| Number of customers at end of period      |   |                |      |         |   |   |      |         |   |   |   |   |
| Residential                               |   |                | 1,159,287 |         |   |   | 1,150,181 |         |   |   | 1,142,106 |   |
| Commercial and industrial                 |   |                | 152,671   |         |   |   | 151,637   |         |   |   | 150,826 |   |
| Public authorities and other              |   |                | 56,837    |         |   |   | 58,371    |         |   |   | 58,195 |   |
| Total retail                              |   |                | 1,368,795 |         |   |   | 1,360,189 |         |   |   | 1,351,127 |   |
| Wholesale                                 |   |                | 26        |         |   |   | 30        |         |   |   | 35 |   |
| Total customers                           |   |                | 1,368,821 |         |   |   | 1,360,219 |         |   |   | 1,351,162 |   |
|                                      |   |                |      |         |   |   |      |         |   |   |   |   |
| Electric revenues (Thousands of Dollars)  |   |                |      |         |   |   |      |         |   |   |   |   |
| Residential                               |   | $                   | 1,013,188 |         |   | $      | 862,242   |         |   | $      | 914,531 |   |
| Commercial and industrial                 |   |                | 1,552,116 |         |   |   | 1,309,770 |         |   |   | 1,514,652 |   |
| Public authorities and other              |   |                | 48,847    |         |   |   | 44,434    |         |   |   | 44,066 |   |
| Total retail                              |   |                | 2,614,151 |         |   |   | 2,216,446 |         |   |   | 2,473,249 |   |
| Wholesale                                 |   |                | 368,396   |         |   |   | 349,909   |         |   |   | 457,623 |   |
| Other electric revenues                   |   |                | 72,498    |         |   |   | 112,223   |         |   |   | 52,057 |   |
| Total electric revenues                   |   | $                   | 3,055,045 |         |   | $      | 2,678,578 |         |   | $      | 2,982,929 |   |
|                                      |   |                |      |         |   |   |      |         |   |   |   |   |
| KWh sales per retail customer             |   |                | 20,674    |         |   |   | 20,136    |         |   |   | 20,924 |   |
| Revenue per retail customer               |   | $                   | 1,910     |         |   | $      | 1,630     |         |   | $      | 1,831 |   |
| Residential revenue per KWh               |   |                | 11.15     |  ¢ |   |   | 9.89      |  ¢ |   |   | 10.27 |  ¢ |
| Commercial and industrial revenue per KWh |   |                | 8.18      |         |   |   | 7.10      |         |   |   | 7.91 |   |
| Wholesale revenue per KWh                 |   |                | 5.20      |         |   |   | 5.04      |         |   |   | 5.90 |   |

NATURAL GAS UTILITY OPERATIONS

Public Utility Regulation

----

Index

| ● | GCA — The GCA mechanism allows PSCo to recover its actual costs of purchased gas and transportation to meet the requirements of its customers.  The GCA is revised quarterly to allow for changes in gas rates. |
|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | DSMCA — PSCo has a low-income energy assistance program.  The costs of this energy conservation and weatherization program are recovered through the gas DSMCA. |
|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PDRA — The PDRA recovers revenue lost to decreasing use per customer beyond a threshold.  No revenue is currently recovered through this clause. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| 2010 |   | $      | 5.10       |   |
|------|--------|--------|------------|--------|
| 2009 |   |   | 5.13       |   |
| 2008 |   |   |  7.04 |   |

----

Index

Natural Gas Operating Statistics

|                                        |   |                |      |         |   |   |      |
|---------------------------------------------|--------|---------------------|-----------|--------------|--------|--------|-----------|
|                                        |   | Year Ended Dec. 31, |      |
|                                        |   | 2010                |      |         | 2009   |   |      | 2008 |   |
| Natural gas deliveries (Thousands of MMBtu) |   |                |      |         |   |   |      |   |   |
| Residential                                 |   |                | 95,231    |         |   |   | 95,566    |   |   |   | 96,871 |   |
| Commercial and industrial                   |   |                | 39,399    |         |   |   | 39,878    |   |   |   | 41,121 |   |
| Total retail                                |   |                | 134,630   |         |   |   | 135,444   |   |   |   | 137,992 |   |
| Transportation and other                    |   |                | 101,597   |         |   |   | 109,906   |   |   |   | 115,923 |   |
| Total deliveries                            |   |                | 236,227   |         |   |   | 245,350   |   |   |   | 253,915 |   |
|                                        |   |                |      |         |   |   |      |   |   |   |   |   |
| Number of customers at end of period        |   |                |      |         |   |   |      |   |   |   |   |   |
| Residential                                 |   |                | 1,200,950 |         |   |   | 1,193,418 |   |   |   | 1,186,255 |   |
| Commercial and industrial                   |   |                | 99,866    |         |   |   | 99,654    |   |   |   | 99,425 |   |
| Total retail                                |   |                | 1,300,816 |         |   |   | 1,293,072 |   |   |   | 1,285,680 |   |
| Transportation and other                    |   |                | 5,240     |         |   |   | 4,789     |   |   |   | 4,313 |   |
| Total customers                             |   |                | 1,306,056 |         |   |   | 1,297,861 |   |   |   | 1,289,993 |   |
|                                        |   |                |      |         |   |   |      |   |   |   |   |   |
| Natural gas revenues (Thousands of Dollars) |   |                |      |         |   |   |      |   |   |   |   |   |
| Residential                                 |   | $                   | 736,160   |         |   | $      | 745,728   |   |   | $ | 941,077 |   |
| Commercial and industrial                   |   |                | 274,288   |         |   |   | 285,199   |   |   |   | 368,143 |   |
| Total retail                                |   |                | 1,010,448 |         |   |   | 1,030,927 |   |   |   | 1,309,220 |   |
| Transportation and other                    |   |                | 64,998    |         |   |   | 63,032    |   |   |   | 64,512 |   |
| Total natural gas revenues                  |   | $                   | 1,075,446 |         |   | $      | 1,093,959 |   |   | $ | 1,373,732 |   |
|                                        |   |                |      |         |   |   |      |   |   |   |   |   |
| MMBtu sales per retail customer             |   |                | 103.50    |         |   |   | 104.75    |   |   |   | 107.33 |   |
| Revenue per retail customer                 |   | $                   | 777       |         |   | $      | 797       |   |   | $ | 1,018 |   |
| Residential revenue per MMBtu               |   |                | 7.73      |  ¢ |   |   | 7.80      |  ¢ |   |   | 9.71 |  ¢ |
| Commercial and industrial revenue per MMBtu |   |                | 6.96      |         |   |   | 7.15      |   |   |   | 8.95 |   |
| Transportation and other revenue per MMBtu  |   |                | 0.64      |         |   |   | 0.57      |   |   |   | 0.56 |   |

ENVIRONMENTAL MATTERS

EMPLOYEES

----

Index

Item 1A — Risk Factors

----

Index

| ● | Sites of former MGPs operated by us, our predecessors, or other entities; and |
|---------|-------------------------------------------------------------------------------|

| ● | Third party sites, such as landfills, for which we are alleged to be a potentially responsible party that sent hazardous materials and wastes. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

----

Index

----

Index

----

Index

----

Index

----

Index

Item 1B — Unresolved Staff Comments

----

Index

Item 2 — Properties

|                                       |   |   |        |   |      |   |      |            |   |           |   |
|--------------------------------------------|--------|--------|-------------|--------|-----------|--------|-----------|-----------------|--------|----------------|--------|
| PSCo                                       |   |   |        |   |      |   |      |            |   | Summer 2010    |   |
|                                       |   |   |        |   |      |   |      |            |   | Net Dependable |   |
| Station, Location and Unit                 |   | Fuel   |        |   | Installed |   |      | Capability (MW) |   |
| Steam:                                     |   |   |        |   |      |   |      |            |   |           |   |
| Arapahoe-Denver, Colo., 2 Units            |   |   | Coal        |   |      |   | 1951-1955 |            |   |           | 153    |   |
| Cherokee-Denver, Colo., 4 Units            |   |   | Coal        |   |      |   | 1957-1968 |            |   |           | 717    |   |
| Comanche-Pueblo, Colo., 3 Units            |   |   | Coal        |   |      |   | 1973-2010 |            |   |           | 1,171  |  (a) |
| Craig-Craig, Colo., 2 Units                |   |   | Coal        |   |      |   | 1979-1980 |            |   |           | 83     |  (b) |
| Hayden-Hayden, Colo., 2 Units              |   |   | Coal        |   |      |   | 1965-1976 |            |   |           | 237    |  (c) |
| Pawnee-Brush, Colo.                        |   |   | Coal        |   |      |   | 1981      |            |   |           | 505    |   |
| Valmont-Boulder, Colo.                     |   |   | Coal        |   |      |   | 1964      |            |   |           | 184    |   |
| Zuni-Denver, Colo., 2 Units                |   |   | Coal        |   |      |   | 1948-1954 |            |   |           | 65     |   |
| Combustion Turbine:                        |   |   |        |   |      |   |      |            |   |           |   |   |
| Blue Spruce-Aurora, Colo., 2 Units         |   |   | Natural Gas |   |      |   | 2003      |            |   |           | 278    |  (e) |
| Fort St. Vrain-Platteville, Colo., 6 Units |   |   | Natural Gas |   |      |   | 1972-2009 |            |   |           | 969    |   |
| Rocky Mountain-Keenesburg, Colo., 3 Units  |   |   | Natural Gas |   |      |   | 2004      |            |   |           | 601    |  (e) |
| Various locations, 6 Units                 |   |   | Natural Gas |   |      |   | Various   |            |   |           | 174    |   |
| Hydro:                                     |   |   |        |   |      |   |      |            |   |           |   |   |
| Cabin Creek-Georgetown, Colo.              |   |   |        |   |      |   |      |            |   |           |   |   |
| Pumped Storage, 2 Units                    |   |   | Hydro       |   |      |   | 1967      |            |   |           | 210    |   |
| Various locations, 9 Units                 |   |   | Hydro       |   |      |   | Various   |            |   |           | 26     |   |
| Wind:                                      |   |   |        |   |      |   |      |            |   |           |   |   |
| Ponnequin-Weld County, Colo.               |   |   | Wind        |   |      |   | 1999-2001 |            |   |           | 25     |  (d) |
| Diesel:                                    |   |   |        |   |      |   |      |            |   |           |   |   |
| Cherokee-Denver, Colo., 2 Units            |   |   | Diesel      |   |      |   | 1967      |            |   |           | 6      |   |
|                                       |   |   |        |   |      |   | Total     |            |   |           | 5,404  |   |

| (a) | Construction of Comanche Unit 3, a 750 MW coal-fired unit, was completed in 2010.  PSCo owns two-thirds of the completed unit. |
|-----|------------------------------------------------------------------------------------------------------------------------------------------|

| (b) | Based on PSCo’s ownership interest of 10 percent. |
|-----|---------------------------------------------------------|

| (c) | Based on PSCo’s ownership interest of 76 percent of Unit 1 and 37 percent of Unit 2. |
|-----|--------------------------------------------------------------------------------------------|

| (d) | Amount represents nameplate rating capacity. |
|-----|----------------------------------------------|

| (e) | PSCo completed its acquisition of Blue Spruce Energy Center and Rocky Mountain Energy Center in December 2010.  See Note 18 to the consolidated financial statements for further information. |
|-----|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Conductor Miles  |   |   |   |
|------------------|--------|--------|--------|
| 345 KV           |   |   | 1,614  |   |
| 230 KV           |   |   | 11,519 |   |
| 138 KV           |   |   | 92     |   |
| 115 KV           |   |   | 4,882  |   |
| Less than 115 KV |   |   | 72,946 |   |

|         |   |   |   |
|--------------|--------|--------|--------|
| Miles        |   |   |   |
| Transmission |   |   | 2,301  |   |
| Distribution |   |   | 21,302 |   |

----

Index

Item 3 — Legal Proceedings

Item 4 — Reserved

Item 5 — Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer 

| ● | PSCo’s credit facility includes a financial covenant that requires the equity-to-total capitalization ratio to be greater than or equal to 35 percent.  PSCo was in compliance as its equity-to-total capitalization ratio was 54 percent and 56 percent at Dec. 31, 2010 and 2009, respectively. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | Dividends are also subject to the FERC’s jurisdiction under the Federal Power Act, which prohibits the payment of dividends out of capital accounts; payment of dividends is allowed out of retained earnings only. |
|---------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (Thousands of Dollars) |   | 2010   |   |   | 2009   |   |
|------------------------|--------|--------|--------|--------|--------|--------|
| First quarter          |   | $      | 66,655 |   |   | $      | 66,816 |   |
| Second quarter         |   |   | 66,729 |   |   |   | 65,960 |   |
| Third quarter          |   |   | 66,600 |   |   |   | 65,995 |   |
| Fourth quarter         |   |   | 66,828 |   |   |   | 65,822 |   |

Item 7 — Management’s Discussion and Analysis

----

Index

| (Millions of Dollars)             |   | 2010   |   |   | 2009   |   |
|-----------------------------------|--------|--------|--------|--------|--------|--------|
| Electric revenues                 |   | $      | 3,055  |   |   | $      | 2,679 |   |
| Electric fuel and purchased power |   |   | (1,513 | )      |   |   | (1,400 | ) |
| Electric margin                   |   | $      | 1,542  |   |   | $      | 1,279 |   |

| Electric Revenues                                        |   |          |   |
|----------------------------------------------------------|--------|---------------|--------|
| (Millions of Dollars)                                    |   | 2010 vs. 2009 |   |
| Retail rate increase                                     |   | $             | 155    |   |
| Fuel and purchased power cost recovery                   |   |          | 93     |   |
| Renewable energy credit sales                            |   |          | 33     |   |
| Phase II and seasonal rates                              |   |          | 31     |   |
| DSM revenue and incentive (partially offset by expenses) |   |          | 21     |   |
| Estimated impact of weather                              |   |          | 15     |   |
| Trading                                                  |   |          | 6      |   |
| Transmission revenues                                    |   |          | 6      |   |
| Retail sales increase (excluding weather impact)         |   |          | 6      |   |
| Other, net                                               |   |          | 10     |   |
| Total increase in electric revenues                      |   | $             | 376    |   |

----

Index

| (Millions of Dollars)                                    |   | 2010 vs. 2009 |   |
|----------------------------------------------------------|--------|---------------|--------|
| Retail rate increase                                     |   | $             | 155    |   |
| Phase II and seasonal rates                              |   |          | 31     |   |
| DSM revenue and incentive (partially offset by expenses) |   |          | 21     |   |
| Estimated impact of weather                              |   |          | 15     |   |
| Renewable energy credit sales                            |   |          | 14     |   |
| Firm wholesale                                           |   |          | 8      |   |
| Retail sales increase (excluding weather impact)         |   |          | 6      |   |
| Transmission revenues                                    |   |          | 6      |   |
| Trading                                                  |   |          | (7     | ) |
| Other, net                                               |   |          | 14     |   |
| Total increase in electric margin                        |   | $             | 263    |   |

|                                     |   |   |   |   |   |   |
|------------------------------------------|--------|--------|--------|--------|--------|--------|
| (Millions of Dollars)                    |   | 2010   |   |   | 2009   |   |
| Natural gas revenues                     |   | $      | 1,075  |   |   | $      | 1,094 |   |
| Cost of natural gas sold and transported |   |   | (685   | )      |   |   | (712 | ) |
| Natural gas margin                       |   | $      | 390    |   |   | $      | 382 |   |

|                                                     |   |          |   |
|----------------------------------------------------------|--------|---------------|--------|
| (Millions of Dollars)                                    |   | 2010 vs. 2009 |   |
| Purchased natural gas adjustment clause recovery         |   | $             | (27    | ) |
| Estimated impact of weather                              |   |          | (1     | ) |
| DSM revenue and incentive (partially offset by expenses) |   |          | 7      |   |
| Other, net                                               |   |          | 2      |   |
| Total decrease in natural gas revenues                   |   | $             | (19    | ) |

|                                                     |   |          |   |
|----------------------------------------------------------|--------|---------------|--------|
| (Millions of Dollars)                                    |   | 2010 vs. 2009 |   |
| DSM revenue and incentive (partially offset by expenses) |   | $             | 7      |   |
| Estimated impact of weather                              |   |          | (1     | ) |
| Other, net                                               |   |          | 2      |   |
| Total increase in natural gas margin                     |   | $             | 8      |   |

----

Index

|                                                 |   |          |   |
|------------------------------------------------------|--------|---------------|--------|
| (Millions of Dollars)                                |   | 2010 vs. 2009 |   |
| Higher plant generation costs                        |   | $             | 20     |   |
| Higher contract labor costs                          |   |          | 11     |   |
| Higher labor costs                                   |   |          | 7      |   |
| Higher information technology costs                  |   |          | 6      |   |
| Higher material costs                                |   |          | 4      |   |
| Lower employee benefit costs                         |   |          | (6     | ) |
| Other, net                                           |   |          | 6      |   |
| Total increase in operating and maintenance expenses |   | $             | 48     |   |

----

Index

|                                                                       |   |   |   |   |   |   |
|----------------------------------------------------------------------------|--------|--------|--------|--------|--------|--------|
| (Thousands of Dollars)                                                     |   | 2010   |   |   | 2009   |   |
| Fair value of commodity trading net contract assets outstanding at Jan. 1  |   | $      | 651    |   |   | $      | 554 |   |
| Contracts realized or settled during the period                            |   |   | 3,811  |   |   |   | (9,867 | ) |
| Commodity trading contract additions and changes during period             |   |   | (2,645 | )      |   |   | 9,964 |   |
| Fair value of commodity trading net contract assets outstanding at Dec. 31 |   | $      | 1,817  |   |   | $      | 651 |   |

|                   |   |                |   |   |                    |   |   |                |   |   |                |   |   |                              |    |   |                                   |   |    |   |   |   |   |   |
|------------------------|--------|---------------------|--------|--------|-------------------------|--------|--------|---------------------|--------|--------|---------------------|--------|--------|-----------------------------------|---------|--------|----------------------------------------|--------|---------|--------|--------|--------|--------|--------|
|                   |   | Futures / Forwards  |   |
| (Thousands of Dollars) |   | Source ofFair Value |   |   | MaturityLess Than1 Year |   |   | Maturity1 to 3Years |   |   | Maturity4 to 5Years |   |   |  MaturityGreater Than5 Years |    |   |  Total Futures/ForwardsFair Value |   |
| PSCo                   |   |                | 1      |   |                    |   | 572    |                |   |   | 1,245               |   |   |                              | — |   |                                   |   | — |   |   |   | 1,817  |   |

|                  |   |       |   |      |   |   |    |   |   |   |   |   |   |   |   |
|-----------------------|--------|------------|--------|-----------|--------|--------|---------|--------|--------|--------|--------|--------|--------|--------|--------|
|                  |   | Year Ended |   |      |   |   |    |   |   |   |   |   |   |   |   |
| (Millions of Dollars) |   | Dec. 31    |   | VaR Limit |   |   | Average |   |   | High   |   |   | Low    |   |
| 2010                  |   | $          | 0.15   |      |   | $      | 3.00    |   |   | $      | 0.22   |   |   | $      | 0.64   |   |   | $ | 0.03 |   |
| 2009                  |   |       | 0.50   |      |   |   | 5.00    |   |   |   | 0.44   |   |   |   | 2.02   |   |   |   | 0.06 |   |

----

Index

Item 8 — Financial Statements and Supplementary Data

----

Index

| /S/ DAVID L. EVES                     |   | /S/ DAVID M. SPARBY                        |
|---------------------------------------|--------|--------------------------------------------|
| David L. Eves                         |   | David M. Sparby                            |
| President and Chief Executive Officer |   | Vice President and Chief Financial Officer |
| February 28, 2011                |   | February 28, 2011                     |

----

Index

| /s/ DELOITTE & TOUCHE LLP |   |
|------------------------------------|--------|
| Minneapolis, Minnesota             |   |
| February 28, 2011             |   |

----

Index

|                                                                                                |   | Year Ended Dec. 31 |      |
|-----------------------------------------------------------------------------------------------------|--------|--------------------|-----------|
|                                                                                                |   | 2010               |      |   | 2009 |   |   | 2008 |   |
| Operating revenues                                                                                  |   |               |      |   |   |   |   |   |   |
| Electric                                                                                            |   | $                  | 3,055,045 |   |   | $ | 2,678,578 |   |   | $ | 2,982,929 |   |
| Natural gas                                                                                         |   |               | 1,075,446 |   |   |   | 1,093,959 |   |   |   | 1,373,732 |   |
| Steam and other                                                                                     |   |               | 33,879    |   |   |   | 35,772 |   |   |   | 36,383 |   |
| Total operating revenues                                                                            |   |               | 4,164,370 |   |   |   | 3,808,309 |   |   |   | 4,393,044 |   |
|                                                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Operating expenses                                                                                  |   |               |      |   |   |   |   |   |   |   |   |   |
| Electric fuel and purchased power                                                                   |   |               | 1,513,334 |   |   |   | 1,399,541 |   |   |   | 1,818,772 |   |
| Cost of natural gas sold and transported                                                            |   |               | 685,210   |   |   |   | 712,079 |   |   |   | 994,221 |   |
| Cost of sales — steam and other                                                               |   |               | 16,995    |   |   |   | 15,426 |   |   |   | 15,507 |   |
| Other operating and maintenance expenses                                                            |   |               | 677,359   |   |   |   | 628,999 |   |   |   | 605,008 |   |
| Demand side management program expenses                                                             |   |               | 128,939   |   |   |   | 104,919 |   |   |   | 32,990 |   |
| Depreciation and amortization                                                                       |   |               | 284,139   |   |   |   | 256,062 |   |   |   | 252,384 |   |
| Taxes (other than income taxes)                                                                     |   |               | 103,342   |   |   |   | 95,612 |   |   |   | 84,597 |   |
| Total operating expenses                                                                            |   |               | 3,409,318 |   |   |   | 3,212,638 |   |   |   | 3,803,479 |   |
|                                                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Operating income                                                                                    |   |               | 755,052   |   |   |   | 595,671 |   |   |   | 589,565 |   |
|                                                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Other income, net                                                                                   |   |               | 29,117    |   |   |   | 4,696 |   |   |   | 16,748 |   |
| Allowance for funds used during construction — equity                                         |   |               | 11,370    |   |   |   | 41,118 |   |   |   | 36,158 |   |
|                                                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Interest charges and financing costs                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Interest charges — includes other financing costs of $5,649, $5,686, and $5,754, respectively |   |               | 171,945   |   |   |   | 166,212 |   |   |   | 154,313 |   |
| Allowance for funds used during construction — debt                                           |   |               | (5,307    | ) |   |   | (18,452 | ) |   |   | (18,266 | ) |
| Total interest charges and financing costs                                                          |   |               | 166,638   |   |   |   | 147,760 |   |   |   | 136,047 |   |
|                                                                                                |   |               |      |   |   |   |   |   |   |   |   |   |
| Income before income taxes                                                                          |   |               | 628,901   |   |   |   | 493,725 |   |   |   | 506,424 |   |
| Income taxes                                                                                        |   |               | 229,181   |   |   |   | 170,405 |   |   |   | 166,628 |   |
| Net income                                                                                          |   | $                  | 399,720   |   |   | $ | 323,320 |   |   | $ | 339,796 |   |

----

Index

|                                                                          |   | Year Ended Dec. 31 |       |
|-------------------------------------------------------------------------------|--------|--------------------|------------|
|                                                                          |   | 2010               |       |   | 2009 |   |   | 2008 |   |
| Operating activities                                                          |   |               |       |   |   |   |   |   |   |
| Net income                                                                    |   | $                  | 399,720    |   |   | $ | 323,320 |   |   | $ | 339,796 |   |
| Adjustments to reconcile net income to cash provided by operating activities: |   |               |       |   |   |   |   |   |   |   |   |   |
| Depreciation and amortization                                                 |   |               | 289,050    |   |   |   | 260,935 |   |   |   | 260,873 |   |
| Demand side management program amortization                                   |   |               | 19,666     |   |   |   | 27,625 |   |   |   | 32,990 |   |
| Deferred income taxes                                                         |   |               | 154,861    |   |   |   | 197,348 |   |   |   | 85,875 |   |
| Amortization of investment tax credits                                        |   |               | (2,693     | ) |   |   | (2,375 | ) |   |   | (2,760 | ) |
| Allowance for equity funds used during construction                           |   |               | (11,370    | ) |   |   | (41,118 | ) |   |   | (36,158 | ) |
| Provision for bad debts                                                       |   |               | 21,571     |   |   |   | 21,189 |   |   |   | 28,372 |   |
| Net realized and unrealized hedging and derivative transactions               |   |               | (23,112    | ) |   |   | 42,896 |   |   |   | (19,012 | ) |
| Changes in operating assets and liabilities:                                  |   |               |       |   |   |   |   |   |   |   |   |   |
| Accounts receivable                                                           |   |               | 16,807     |   |   |   | 7,082 |   |   |   | (10,469 | ) |
| Accrued unbilled revenues                                                     |   |               | 16,418     |   |   |   | 40,573 |   |   |   | 5,665 |   |
| Inventories                                                                   |   |               | 34,424     |   |   |   | (19,700 | ) |   |   | (24,028 | ) |
| Prepayments and other                                                         |   |               | 14,328     |   |   |   | (44,555 | ) |   |   | 3,438 |   |
| Accounts payable                                                              |   |               | (106,632   | ) |   |   | (32,982 | ) |   |   | (607 | ) |
| Net regulatory assets and liabilities                                         |   |               | 17,098     |   |   |   | (64,251 | ) |   |   | 74,944 |   |
| Other current liabilities                                                     |   |               | 16,067     |   |   |   | (1,531 | ) |   |   | 3,700 |   |
| Pension and employee benefit obligation                                       |   |               | (29,820    | ) |   |   | (216,696 | ) |   |   | (63,643 | ) |
| Change in other noncurrent assets                                             |   |               | (2,578     | ) |   |   | 375 |   |   |   | 436 |   |
| Change in other noncurrent liabilities                                        |   |               | (11,474    | ) |   |   | (24,796 | ) |   |   | 15,900 |   |
| Net cash provided by operating activities                                     |   |               | 812,331    |   |   |   | 473,339 |   |   |   | 695,312 |   |
|                                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Investing activities                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Utility capital/construction expenditures                                     |   |               | (571,746   | ) |   |   | (627,421 | ) |   |   | (809,738 | ) |
| Allowance for equity funds used during construction                           |   |               | 11,370     |   |   |   | 41,118 |   |   |   | 36,158 |   |
| Acquisition of generation assets                                              |   |               | (732,495   | ) |   |   | — |   |   |   | — |   |
| Investments in utility money pool arrangement                                 |   |               | (831,000   | ) |   |   | (274,200 | ) |   |   | (439,500 | ) |
| Repayments from utility money pool arrangement                                |   |               | 831,000    |   |   |   | 274,200 |   |   |   | 540,100 |   |
| Other investments                                                             |   |               | —    |   |   |   | — |   |   |   | 23,716 |   |
| Net cash used in investing activities                                         |   |               | (1,292,871 | ) |   |   | (586,303 | ) |   |   | (649,264 | ) |
|                                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Financing activities                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Proceeds from (repayment of) short-term borrowings — net                |   |               | 174,400    |   |   |   | 55,000 |   |   |   | (231,007 | ) |
| Proceeds from issuance of long-term debt                                      |   |               | 395,313    |   |   |   | 394,570 |   |   |   | 592,389 |   |
| Repayment of long-term debt, including reacquisition premiums                 |   |               | —    |   |   |   | (200,000 | ) |   |   | (301,445 | ) |
| Borrowings under utility money pool arrangement                               |   |               | 255,500    |   |   |   | 802,800 |   |   |   | 755,600 |   |
| Repayments under utility money pool arrangement                               |   |               | (339,500   | ) |   |   | (759,800 | ) |   |   | (714,600 | ) |
| Capital contributions from parent                                             |   |               | 260,116    |   |   |   | 108,813 |   |   |   | 127,529 |   |
| Dividends paid to parent                                                      |   |               | (265,806   | ) |   |   | (266,188 | ) |   |   | (270,966 | ) |
| Net cash provided by (used in) financing activities                           |   |               | 480,023    |   |   |   | 135,195 |   |   |   | (42,500 | ) |
|                                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Net increase (decrease) in cash and cash equivalents                          |   |               | (517       | ) |   |   | 22,231 |   |   |   | 3,548 |   |
| Cash and cash equivalents at beginning of period                              |   |               | 33,429     |   |   |   | 11,198 |   |   |   | 7,650 |   |
| Cash and cash equivalents at end of period                                    |   | $                  | 32,912     |   |   | $ | 33,429 |   |   | $ | 11,198 |   |
|                                                                          |   |               |       |   |   |   |   |   |   |   |   |   |
| Supplemental disclosure of cash flow information:                             |   |               |       |   |   |   |   |   |   |   |   |   |
| Cash paid for interest (net of amounts capitalized)                           |   | $                  | (156,906   | ) |   | $ | (147,186 | ) |   | $ | (131,098 | ) |
| Cash paid for income taxes, net                                               |   |               | (63,999    | ) |   |   | (6,155 | ) |   |   | (90,187 | ) |
| Supplemental disclosure of non-cash investing and financing transactions:     |   |               |       |   |   |   |   |   |   |   |   |   |
| Property, plant and equipment additions in accounts payable                   |   | $                  | 96,359     |   |   | $ | 13,332 |   |   | $ | 16,379 |   |
| Storage assets under capital lease                                            |   |               | 12,628     |   |   |   | 143,105 |   |   |   | — |   |

----

Index

|                                                                                  |   | Dec. 31, |       |
|---------------------------------------------------------------------------------------|--------|----------|------------|
|                                                                                  |   | 2010     |       |   | 2009 |   |
| Assets                                                                                |   |     |       |   |   |   |
| Current assets                                                                        |   |     |       |   |   |   |
| Cash and cash equivalents                                                             |   | $        | 32,912     |   |   | $ | 33,429 |   |
| Accounts receivable, net                                                              |   |     | 305,469    |   |   |   | 330,279 |   |
| Accounts receivable from affiliates                                                   |   |     | 21,042     |   |   |   | 33,396 |   |
| Accrued unbilled revenues                                                             |   |     | 297,535    |   |   |   | 313,953 |   |
| Regulatory assets                                                                     |   |     | 176,596    |   |   |   | 122,161 |   |
| Inventories                                                                           |   |     | 223,058    |   |   |   | 253,648 |   |
| Deferred income taxes                                                                 |   |     | 13,877     |   |   |   | 56,223 |   |
| Derivative instruments                                                                |   |     | 6,294      |   |   |   | 28,704 |   |
| Prepayments and other                                                                 |   |     | 54,235     |   |   |   | 58,968 |   |
| Total current assets                                                                  |   |     | 1,131,018  |   |   |   | 1,230,761 |   |
|                                                                                  |   |     |       |   |   |   |   |   |
| Property, plant and equipment, net                                                    |   |     | 9,200,556  |   |   |   | 8,104,841 |   |
|                                                                                  |   |     |       |   |   |   |   |   |
| Other assets                                                                          |   |     |       |   |   |   |   |   |
| Regulatory assets                                                                     |   |     | 824,205    |   |   |   | 730,307 |   |
| Derivative instruments                                                                |   |     | 18,035     |   |   |   | 104,664 |   |
| Other                                                                                 |   |     | 55,016     |   |   |   | 47,175 |   |
| Total other assets                                                                    |   |     | 897,256    |   |   |   | 882,146 |   |
| Total assets                                                                          |   | $        | 11,228,830 |   |   | $ | 10,217,748 |   |
|                                                                                  |   |     |       |   |   |   |   |   |
| Liabilities and Equity                                                                |   |     |       |   |   |   |   |   |
| Current liabilities                                                                   |   |     |       |   |   |   |   |   |
| Current portion of long-term debt                                                     |   | $        | 6,970      |   |   | $ | 3,964 |   |
| Short-term debt                                                                       |   |     | 269,400    |   |   |   | 95,000 |   |
| Borrowings under utility money pool arrangement                                       |   |     | —    |   |   |   | 84,000 |   |
| Accounts payable                                                                      |   |     | 382,380    |   |   |   | 422,276 |   |
| Accounts payable to affiliates                                                        |   |     | 28,270     |   |   |   | 40,758 |   |
| Regulatory liabilities                                                                |   |     | 50,018     |   |   |   | 80,464 |   |
| Taxes accrued                                                                         |   |     | 94,321     |   |   |   | 80,303 |   |
| Dividends payable to parent                                                           |   |     | 66,828     |   |   |   | 65,822 |   |
| Derivative instruments                                                                |   |     | 29,047     |   |   |   | 18,285 |   |
| Accrued interest                                                                      |   |     | 48,866     |   |   |   | 47,300 |   |
| Other                                                                                 |   |     | 100,984    |   |   |   | 67,692 |   |
| Total current liabilities                                                             |   |     | 1,077,084  |   |   |   | 1,005,864 |   |
|                                                                                  |   |     |       |   |   |   |   |   |
| Deferred credits and other liabilities                                                |   |     |       |   |   |   |   |   |
| Deferred income taxes                                                                 |   |     | 1,539,583  |   |   |   | 1,421,386 |   |
| Deferred investment tax credits                                                       |   |     | 47,338     |   |   |   | 50,031 |   |
| Regulatory liabilities                                                                |   |     | 472,846    |   |   |   | 494,579 |   |
| Pension and employee benefit obligations                                              |   |     | 303,946    |   |   |   | 257,881 |   |
| Customer advances                                                                     |   |     | 244,345    |   |   |   | 271,171 |   |
| Derivative instruments                                                                |   |     | 43,220     |   |   |   | 49,587 |   |
| Asset retirement obligations                                                          |   |     | 72,687     |   |   |   | 65,160 |   |
| Other                                                                                 |   |     | 61,334     |   |   |   | 31,287 |   |
| Total deferred credits and other liabilities                                          |   |     | 2,785,299  |   |   |   | 2,641,082 |   |
|                                                                                  |   |     |       |   |   |   |   |   |
| Commitments and contingent liabilities                                                |   |     |       |   |   |   |   |   |
| Capitalization                                                                        |   |     |       |   |   |   |   |   |
| Long-term debt                                                                        |   |     | 3,228,253  |   |   |   | 2,824,988 |   |
| Common stock – authorized 100 shares of $0.01 par value; outstanding 100 shares |   |     | —    |   |   |   | — |   |
| Additional paid-in capital                                                            |   |     | 3,255,586  |   |   |   | 2,995,470 |   |
| Retained earnings                                                                     |   |     | 875,151    |   |   |   | 742,243 |   |
| Accumulated other comprehensive income                                                |   |     | 7,457      |   |   |   | 8,101 |   |
| Total common stockholder’s equity                                               |   |     | 4,138,194  |   |   |   | 3,745,814 |   |
| Total liabilities and equity                                                          |   | $        | 11,228,830 |   |   | $ | 10,217,748 |   |

----

Index

|                                                                                                  |   | Common Stock Issued |   |   |      |   |    | Accumulated |   |   | Total     |   |
|-------------------------------------------------------------------------------------------------------|--------|---------------------|--------|--------|-----------|--------|---------|-------------|--------|--------|-----------|--------|
|                                                                                                  |   |                |   |   |      |   |    | Additional  |   |   |      |   |   | Other |   |   | Common |   |
|                                                                                                  |   |                |   |   |      |   |    | Paid In     |   |   | Retained  |   |   | Comprehensive |   |   | Stockholders’ |   |
|                                                                                                  |   | Shares              |   |   | Par Value |   |    | Capital     |   |   | Earnings  |   |   | Income (Loss) |   |   | Equity |   |
| Balance at Dec. 31, 2007                                                                              |   |                | 100    |   |      | $      | — |        |   | $      | 2,759,128 |   |   | $ | 614,267 |   |   | $ | 12,447 |   |   | $ | 3,385,842 |   |
| Adoption of new accounting guidance for endorsement split-dollar life insurance, net of tax of $(391) |   |                |   |   |      |   |    |        |   |   |      |   |   |   | (617 | ) |   |   |   |   |   |   | (617 | ) |
| Net income                                                                                            |   |                |   |   |      |   |    |        |   |   |      |   |   |   | 339,796 |   |   |   |   |   |   |   | 339,796 |   |
| Net derivative instrument fair value changes during the period, net of tax of $(2,910)                |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   | (4,819 | ) |   |   | (4,819 | ) |
| Comprehensive income for 2008                                                                         |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   |   |   |   |   | 334,977 |   |
| Common dividends declared to parent                                                                   |   |                |   |   |      |   |    |        |   |   |      |   |   |   | (269,930 | ) |   |   |   |   |   |   | (269,930 | ) |
| Contribution of capital by parent                                                                     |   |                |   |   |      |   |    |        |   |   | 127,529   |   |   |   |   |   |   |   |   |   |   |   | 127,529 |   |
| Balance at Dec. 31, 2008                                                                              |   |                | 100    |   |      | $      | — |        |   | $      | 2,886,657 |   |   | $ | 683,516 |   |   | $ | 7,628 |   |   | $ | 3,577,801 |   |
| Net income                                                                                            |   |                |   |   |      |   |    |        |   |   |      |   |   |   | 323,320 |   |   |   |   |   |   |   | 323,320 |   |
| Net derivative instrument fair value changes during the period, net of tax of $298                    |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   | 473 |   |   |   | 473 |   |
| Comprehensive income for 2009                                                                         |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   |   |   |   |   | 323,793 |   |
| Common dividends declared to parent                                                                   |   |                |   |   |      |   |    |        |   |   |      |   |   |   | (264,593 | ) |   |   |   |   |   |   | (264,593 | ) |
| Contribution of capital by parent                                                                     |   |                |   |   |      |   |    |        |   |   | 108,813   |   |   |   |   |   |   |   |   |   |   |   | 108,813 |   |
| Balance at Dec. 31, 2009                                                                              |   |                | 100    |   |      | $      | — |        |   | $      | 2,995,470 |   |   | $ | 742,243 |   |   | $ | 8,101 |   |   | $ | 3,745,814 |   |
| Net income                                                                                            |   |                |   |   |      |   |    |        |   |   |      |   |   |   | 399,720 |   |   |   |   |   |   |   | 399,720 |   |
| Net derivative instrument fair value changes during the period, net of tax of $(394)                  |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   | (644 | ) |   |   | (644 | ) |
| Comprehensive income for 2010                                                                         |   |                |   |   |      |   |    |        |   |   |      |   |   |   |   |   |   |   |   |   |   |   | 399,076 |   |
| Common dividends declared to parent                                                                   |   |                |   |   |      |   |    |        |   |   |      |   |   |   | (266,812 | ) |   |   |   |   |   |   | (266,812 | ) |
| Contribution of capital by parent                                                                     |   |                |   |   |      |   |    |        |   |   | 260,116   |   |   |   |   |   |   |   |   |   |   |   | 260,116 |   |
| Balance at Dec. 31, 2010                                                                              |   |                | 100    |   |      | $      | — |        |   | $      | 3,255,586 |   |   | $ | 875,151 |   |   | $ | 7,457 |   |   | $ | 4,138,194 |   |

----

Index

|                                                                                                   |   | Dec. 31 |      |
|--------------------------------------------------------------------------------------------------------|--------|---------|-----------|
|                                                                                                   |   | 2010    |      |   | 2009 |   |
| Long-Term Debt                                                                                         |   |    |      |   |   |   |
| First Mortgage Bonds, Series due:                                                                      |   |    |      |   |   |   |
| Oct. 1, 2012, 7.875%                                                                                   |   | $       | 600,000   |   |   | $ | 600,000 |   |
| March 1, 2013, 4.875%                                                                                  |   |    | 250,000   |   |   |   | 250,000 |   |
| April 1, 2014, 5.5%                                                                                    |   |    | 275,000   |   |   |   | 275,000 |   |
| Sept. 1, 2017, 4.375% (a)                                                                              |   |    | 129,500   |   |   |   | 129,500 |   |
| Aug. 1, 2018, 5.8%                                                                                     |   |    | 300,000   |   |   |   | 300,000 |   |
| Jan. 1, 2019, 5.1% (a)                                                                                 |   |    | 48,750    |   |   |   | 48,750 |   |
| June 1, 2019, 5.125%                                                                                   |   |    | 400,000   |   |   |   | 400,000 |   |
| Nov. 15, 2020, 3.2%                                                                                    |   |    | 400,000   |   |   |   | — |   |
| Sept. 1, 2037, 6.25%                                                                                   |   |    | 350,000   |   |   |   | 350,000 |   |
| Aug. 1, 2038, 6.5%                                                                                     |   |    | 300,000   |   |   |   | 300,000 |   |
| Capital lease obligations, through 2060, 11.2% — 13.6%                                           |   |    | 190,223   |   |   |   | 183,026 |   |
| Unamortized debt                                                                                       |   |    | (8,250    | ) |   |   | (7,324 | ) |
| Total                                                                                                  |   |    | 3,235,223 |   |   |   | 2,828,952 |   |
| Less current maturities                                                                                |   |    | 6,970     |   |   |   | 3,964 |   |
| Total long-term debt                                                                                   |   | $       | 3,228,253 |   |   | $ | 2,824,988 |   |
|                                                                                                   |   |    |      |   |   |   |   |   |
| Common Stockholder’s Equity                                                                      |   |    |      |   |   |   |   |   |
| Common stock — authorized 100 shares of $0.01 par value; outstanding 100 shares in 2010 and 2009 |   | $       | —   |   |   | $ | — |   |
| Additional paid-in capital                                                                             |   |    | 3,255,586 |   |   |   | 2,995,470 |   |
| Retained earnings                                                                                      |   |    | 875,151   |   |   |   | 742,243 |   |
| Accumulated comprehensive income                                                                       |   |    | 7,457     |   |   |   | 8,101 |   |
| Total common stockholder’s equity                                                                |   | $       | 4,138,194 |   |   | $ | 3,745,814 |   |

----

Index

| ● | PSCo generally recovers all prudently incurred electric fuel and purchased energy costs through the ECA for PSCo’s retail jurisdiction.  The ECA allows for sharing of margins on short term energy sales and margins from the sale of SO2 allowances. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PSCo generally recovers all purchased capacity costs through the PCCA for the company’s retail jurisdiction.  The PCCA mechanism is revised annually.  In October 2010, the CPUC approved the acquisition of generation assets from subsidiaries of Calpine Corporation and the associated cost recovery of the purchase through the PCCA mechanism on an interim basis until PSCo’s next electric rate case on or before April 30, 2012. |
|---------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PSCo’s rates include annual adjustments for the recovery of conservation and energy management program costs, as well as a financial incentive based on its performance in achieving established goals through the DSMCA.  PSCo is allowed to recover certain costs associated with renewable energy resources through a specific retail rate rider.  PSCo recovers costs associated with investment in transmission facilities made after December 2008 through the TCA rate rider. |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PSCo sells firm power and energy in wholesale markets, which are regulated by the FERC.  Certain of these rates include monthly wholesale fuel cost-recovery mechanisms. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

----

Index

----

Index

| ● | Certain costs, which would otherwise be charged to expense, are deferred as regulatory assets based on the expected ability to recover the costs in future rates; and |
|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | Certain credits, which would otherwise be reflected as income, are deferred as regulatory liabilities based on the expectation the amounts will be returned to customers in future rates, or because the amounts were collected in rates prior to the costs being incurred. |
|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

----

Index

| 2. | Accounting Pronouncements |
|----|---------------------------|

| 3. | Selected Balance Sheet Data |
|----|-----------------------------|

| (Thousands of Dollars)              |   | Dec. 31, 2010 |       |   | Dec. 31, 2009 |   |
|-------------------------------------|--------|---------------|------------|--------|---------------|--------|
| Accounts receivable, net            |   |          |       |   |          |   |
| Accounts receivable                 |   | $             | 329,523    |   |          | $      | 354,428 |   |
| Less allowance for bad debts        |   |          | (24,054    | )      |          |   | (24,149 | ) |
|                                |   | $             | 305,469    |   |          | $      | 330,279 |   |
| Inventories                         |   |          |       |   |          |   |   |   |
| Materials and supplies              |   | $             | 51,615     |   |          | $      | 45,809 |   |
| Fuel                                |   |          | 67,187     |   |          |   | 96,964 |   |
| Natural gas                         |   |          | 104,256    |   |          |   | 110,875 |   |
|                                |   | $             | 223,058    |   |          | $      | 253,648 |   |
| Property, plant and equipment, net  |   |          |       |   |          |   |   |   |
| Electric plant                      |   | $             | 9,003,103  |   |          | $      | 7,448,911 |   |
| Natural gas plant                   |   |          | 2,284,212  |   |          |   | 2,133,116 |   |
| Common and other property           |   |          | 757,059    |   |          |   | 731,511 |   |
| Plant to be retired (a)             |   |          | 236,606    |   |          |   | 48,572 |   |
| Construction work in progress       |   |          | 231,636    |   |          |   | 1,038,013 |   |
| Total property, plant and equipment |   |          | 12,512,616 |   |          |   | 11,400,123 |   |
| Less accumulated depreciation       |   |          | (3,312,060 | )      |          |   | (3,295,282 | ) |
|                                |   | $             | 9,200,556  |   |          | $      | 8,104,841 |   |

| (a) |   In 2009, in accordance with the CPUC’s approval of PSCo’s 2007 Colorado resource plan and subsequent rate case decisions, PSCo agreed to early retire its Cameo Units 1 and 2, Arapahoe Units 3 and 4 and Zuni Units 1 and 2 facilities.  In 2010, in response to the CACJA, the CPUC approved the early retirement of Cherokee Units 1, 2 and 3, Arapahoe Unit 3 and Valmont Unit 5 between 2011 and 2017.  Amounts are presented net of accumulated depreciation.  See Item 1 – Public Utility Regulation for further discussion. |
|-----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

| (Millions of Dollars)          |   | Dec. 31, 2010 |    |   | Dec. 31, 2009 |   |
|--------------------------------|--------|---------------|---------|--------|---------------|--------|
| Money pool borrowings          |   | $             | — |   |          | $      | 84 |   |
| Weighted average interest rate |   |          | N/A     |   |          |   | 0.36 | % |
| Money pool borrowing limit     |   | $             | 250     |   |          | $      | 250 |   |

| (Millions of Dollars)            |   | Dec. 31, 2010 |   |   | Dec. 31, 2009 |   |
|----------------------------------|--------|---------------|--------|--------|---------------|--------|
| Commercial paper outstanding     |   | $             | 269    |   |          | $      | 95 |   |
| Weighted average interest rate   |   |          | 0.42   |   |          |   | 0.35 | % |
| Commercial paper borrowing limit |   | $             | 675    |   |          | $      | 675 |   |

| Credit   |   |   |   |   |   |      |   |   |          |   |   |      |   |
|----------|--------|--------|--------|--------|--------|-----------|--------|--------|---------------|--------|--------|-----------|--------|
| Facility |   |   | Drawn* |   |   | Available |   |   | Original Term |   |   | Maturity  |   |
| $        | 675    |   |   | $      | 275    |      |   | $      | 400           |   |   | Five year |   |   | December 2011 |   |

| ● | The credit facility has one financial covenant requiring that PSCo’s debt-to-total capitalization ratio be less than or equal to 65 percent.  PSCo was in compliance as its debt-to-total capitalization ratio was 46 percent and 45 percent at Dec. 31, 2010 and 2009, respectively.  If PSCo does not comply with the covenant, an event of default may be declared and it not remedied, and any outstanding amounts due under the facility can be declared due by the lender. |
|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | The credit facility has a cross default provision that provides Xcel Energy will be in default on its borrowings under the facility if any of its subsidiaries, comprising more than 15 percent of the consolidated assets of Xcel Energy on a consolidated basis, defaults on any of its indebtedness greater than $50 million. |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | The interest rate is based on either the agent bank’s prime rate or the applicable LIBOR, plus a borrowing margin as based on PSCo’s applicable debt ratings; this is 25 points. |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | The commitment fees, also based on long-term credit ratings, are calculated for the unused portion of the credit facility at 6 basis points for PSCo. |
|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | At Dec. 31, 2010, PSCo had no direct borrowings on this line of credit; however, the credit facility was used to provide back-up support for $269.4 million of commercial paper outstanding and $4.7 million of letters of credit.  At Dec. 31, 2009, PSCo had no direct borrowings on this line of credit; however, the credit facility was used to provide back-up support for $95.0 million of commercial paper outstanding and $4.6 million of letters of credit. |
|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | Xcel Energy plans to syndicate new credit agreements at the Holding Company, NSP-Minnesota, PSCo, SPS and NSP-Wisconsin during the first quarter of 2011 to replace the existing agreements.  The total anticipated size of the new credit facilities will be approximately $2.45 billion, of which $700 million is related to PSCo. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

| (Millions of Dollars) |   |   |    |
|-----------------------|--------|--------|---------|
| 2011                  |   | $      | 7       |   |
| 2012                  |   |   | 606     |   |
| 2013                  |   |   | 257     |   |
| 2014                  |   |   | 282     |   |
| 2015                  |   |   |  6 |   |

| Preferred  |   |   |      |   |   | Preferred   |
|------------|--------|--------|-----------|--------|--------|-------------|
| Shares     |   |   |      |   |   | Shares      |
| Authorized |   |   | Par Value |   |   | Outstanding |
| 10,000,000 |   |   | $         | 0.01   |   |        | None |

|                                                     |   |     |      |   |         |   |    | Construction |   |   |        |   |
|----------------------------------------------------------|--------|----------|-----------|--------|--------------|--------|---------|--------------|--------|--------|-------------|--------|
|                                                     |   | Plant in |      |   | Accumulated  |   |    | Work in      |   |   |        |   |
| (Thousands of Dollars)                                   |   | Service  |      |   | Depreciation |   |    | Progress     |   |   | Ownership % |   |
| Electric Generation:                                     |   |     |      |   |         |   |    |         |   |   |        |   |
| Hayden Unit 1                                            |   | $        | 89,176    |   |         | $      | 59,191  |         |   | $      | —     |   |   |   | 75.5 |   |
| Hayden Unit 2                                            |   |     | 82,079    |   |         |   | 54,680  |         |   |   | 21,405      |   |   |   | 37.4 |   |
| Hayden Common Facilities                                 |   |     | 33,553    |   |         |   | 13,286  |         |   |   | 170         |   |   |   | 53.1 |   |
| Craig Units 1 and 2                                      |   |     | 53,878    |   |         |   | 32,344  |         |   |   | 284         |   |   |   | 9.7 |   |
| Craig Common Facilities 1, 2 and 3                       |   |     | 33,710    |   |         |   | 15,444  |         |   |   | 2,534       |   |   |   | 6.5 - 9.7 |   |
| Comanche Unit 3                                          |   |     | 882,626   |   |         |   | 11,069  |         |   |   | 130         |   |   |   | 66.7 |   |
| Comanche Common Facilities                               |   |     | 4,246     |   |         |   | 80      |         |   |   | 3,205       |   |   |   | 82.0 |   |
| Electric Transmission:                                   |   |     |      |   |         |   |    |         |   |   |        |   |   |   |   |   |
| Transmission and other facilities, including substations |   |     | 148,002   |   |         |   | 55,249  |         |   |   | 2,080       |   |   | Various |   |
| Gas Transportation:                                      |   |     |      |   |         |   |    |         |   |   |        |   |   |   |   |   |
| Rifle to Avon                                            |   |     | 16,278    |   |         |   | 6,369   |         |   |   | 4           |   |   |   | 60.0 |   |
| Total                                                    |   | $        | 1,343,548 |   |         | $      | 247,712 |         |   | $      | 29,812      |   |   |   |   |   |

----

Index

----

Index

| (Millions of Dollars)                              |   | Dec. 31, 2010 |   |   | Dec. 31, 2009 |   |
|----------------------------------------------------|--------|---------------|--------|--------|---------------|--------|
| Unrecognized tax benefit - Permanent tax positions |   | $             | 1.3    |   |          | $      | 1.0 |   |
| Unrecognized tax benefit - Temporary tax positions |   |          | 10.3   |   |          |   | 6.2 |   |
| Unrecognized tax benefit balance                   |   | $             | 11.6   |   |          | $      | 7.2 |   |

| (Millions of Dollars)                                         |   | 2010   |    |   | 2009   |   |    | 2008   |   |
|---------------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| Balance at Jan. 1                                             |   | $      | 7.2     |   |   | $      | 10.3    |   |   | $ | 8.8 |   |
| Additions based on tax positions related to the current year  |   |   | 4.1     |   |   |   | 3.7     |   |   |   | 2.9 |   |
| Reductions based on tax positions related to the current year |   |   | (0.2    | )      |   |   | (0.3    | )      |   |   | (0.5 | ) |
| Additions for tax positions of prior years                    |   |   | 1.6     |   |   |   | 2.2     |   |   |   | 2.0 |   |
| Reductions for tax positions of prior years                   |   |   | (1.1    | )      |   |   | (0.5    | )      |   |   | (0.2 | ) |
| Settlements with taxing authorities                           |   |   | — |   |   |   | (8.2    | )      |   |   | — |   |
| Lapse of applicable statutes of limitations                   |   |   | — |   |   |   | — |   |   |   | (2.7 | ) |
| Balance at Dec. 31                                            |   | $      | 11.6    |   |   | $      | 7.2     |   |   | $ | 10.3 |   |

| (Millions of Dollars)            |   | Dec. 31, 2010 |   |   | Dec. 31, 2009 |   |
|----------------------------------|--------|---------------|--------|--------|---------------|--------|
| NOL and tax credit carryforwards |   | $             | (7.2   | )      |          | $      | (4.0 | ) |

| (Millions of Dollars)                                                |   | 2010   |    |   | 2009   |   |   | 2008   |   |
|----------------------------------------------------------------------|--------|--------|---------|--------|--------|--------|--------|--------|--------|
| Payable for interest related to unrecognized tax benefits at Jan. 1  |   | $      | (0.1    | )      |   | $      | (0.4   | )      |   | $ | (3.8 | ) |
| Interest income related to unrecognized tax benefits                 |   |   | — |   |   |   | 0.3    |   |   |   | 3.4 |   |
| Payable for interest related to unrecognized tax benefits at Dec. 31 |   | $      | (0.1    | )      |   | $      | (0.1   | )      |   | $ | (0.4 | ) |

| (Millions of Dollars)                                    |   | 2010   |   |   | 2009   |   |
|----------------------------------------------------------|--------|--------|--------|--------|--------|--------|
| Federal NOL carryforward                                 |   | $      | 150.5  |   |   | $      | 158.8 |   |
| Federal tax credit carryforwards                         |   |   | 14.6   |   |   |   | 13.6 |   |
| State NOL carryforward                                   |   |   | 298.2  |   |   |   | 97.5 |   |
| State tax credit carryforwards, net of federal detriment |   |   | 8.4    |   |   |   | 7.1 |   |

----

Index

|                                                      |   | 2010   |    |   | 2009   |   |    | 2008   |   |
|-----------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| Federal statutory rate                                    |   |   | 35.0    | %      |   |   | 35.0    | %      |   |   | 35.0 | % |
| Increases (decreases) in tax from:                        |   |   |    |   |   |   |    |   |   |   |   |   |
| State income taxes, net of federal income tax benefit     |   |   | 1.1     |   |   |   | 3.3     |   |   |   | 1.7 |   |
| Regulatory differences — utility plant items        |   |   | (0.5    | )      |   |   | (2.7    | )      |   |   | (2.2 | ) |
| Life insurance policies                                   |   |   | (1.4    | )      |   |   | — |   |   |   | (0.2 | ) |
| Tax credits recognized, net of federal income tax expense |   |   | (0.8    | )      |   |   | (1.0    | )      |   |   | (1.1 | ) |
| Resolution of income tax audits and other                 |   |   | 1.2     |   |   |   | 0.1     |   |   |   | 0.3 |   |
| Change in unrecognized tax benefits                       |   |   | — |   |   |   | (0.1    | )      |   |   | (0.3 | ) |
| Previously recognized Medicare Part D subsidies           |   |   | 1.6     |   |   |   | — |   |   |   | — |   |
| Other, net                                                |   |   | 0.2     |   |   |   | (0.1    | )      |   |   | (0.3 | ) |
| Effective income tax rate                                 |   |   | 36.4    | %      |   |   | 34.5    | %      |   |   | 32.9 | % |

| (Thousands of Dollars)                                |   | 2010   |    |   | 2009   |   |    | 2008   |   |
|-------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| Current federal tax expense (benefit)                 |   | $      | 76,228  |   |   | $      | (20,867 | )      |   | $ | 77,865 |   |
| Current state tax expense (benefit)                   |   |   | (461    | )      |   |   | (2,327  | )      |   |   | 6,219 |   |
| Current change in unrecognized tax expense (benefit)  |   |   | 1,246   |   |   |   | (1,374  | )      |   |   | (571 | ) |
| Deferred federal tax expense                          |   |   | 147,704 |   |   |   | 172,454 |   |   |   | 81,326 |   |
| Deferred state tax expense                            |   |   | 11,180  |   |   |   | 27,508  |   |   |   | 8,859 |   |
| Deferred change in unrecognized tax expense (benefit) |   |   | (920    | )      |   |   | 864     |   |   |   | (841 | ) |
| Deferred tax credits                                  |   |   | (3,103  | )      |   |   | (3,478  | )      |   |   | (3,469 | ) |
| Deferred investment tax credits                       |   |   | (2,693  | )      |   |   | (2,375  | )      |   |   | (2,760 | ) |
| Total income tax expense                              |   | $      | 229,181 |   |   | $      | 170,405 |   |   | $ | 166,628 |   |

| (Thousands of Dollars)                                                                               |   | 2010   |    |   | 2009   |   |    | 2008   |   |
|------------------------------------------------------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| Deferred tax expense excluding items below                                                           |   | $      | 160,543 |   |   | $      | 224,484 |   |   | $ | 109,504 |   |
| Amortization and adjustments to deferred income taxes onincome tax regulatory assets and liabilities |   |   | (6,075  | )      |   |   | (26,838 | )      |   |   | (26,540 | ) |
| Tax expense (benefit) allocated to other comprehensive income and other                              |   |   | 393     |   |   |   | (298    | )      |   |   | 2,911 |   |
| Deferred tax expense                                                                                 |   | $      | 154,861 |   |   | $      | 197,348 |   |   | $ | 85,875 |   |

| (Thousands of Dollars)                            |   | 2010   |      |   | 2009   |   |
|---------------------------------------------------|--------|--------|-----------|--------|--------|--------|
| Deferred tax liabilities:                         |   |   |      |   |   |   |
| Difference between book and tax bases of property |   | $      | 1,527,296 |   |   | $      | 1,352,421 |   |
| Employee benefits                                 |   |   | 105,578   |   |   |   | 98,835 |   |
| Other                                             |   |   | 122,856   |   |   |   | 123,676 |   |
| Total deferred tax liabilities                    |   | $      | 1,755,730 |   |   | $      | 1,574,932 |   |

----

Index

| (Thousands of Dollars)          |   | 2010   |      |   | 2009   |   |
|---------------------------------|--------|--------|-----------|--------|--------|--------|
| Deferred tax assets:            |   |   |      |   |   |   |
| NOL carryforward                |   | $      | 73,948    |   |   | $      | 67,749 |   |
| Unbilled revenue - fuel costs   |   |   | 59,182    |   |   |   | 59,318 |   |
| Tax credit carryforward         |   |   | 22,983    |   |   |   | 20,737 |   |
| Regulatory liabilities          |   |   | 18,249    |   |   |   | 20,371 |   |
| Deferred investment tax credits |   |   | 17,989    |   |   |   | 19,011 |   |
| Litigation reserve              |   |   | 11,433    |   |   |   | 68 |   |
| Other                           |   |   | 26,240    |   |   |   | 22,514 |   |
| Total deferred tax assets       |   |   | 230,024   |   |   |   | 209,768 |   |
| Net deferred tax liability      |   | $      | 1,525,706 |   |   | $      | 1,365,164 |   |

----

Index

|                                               |   | 2010   |   |   | 2009   |   |
|----------------------------------------------------|--------|--------|--------|--------|--------|--------|
| Domestic and international equity securities       |   |   | 24     | %      |   |   | 24 | % |
| Long-duration fixed income securities              |   |   | 41     |   |   |   | 34 |   |
| Short-to-intermediate term fixed income securities |   |   | 11     |   |   |   | 19 |   |
| Alternative investments                            |   |   | 17     |   |   |   | 18 |   |
| Cash                                               |   |   | 7      |   |   |   | 5 |   |
| Total                                              |   |   | 100    | %      |   |   | 100 | % |

|                                               |   | Dec. 31, 2010 |    |
|----------------------------------------------------|--------|---------------|---------|
|                                               |   |          |    |   |   |   |   |   |   |   |   |   |
| (Thousands of Dollars)                             |   | Level 1       |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |
| Cash equivalents                                   |   | $             | — |   |   | $ | 109,027 |   |   | $ | — |   |   | $ | 109,027 |   |
| Short-term investments                             |   |          | 122,643 |   |   |   | 26,683 |   |   |   | — |   |   |   | 149,326 |   |
| Derivatives                                        |   |          | — |   |   |   | 8,140 |   |   |   | — |   |   |   | 8,140 |   |
| Government securities                              |   |          | — |   |   |   | 117,522 |   |   |   | — |   |   |   | 117,522 |   |
| Corporate bonds                                    |   |          | — |   |   |   | 641,807 |   |   |   | — |   |   |   | 641,807 |   |
| Asset-backed securities                            |   |          | — |   |   |   | — |   |   |   | 26,986 |   |   |   | 26,986 |   |
| Mortgage-backed securities                         |   |          | — |   |   |   | — |   |   |   | 113,418 |   |   |   | 113,418 |   |
| Common stock                                       |   |          | 117,899 |   |   |   | — |   |   |   | — |   |   |   | 117,899 |   |
| Private equity investments                         |   |          | — |   |   |   | — |   |   |   | 122,223 |   |   |   | 122,223 |   |
| Commingled equity and bond funds                   |   |          | — |   |   |   | 1,152,386 |   |   |   | — |   |   |   | 1,152,386 |   |
| Real estate                                        |   |          | — |   |   |   | — |   |   |   | 73,701 |   |   |   | 73,701 |   |
| Securities lending collateral obligation and other |   |          | — |   |   |   | (91,727 | ) |   |   | — |   |   |   | (91,727 | ) |
| Total                                              |   | $             | 240,542 |   |   | $ | 1,963,838 |   |   | $ | 336,328 |   |   | $ | 2,540,708 |   |

----

Index

|                                               |   | Dec. 31, 2009 |    |
|----------------------------------------------------|--------|---------------|---------|
|                                               |   |          |    |   |   |   |   |   |   |   |   |   |
| (Thousands of Dollars)                             |   | Level 1       |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |
| Cash equivalents                                   |   | $             | — |   |   | $ | 221,971 |   |   | $ | — |   |   | $ | 221,971 |   |
| Short-term investments                             |   |          | — |   |   |   | 324,683 |   |   |   | — |   |   |   | 324,683 |   |
| Derivatives                                        |   |          | — |   |   |   | 11,606 |   |   |   | — |   |   |   | 11,606 |   |
| Government securities                              |   |          | — |   |   |   | 94,949 |   |   |   | — |   |   |   | 94,949 |   |
| Corporate bonds                                    |   |          | — |   |   |   | 522,403 |   |   |   | — |   |   |   | 522,403 |   |
| Asset-backed securities                            |   |          | — |   |   |   | — |   |   |   | 47,825 |   |   |   | 50,232 |   |
| Mortgage-backed securities                         |   |          | — |   |   |   | — |   |   |   | 144,006 |   |   |   | 141,599 |   |
| Common stock                                       |   |          | 89,260  |   |   |   | — |   |   |   | — |   |   |   | 89,260 |   |
| Private equity investments                         |   |          | — |   |   |   | — |   |   |   | 82,098 |   |   |   | 82,098 |   |
| Commingled equity and bond funds                   |   |          | — |   |   |   | 1,014,072 |   |   |   | — |   |   |   | 1,014,072 |   |
| Real estate                                        |   |          | — |   |   |   | — |   |   |   | 66,704 |   |   |   | 66,704 |   |
| Securities lending collateral obligation and other |   |          | — |   |   |   | (170,251 | ) |   |   | — |   |   |   | (170,251 | ) |
| Total                                              |   | $             | 89,260  |   |   | $ | 2,019,433 |   |   | $ | 340,633 |   |   | $ | 2,449,326 |   |

|                       |   |         |    |   |           |   |    |             |   |   |          |   |
|----------------------------|--------|--------------|---------|--------|----------------|--------|---------|------------------|--------|--------|---------------|--------|
|                       |   |         |    |   | Realized and   |   |    | Purchases,       |   |   |          |   |
|                       |   |         |    |   | Unrealized     |   |    | Issuances, and   |   |   |          |   |
| (Thousands of Dollars)     |   | Jan. 1, 2010 |    |   | Gains (Losses) |   |    | Settlements, net |   |   | Dec. 31, 2010 |   |
| Asset-backed securities    |   | $            | 47,825  |   |           | $      | (3,678  | )                |   | $      | (17,161       | )      |   | $ | 26,986 |   |
| Mortgage-backed securities |   |         | 144,006 |   |           |   | (5,376  | )                |   |   | (25,212       | )      |   |   | 113,418 |   |
| Real estate                |   |         | 66,704  |   |           |   | 7,100   |             |   |   | (103          | )      |   |   | 73,701 |   |
| Private equity investments |   |         | 82,098  |   |           |   | (1,032  | )                |   |   | 41,157        |   |   |   | 122,223 |   |
| Total                      |   | $            | 340,633 |   |           | $      | (2,986  | )                |   | $      | (1,319        | )      |   | $ | 336,328 |   |
|                       |   |         |    |   |           |   |    |             |   |   |          |   |   |   |   |   |
|                       |   |         |    |   | Realized and   |   |    | Purchases,       |   |   |          |   |   |
|                       |   |         |    |   | Unrealized     |   |    | Issuances, and   |   |   |          |   |   |
| (Thousands of Dollars)     |   | Jan. 1, 2009 |    |   | Gains (Losses) |   |    | Settlements, net |   |   | Dec. 31, 2009 |   |
| Asset-backed securities    |   | $            | 77,398  |   |           | $      | 48,285  |             |   | $      | (77,858       | )      |   | $ | 47,825 |   |
| Mortgage-backed securities |   |         | 166,610 |   |           |   | 103,470 |             |   |   | (126,074      | )      |   |   | 144,006 |   |
| Real estate                |   |         | 109,289 |   |           |   | (43,207 | )                |   |   | 622           |   |   |   | 66,704 |   |
| Private equity investments |   |         | 81,034  |   |           |   | (5,682  | )                |   |   | 6,746         |   |   |   | 82,098 |   |
| Total                      |   | $            | 434,331 |   |           | $      | 102,866 |             |   | $      | (196,564      | )      |   | $ | 340,633 |   |

|                                      |   |   |      |   |   |   |
|-------------------------------------------|--------|--------|-----------|--------|--------|--------|
| (Thousands of Dollars)                    |   | 2010   |      |   | 2009   |   |
| Accumulated Benefit Obligation at Dec. 31 |   | $      | 2,865,845 |   |   | $      | 2,676,174 |   |
|                                      |   |   |      |   |   |   |   |   |
| Change in Projected Benefit Obligation:   |   |   |      |   |   |   |   |   |
| Obligation at Jan. 1                      |   | $      | 2,829,631 |   |   | $      | 2,598,032 |   |
| Service cost                              |   |   | 73,147    |   |   |   | 65,461 |   |
| Interest cost                             |   |   | 165,010   |   |   |   | 169,790 |   |
| Plan amendments                           |   |   | 18,739    |   |   |   | (35,341 | ) |
| Actuarial loss                            |   |   | 169,203   |   |   |   | 223,122 |   |
| Benefit payments                          |   |   | (225,438  | )      |   |   | (191,433 | ) |
| Obligation at Dec. 31                     |   | $      | 3,030,292 |   |   | $      | 2,829,631 |   |

----

Index

| (Thousands of Dollars)                                                                                                 |   | 2010          |      |   | 2009          |   |
|------------------------------------------------------------------------------------------------------------------------|--------|---------------|-----------|--------|---------------|--------|
| Change in Fair Value of Plan Assets:                                                                                   |   |          |      |   |          |   |
| Fair value of plan assets at Jan. 1                                                                                    |   | $             | 2,449,326 |   |          | $      | 2,185,203 |   |
| Actual return on plan assets                                                                                           |   |          | 282,688   |   |          |   | 255,556 |   |
| Employer contributions                                                                                                 |   |          | 34,132    |   |          |   | 200,000 |   |
| Benefit payments                                                                                                       |   |          | (225,438  | )      |          |   | (191,433 | ) |
| Fair value of plan assets at Dec. 31                                                                                   |   | $             | 2,540,708 |   |          | $      | 2,449,326 |   |
| Funded Status of Plans at Dec. 31:                                                                                     |   |          |      |   |          |   |   |   |
| Funded status (a)                                                                                                      |   | $             | (489,584  | )      |          | $      | (380,305 | ) |
|                                                                                                                   |   |          |      |   |          |   |   |   |
| PSCo Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:                                            |   |          |      |   |          |   |   |   |
| Net loss                                                                                                               |   | $             | 464,143   |   |          | $      | 447,815 |   |
| Prior service credit                                                                                                   |   |          | (22,414   | )      |          |   | (22,221 | ) |
| Total                                                                                                                  |   | $             | 441,729   |   |          | $      | 425,594 |   |
| Amounts Related to the Funded Status of the Plans Have Been Recorded as Follows Based Upon Expected Recovery in Rates: |   |          |      |   |          |   |   |   |
| Regulatory assets                                                                                                      |   | $             | 441,729   |   |          | $      | 425,594 |   |
| PSCo accrued benefit liability recorded                                                                                |   |          | 122,336   |   |          |   | 90,989 |   |
| Measurement Date                                                                                                       |   | Dec. 31, 2010 |      |   | Dec. 31, 2009 |   |
| Significant Assumptions Used to Measure Benefit Obligations:                                                           |   |          |      |   |          |   |   |   |
| Discount rate for year-end valuation                                                                                   |   |          | 5.50      | %      |          |   | 6.00 | % |
| Expected average long-term increase in compensation level                                                              |   |          | 4.00      |   |          |   | 4.00 |   |
| Mortality table                                                                                                        |   | RP 2000       |      |   | RP 2000       |   |

|   | ● | Voluntary contributions were made to the Xcel Energy Pension Plan of $34 million in 2010. |
|--------|---------|-------------------------------------------------------------------------------------------|

|   | ● | Voluntary contributions were made to the PSCo Bargaining Pension Plan of $173 million in 2009. |
|--------|---------|------------------------------------------------------------------------------------------------|

|   | ● | Voluntary contributions were made to the NCE Non-Bargaining Pension Plan of $27 million in 2009. |
|--------|---------|-------------------------------------------------------------------------------------------------------|

|   | ● | Voluntary contributions were made across three of Xcel Energy’s pension plans for $134 million in January 2011.  The contribution raised the overall funded status from 84 percent at Dec. 31, 2010 to 88 percent with all other pension assumptions remaining constant. |
|--------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | ● | Pension funding contributions for 2012, which will be dependent on several factors including, realized asset performance, future discount rate, IRS and legislative initiatives as well as other actuarial assumptions, are estimated to range between $150 million to $175 million. |
|--------|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

|                                                      |   |   |     |   |   |   |     |   |   |
|-----------------------------------------------------------|--------|--------|----------|--------|--------|--------|----------|--------|--------|
| (Thousands of Dollars)                                    |   | 2010   |     |   | 2009   |   |     | 2008   |   |
| Service cost                                              |   | $      | 73,147   |   |   | $      | 65,461   |   |   | $ | 62,698 |   |
| Interest cost                                             |   |   | 165,010  |   |   |   | 169,790  |   |   |   | 167,881 |   |
| Expected return on plan assets                            |   |   | (232,318 | )      |   |   | (256,538 | )      |   |   | (274,338 | ) |
| Amortization of prior service cost                        |   |   | 20,657   |   |   |   | 24,618   |   |   |   | 20,584 |   |
| Amortization of net loss                                  |   |   | 48,315   |   |   |   | 12,455   |   |   |   | 11,156 |   |
| Net periodic pension cost(credit)                         |   | $      | 74,811   |   |   | $      | 15,786   |   |   | $ | (12,019 | ) |
| PSCo:                                                     |   |   |     |   |   |   |     |   |   |   |   |   |
| Net periodic pension cost                                 |   | $      | 15,303   |   |   | $      | 13,847   |   |   | $ | 11,120 |   |
| Significant Assumptions Used to Measure Costs:            |   |   |     |   |   |   |     |   |   |   |   |   |
| Discount rate                                             |   |   | 6.00     | %      |   |   | 6.75     | %      |   |   | 6.25 | % |
| Expected average long-term increase in compensation level |   |   | 4.00     |   |   |   | 4.00     |   |   |   | 4.00 |   |
| Expected average long-term rate of return on assets       |   |   | 7.79     |   |   |   | 8.50     |   |   |   | 8.75 |   |

----

Index

|                                               |   | Dec. 31, 2010 |    |
|----------------------------------------------------|--------|---------------|---------|
|                                               |   |          |    |   |   |   |   |   |   |   |   |   |
| (Thousands of Dollars)                             |   | Level 1       |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |
| Cash equivalents                                   |   | $             | 72,573  |   |   | $ | 76,352 |   |   | $ | — |   |   | $ | 148,925 |   |
| Derivatives                                        |   |          | — |   |   |   | 13,632 |   |   |   | — |   |   |   | 13,632 |   |
| Government securities                              |   |          | — |   |   |   | 3,402 |   |   |   | — |   |   |   | 3,402 |   |
| Corporate bonds                                    |   |          | — |   |   |   | 70,752 |   |   |   | — |   |   |   | 70,752 |   |
| Asset-backed securities                            |   |          | — |   |   |   | — |   |   |   | 2,585 |   |   |   | 2,585 |   |
| Mortgage-backed securities                         |   |          | — |   |   |   | — |   |   |   | 19,212 |   |   |   | 19,212 |   |
| Preferred stock                                    |   |          | — |   |   |   | 507 |   |   |   | — |   |   |   | 507 |   |
| Commingled equity and bond funds                   |   |          | — |   |   |   | 102,962 |   |   |   | — |   |   |   | 102,962 |   |
| Securities lending collateral obligation and other |   |          | — |   |   |   | 70,253 |   |   |   | — |   |   |   | 70,253 |   |
| Total                                              |   | $             | 72,573  |   |   | $ | 337,860 |   |   | $ | 21,797 |   |   | $ | 432,230 |   |
|                                               |   |          |    |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                                               |   | Dec. 31, 2009 |    |
|                                               |   |          |    |   |   |   |   |   |   |   |   |   |   |   |   |   |
| (Thousands of Dollars)                             |   | Level 1       |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |
| Cash equivalents                                   |   | $             | — |   |   | $ | 165,291 |   |   | $ | — |   |   | $ | 165,291 |   |
| Short-term investments                             |   |          | — |   |   |   | 2,226 |   |   |   | — |   |   |   | 2,226 |   |
| Derivatives                                        |   |          | — |   |   |   | 5,937 |   |   |   | — |   |   |   | 5,937 |   |
| Government securities                              |   |          | — |   |   |   | 1,538 |   |   |   | — |   |   |   | 1,538 |   |
| Corporate bonds                                    |   |          | — |   |   |   | 60,416 |   |   |   | — |   |   |   | 60,416 |   |
| Asset-backed securities                            |   |          | — |   |   |   | — |   |   |   | 8,293 |   |   |   | 8,372 |   |
| Mortgage-backed securities                         |   |          | — |   |   |   | — |   |   |   | 47,078 |   |   |   | 46,999 |   |
| Preferred stock                                    |   |          | — |   |   |   | 540 |   |   |   | — |   |   |   | 540 |   |
| Commingled equity and bond funds                   |   |          | — |   |   |   | 89,296 |   |   |   | — |   |   |   | 89,296 |   |
| Securities lending collateral obligation and other |   |          | — |   |   |   | 4,074 |   |   |   | — |   |   |   | 4,074 |   |
| Total                                              |   | $             | — |   |   | $ | 329,318 |   |   | $ | 55,371 |   |   | $ | 384,689 |   |

| (Thousands of Dollars)     |   |  Jan. 1, 2010 |   |   | Realized and Unrealized Gains       |   |   | Purchases, Issuances, and Settlements, net |   |   | Dec. 31, 2010 |   |
|----------------------------|--------|--------------------|--------|--------|-------------------------------------|--------|--------|--------------------------------------------|--------|--------|---------------|--------|
| Asset-backed securities    |   | $                  | 8,293  |   |                                | $      | 1,814  |                                       |   | $      | (7,522        | )      |   | $ | 2,585 |   |
| Mortgage-backed securities |   |               | 47,078 |   |                                |   | 14,715 |                                       |   |   | (42,581       | )      |   |   | 19,212 |   |
|                       |   |               |   |   |                                |   |   |                                       |   |   |          |   |   |   |   |
| (Thousands of Dollars)     |   |  Jan. 1, 2009 |   |   |  Realized and Unrealized Gains |   |   | Purchases, Issuances, and Settlements, net |   |   | Dec. 31, 2009 |   |
| Asset-backed securities    |   | $                  | 8,705  |   |                                | $      | 1,029  |                                       |   | $      | (1,441        | )      |   | $ | 8,293 |   |
| Mortgage-backed securities |   |               | 69,988 |   |                                |   | 3,022  |                                       |   |   | (25,932       | )      |   |   | 47,078 |   |

----

Index

| (Thousands of Dollars)                                                                                                 |   | 2010          |     |   | 2009          |   |
|------------------------------------------------------------------------------------------------------------------------|--------|---------------|----------|--------|---------------|--------|
| Change in Projected Benefit Obligation:                                                                                |   |          |     |   |          |   |
| Obligation at Jan. 1                                                                                                   |   | $             | 728,902  |   |          | $      | 794,597 |   |
| Service cost                                                                                                           |   |          | 4,006    |   |          |   | 4,665 |   |
| Interest cost                                                                                                          |   |          | 42,780   |   |          |   | 50,412 |   |
| Medicare subsidy reimbursements                                                                                        |   |          | 5,423    |   |          |   | 3,226 |   |
| Amendments                                                                                                             |   |          | —  |   |          |   | (27,407 | ) |
| Plan participants’ contributions                                                                                 |   |          | 14,315   |   |          |   | 13,786 |   |
| Actuarial loss (gain)                                                                                                  |   |          | 68,126   |   |          |   | (47,446 | ) |
| Benefit payments                                                                                                       |   |          | (68,647  | )      |          |   | (62,931 | ) |
| Obligation at Dec. 31                                                                                                  |   | $             | 794,905  |   |          | $      | 728,902 |   |
| Change in Fair Value of Plan Assets:                                                                                   |   |          |     |   |          |   |   |   |
| Fair value of plan assets at Jan. 1                                                                                    |   | $             | 384,689  |   |          | $      | 299,566 |   |
| Actual return on plan assets                                                                                           |   |          | 53,430   |   |          |   | 72,101 |   |
| Plan participants’ contributions                                                                                 |   |          | 14,315   |   |          |   | 13,786 |   |
| Employer contributions                                                                                                 |   |          | 48,443   |   |          |   | 62,167 |   |
| Benefit payments                                                                                                       |   |          | (68,647  | )      |          |   | (62,931 | ) |
| Fair value of plan assets at Dec. 31                                                                                   |   | $             | 432,230  |   |          | $      | 384,689 |   |
| Funded Status at Dec. 31:                                                                                              |   |          |     |   |          |   |   |   |
| Funded status                                                                                                          |   | $             | (362,675 | )      |          | $      | (344,213 | ) |
| Current liabilities                                                                                                    |   |          | (5,392   | )      |          |   | (2,240 | ) |
| Noncurrent liabilities                                                                                                 |   |          | (357,283 | )      |          |   | (341,973 | ) |
| Net postretirement amounts recognized on consolidated balance sheets                                                   |   | $             | (362,675 | )      |          | $      | (344,213 | ) |
| PSCo Amounts Not Yet Recognized as Components of Net Periodic Cost:                                                    |   |          |     |   |          |   |   |   |
| Net loss                                                                                                               |   | $             | 141,944  |   |          | $      | 110,766 |   |
| Prior service credit                                                                                                   |   |          | (22,349  | )      |          |   | (25,262 | ) |
| Transition obligation                                                                                                  |   |          | 22,793   |   |          |   | 33,797 |   |
| Total                                                                                                                  |   | $             | 142,388  |   |          | $      | 119,301 |   |
|                                                                                                                   |   |          |     |   |          |   |   |   |
| Amounts Related to the Funded Status of the Plans Have Been Recorded as Follows Based Upon Expected Recovery in Rates: |   |          |     |   |          |   |   |   |
| Regulatory assets                                                                                                      |   | $             | 142,388  |   |          | $      | 119,301 |   |
| PSCo accrued benefit liability recorded                                                                                |   |          | 165,653  |   |          |   | 148,022 |   |
| Measurement Date                                                                                                       |   | Dec. 31, 2010 |     |   | Dec. 31, 2009 |   |
|                                                                                                                   |   |          |     |   |          |   |   |   |
| Significant Assumptions Used to Measure Benefit Obligations:                                                           |   |          |     |   |          |   |   |   |
| Discount rate for year-end valuation                                                                                   |   |          | 5.50     | %      |          |   | 6.00 | % |
| Mortality table                                                                                                        |   | RP 2000       |     |   | RP 2000       |   |
| Health care costs trend rate - initial                                                                                 |   |          | 6.50     | %      |          |   | 6.80 | % |

----

Index

|                            |   | One Percentage Point |   |
|---------------------------------|--------|----------------------|--------|
| (Thousands of Dollars)          |   | Increase             |   |   | Decrease |   |
| APBO                            |   | $                    | 98,812 |   |   | $ | (76,175 | ) |
| Service and interest components |   |                 | 5,006  |   |   |   | (4,193 | ) |

|                                                             |   |   |    |   |   |   |    |   |   |
|------------------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| (Thousands of Dollars)                                           |   | 2010   |    |   | 2009   |   |    | 2008   |   |
| Service cost                                                     |   | $      | 4,006   |   |   | $      | 4,665   |   |   | $ | 5,350 |   |
| Interest cost                                                    |   |   | 42,780  |   |   |   | 50,412  |   |   |   | 51,047 |   |
| Expected return on plan assets                                   |   |   | (28,529 | )      |   |   | (22,775 | )      |   |   | (31,851 | ) |
| Amortization of transition obligation                            |   |   | 14,444  |   |   |   | 14,444  |   |   |   | 14,577 |   |
| Amortization of prior service cost                               |   |   | (4,932  | )      |   |   | (2,726  | )      |   |   | (2,175 | ) |
| Amortization of net loss                                         |   |   | 11,643  |   |   |   | 19,329  |   |   |   | 11,498 |   |
| Net periodic postretirement benefit cost                         |   |   | 39,412  |   |   |   | 63,349  |   |   |   | 48,446 |   |
| PSCo:                                                            |   |   |    |   |   |   |    |   |   |   |   |   |
| Net periodic postretirement benefit cost recognized              |   |   | 22,306  |   |   |   | 40,277  |   |   |   | 26,989 |   |
| Additional cost recognized due to effects of regulation          |   |   | 3,891   |   |   |   | 3,891   |   |   |   | 3,891 |   |
| Net benefit cost recognized for financial reporting              |   | $      | 26,197  |   |   | $      | 44,168  |   |   | $ | 30,880 |   |
| Significant Assumptions Used to Measure Costs:                   |   |   |    |   |   |   |    |   |   |   |   |   |
| Discount rate                                                    |   |   | 6.00    | %      |   |   | 6.75    | %      |   |   | 6.25 | % |
| Expected average long-term rate of return on assets (before tax) |   |   | 7.50    |   |   |   | 7.50    |   |   |   | 7.50 |   |

|                   |   |                             |      |   |                                                          |   |    |                               |   |   |                                                        |   |
|------------------------|--------|----------------------------------|-----------|--------|---------------------------------------------------------------|--------|---------|------------------------------------|--------|--------|-------------------------------------------------------------|--------|
| (Thousands of Dollars) |   | ProjectedPension BenefitPayments |      |   | Gross ProjectedPostretirementHealth CareBenefit Payments |   |    | Expected Medicare Part D Subsidies |   |   | Net ProjectedPostretirementHealth CareBenefit Payments |   |
| 2011                   |   | $                                | 254,426   |   |                                                          | $      | 59,752  |                               |   | $      | 4,770                                                       |   |   | $ | 54,982 |   |
| 2012                   |   |                             | 247,156   |   |                                                          |   | 60,230  |                               |   |   | 5,126                                                       |   |   |   | 55,104 |   |
| 2013                   |   |                             | 249,908   |   |                                                          |   | 60,607  |                               |   |   | 5,475                                                       |   |   |   | 55,132 |   |
| 2014                   |   |                             | 257,886   |   |                                                          |   | 61,833  |                               |   |   | 5,773                                                       |   |   |   | 56,060 |   |
| 2015                   |   |                             | 259,978   |   |                                                          |   | 63,184  |                               |   |   | 6,061                                                       |   |   |   | 57,123 |   |
| 2016-2020              |   |                             | 1,338,658 |   |                                                          |   | 325,154 |                               |   |   | 34,115                                                      |   |   |   | 291,039 |   |

----

Index

|                               |   |   |    |   |   |   |    |   |   |
|------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| (Thousands of Dollars)             |   | 2010   |    |   | 2009   |   |    | 2008   |   |
| Interest income                    |   | $      | 3,296   |   |   | $      | 3,247   |   |   | $ | 10,283 |   |
| COLI settlement (See Note 7)       |   |   | 25,000  |   |   |   | — |   |   |   | — |   |
| Other nonoperating income          |   |   | 1,758   |   |   |   | 3,192   |   |   |   | 2,954 |   |
| Insurance policy (expenses) income |   |   | (937    | )      |   |   | (1,348  | )      |   |   | 3,515 |   |
| Other nonoperating expenses        |   |   | — |   |   |   | (395    | )      |   |   | (4 | ) |
| Other income, net                  |   | $      | 29,117  |   |   | $      | 4,696   |   |   | $ | 16,748 |   |

|                                |   |          |   |   |          |   |
|-------------------------------------|--------|---------------|--------|--------|---------------|--------|
| (Amounts in Thousands)(a)           |   | Dec. 31, 2010 |   |   | Dec. 31, 2009 |   |
| Megawatt hours (MWh) of electricity |   |          | 2,418  |   |          |   | 3,559 |   |
| MMBtu of natural gas                |   |          | 59,465 |   |          |   | 45,352 |   |
| Gallons of vehicle fuel             |   |          | 360    |   |          |   | 1,559 |   |

----

Index

| (Thousands of Dollars)                                                                      |   | 2010   |   |   | 2009   |   |   | 2008   |   |
|---------------------------------------------------------------------------------------------|--------|--------|--------|--------|--------|--------|--------|--------|--------|
| Accumulated other comprehensive income related to cash flow hedges at Jan. 1                |   | $      | 8,101  |   |   | $      | 7,628  |   |   | $ | 12,447 |   |
| After-tax net unrealized (losses) gains related to derivatives accounted for as hedges      |   |   | (63    | )      |   |   | 315    |   |   |   | (3,294 | ) |
| After-tax net realized (gains) losses on derivative transactions reclassified into earnings |   |   | (581   | )      |   |   | 158    |   |   |   | (1,525 | ) |
| Accumulated other comprehensive income related to cash flow hedges at Dec. 31               |   | $      | 7,457  |   |   | $      | 8,101  |   |   | $ | 7,628 |   |

|                                       |   |                                               |    |   |                                                                  |   |    |                                                          |   |
|--------------------------------------------|--------|----------------------------------------------------|---------|--------|-----------------------------------------------------------------------|--------|---------|---------------------------------------------------------------|--------|
|                                       |   | Dec. 31, 2010                                      |    |
|                                       |   | Fair Value Changes RecognizedDuring the Period in: |    |   |  Pre-Tax Amounts Reclassified intoIncome During the Period from: |   |    | Pre-Tax Gains (Losses) Recognized During the Period in Income |   |
| (Thousands of Dollars)                     |   | OtherComprehensiveLosses                           |    |   | RegulatoryAssets andLiabilities                                       |   |    | OtherComprehensiveIncome (Losses)                             |   |   | RegulatoryAssets andLiabilities |   |   |   |
| Derivatives designated as cash flow hedges |   |                                               |    |   |                                                                  |   |    |                                                          |   |   |   |   |   |   |   |
| Interest rate                              |   | $                                                  | — |   |                                                                  | $      | — |                                                          |   | $ | (2,336 | )(a) |   | $ | — |   |   | $ | — |   |
| Vehicle fuel and other commodity           |   |                                               | (101    | )      |                                                                  |   | — |                                                          |   |   | 1,399 | (c) |   |   | — |   |   |   | — |   |
| Total                                      |   | $                                                  | (101    | )      |                                                                  | $      | — |                                                          |   | $ | (937 | ) |   | $ | — |   |   | $ | — |   |
|                                       |   |                                               |    |   |                                                                  |   |    |                                                          |   |   |   |   |   |   |   |   |   |   |   |   |
| Other derivative instruments               |   |                                               |    |   |                                                                  |   |    |                                                          |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                          |   | $                                                  | — |   |                                                                  | $      | — |                                                          |   | $ | — |   |   | $ | — |   |   | $ | (1,058 | )(b) |
| Natural gas commodity                      |   |                                               | — |   |                                                                  |   | (83,295 | )                                                             |   |   | — |   |   |   | 40,862 | (d) |   |   | — |   |
| Other                                      |   |                                               | — |   |                                                                  |   | — |                                                          |   |   | — |   |   |   | — |   |   |   | 135 | (b) |
| Total                                      |   | $                                                  | — |   |                                                                  | $      | (83,295 | )                                                             |   | $ | — |   |   | $ | 40,862 |   |   | $ | (923 | ) |

----

Index

|                                       |   | Dec. 31, 2009                                      |    |
|--------------------------------------------|--------|----------------------------------------------------|---------|
|                                       |   | Fair Value Changes RecognizedDuring the Period in: |    |   | Pre-Tax Amounts Reclassified intoIncome During the Period from: |   |   | Pre-Tax Gains (Losses) Recognized During the Period in Income |   |
| (Thousands of Dollars)                     |   | OtherComprehensiveIncome (Losses)                  |    |   | RegulatoryAssets andLiabilities |   |   | OtherComprehensiveIncome (Losses) |   |   | RegulatoryAssets andLiabilities |   |   |   |
| Derivatives designated as cash flow hedges |   |                                               |    |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest rate                              |   | $                                                  | (632    | ) |   | $ | — |   |   | $ | (2,361 | )(a) |   | $ | — |   |   | $ | — |   |
| Natural gas commodity                      |   |                                               | — |   |   |   | (14,641 | ) |   |   | — |   |   |   | 66,311 | (d) |   |   | (22,243 | )(d) |
| Vehicle fuel and other commodity           |   |                                               | 1,140   |   |   |   | — |   |   |   | 2,624 | (c) |   |   | — |   |   |   | — |   |
| Total                                      |   | $                                                  | 508     |   |   | $ | (14,641 | ) |   | $ | 263 |   |   | $ | 66,311 |   |   | $ | (22,243 | ) |
| Other derivative instruments               |   |                                               |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                          |   | $                                                  | — |   |   | $ | — |   |   | $ | — |   |   | $ | — |   |   | $ | 2,009 | (b) |
| Natural gas commodity                      |   |                                               | — |   |   |   | 3,880 |   |   |   | — |   |   |   | 8,190 | (d) |   |   | — |   |
| Total                                      |   | $                                                  | — |   |   | $ | 3,880 |   |   | $ | — |   |   | $ | 8,190 |   |   | $ | 2,009 |   |

| (a) | Recorded to interest charges                                                                                                                                                                                                                                                          |
|-----|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (b) | Recorded to electric operating revenues.  Portions of these total gains and losses are subject to sharing with electric customers through margin-sharing mechanisms and deducted from gross revenue, as appropriate.                                                   |
| (c) | Recorded to other O&M expenses.                                                                                                                                                                                                                                                   |
| (d) | Recorded to cost of natural gas sold and transported; these derivative settlement gains and losses are shared with natural gas customers through purchased natural gas cost-recovery mechanisms, and reclassified out of income as regulatory assets and liabilities, as appropriate. |

----

Index

|                                        |   | Dec. 31, 2010    |    |
|---------------------------------------------|--------|------------------|---------|
|                                        |   |  Fair Value |    |   |   |   |   |   |   |   |   |   |
|                                        |   |             |    |   |   |   |   |   |   |   | Fair Value |   |   | Counterparty |   |   |   |   |
| (Thousands of Dollars)                      |   | Level 1          |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |   | Netting (b) |   |   | Total |   |
| Current derivative assets                   |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Derivatives designated as cash flow hedges: |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Vehicle fuel and other commodity            |   | $                | — |   |   | $ | 56 |   |   | $ | — |   |   | $ | 56 |   |   | $ | — |   |   | $ | 56 |   |
| Other derivative instruments:               |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   |             | — |   |   |   | 5,765 |   |   |   | — |   |   |   | 5,765 |   |   |   | (2,633 | ) |   |   | 3,132 |   |
| Natural gas commodity                       |   |             | — |   |   |   | 1,396 |   |   |   | — |   |   |   | 1,396 |   |   |   | (1,019 | ) |   |   | 377 |   |
| Total current derivative assets             |   | $                | — |   |   | $ | 7,217 |   |   | $ | — |   |   | $ | 7,217 |   |   | $ | (3,652 | ) |   |   | 3,565 |   |
| Purchased power agreements (a)              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 2,729 |   |
| Current derivative instruments              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 6,294 |   |
| Noncurrent derivative assets                |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Derivatives designated as cash flow hedges: |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Vehicle fuel and other commodity            |   | $                | — |   |   | $ | 68 |   |   | $ | — |   |   | $ | 68 |   |   | $ | — |   |   | $ | 68 |   |
| Other derivative instruments:               |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   |             | — |   |   |   | 6,770 |   |   |   | — |   |   |   | 6,770 |   |   |   | (2,118 | ) |   |   | 4,652 |   |
| Natural gas commodity                       |   |             | — |   |   |   | 1,111 |   |   |   | — |   |   |   | 1,111 |   |   |   | (211 | ) |   |   | 900 |   |
| Total noncurrent derivative assets          |   | $                | — |   |   | $ | 7,949 |   |   | $ | — |   |   | $ | 7,949 |   |   | $ | (2,329 | ) |   |   | 5,620 |   |
| Purchased power agreements (a)              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 12,415 |   |
| Noncurrent derivative instruments           |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 18,035 |   |
|                                        |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Current derivative liabilities              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Other derivative instruments:               |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   | $                | — |   |   | $ | 5,192 |   |   | $ | — |   |   | $ | 5,192 |   |   | $ | (2,669 | ) |   | $ | 2,523 |   |
| Natural gas commodity                       |   |             | — |   |   |   | 41,753 |   |   |   | — |   |   |   | 41,753 |   |   |   | (20,969 | ) |   |   | 20,784 |   |
| Total current derivative liabilities        |   | $                | — |   |   | $ | 46,945 |   |   | $ | — |   |   | $ | 46,945 |   |   | $ | (23,638 | ) |   |   | 23,307 |   |
| Purchased power agreements (a)              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 5,740 |   |
| Current derivative instruments              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 29,047 |   |
| Noncurrent derivative liabilities           |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Other derivative instruments:               |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   | $                | — |   |   | $ | 5,526 |   |   | $ | — |   |   | $ | 5,526 |   |   | $ | (2,118 | ) |   | $ | 3,408 |   |
| Natural gas commodity                       |   |             | — |   |   |   | 350 |   |   |   | — |   |   |   | 350 |   |   |   | (211 | ) |   |   | 139 |   |
| Total noncurrent derivative liabilities     |   | $                | — |   |   | $ | 5,876 |   |   | $ | — |   |   | $ | 5,876 |   |   | $ | (2,329 | ) |   |   | 3,547 |   |
| Purchased power agreements (a)              |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 39,673 |   |
| Noncurrent derivative instruments           |   |             |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 43,220 |   |

| (a) | In 2003, as a result of implementing new guidance on the normal purchase exception for derivative accounting, PSCo began recording several long-term purchased power agreements at fair value due to accounting requirements related to underlying price adjustments. As these purchases are recovered through normal regulatory recovery mechanisms in the respective jurisdictions, the changes in fair value for these contracts were offset by regulatory assets and liabilities. During 2006, PSCo qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities. |
|-----|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (b) | The accounting for derivatives and hedging permits the netting of receivables and payables for derivatives and related collateral amounts when a legally  enforceable master netting agreement exists between PSCo and a counterparty. A master netting agreement is an agreement between two parties who    have multiple contracts with each other that provides for the net settlement of all contracts in the event of default on or termination of any one contract.                                                                                                                                                                                                                                                                                                                              |

----

Index

|                                                              |   |         |   |
|-------------------------------------------------------------------|--------|--------------|--------|
|                                                              |   | From Level 3 |   |
| (Thousands of Dollars)                                            |   | to Level 2   |   |
| Trading commodity derivatives not designated as cash flow hedges: |   |         |   |
| Current assets                                                    |   | $            | 1,888  |   |
| Noncurrent assets                                                 |   |         | 4,988  |   |
| Current liabilities                                               |   |         | (1,265 | ) |
| Noncurrent liabilities                                            |   |         | (3,724 | ) |
| Total                                                             |   | $            | 1,887  |   |

|                                        |   |                |    |
|---------------------------------------------|--------|---------------------|---------|
|                                        |   |  Dec. 31, 2009 |    |
|                                        |   | Fair Value          |    |   |   |   |   |   |   |   |   |   |
|                                        |   |                |    |   |   |   |   |   |   |   | Fair Value |   |   | Counterparty |   |   |   |   |
| (Thousands of Dollars)                      |   | Level 1             |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |   | Netting (b) |   |   | Total |   |
| Current derivative assets                   |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Other derivative instruments:               |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   | $                   | — |   |   | $ | 2,380 |   |   | $ | 986 |   |   | $ | 3,366 |   |   | $ | (2,120 | ) |   | $ | 1,246 |   |
| Natural gas commodity                       |   |                | — |   |   |   | 8,752 |   |   |   | — |   |   |   | 8,752 |   |   |   | 111 |   |   |   | 8,863 |   |
| Total current derivative assets             |   | $                   | — |   |   | $ | 11,132 |   |   | $ | 986 |   |   | $ | 12,118 |   |   | $ | (2,009 | ) |   |   | 10,109 |   |
| Purchased power agreements (a)              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 18,595 |   |
| Current derivative instruments              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 28,704 |   |
| Noncurrent derivative assets                |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Derivatives designated as cash flow hedges: |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Vehicle fuel and other commodity            |   | $                   | — |   |   | $ | 69 |   |   | $ | — |   |   | $ | 69 |   |   | $ | — |   |   | $ | 69 |   |
| Other derivative instruments:               |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   |                | — |   |   |   | 1,514 |   |   |   | 1,535 |   |   |   | 3,049 |   |   |   | 677 |   |   |   | 3,726 |   |
| Natural gas commodity                       |   |                | — |   |   |   | 476 |   |   |   | — |   |   |   | 476 |   |   |   | 248 |   |   |   | 724 |   |
| Total noncurrent derivative assets          |   | $                   | — |   |   | $ | 2,059 |   |   | $ | 1,535 |   |   | $ | 3,594 |   |   | $ | 925 |   |   |   | 4,519 |   |
| Purchased power agreements (a)              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 100,145 |   |
| Noncurrent derivative instruments           |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 104,664 |   |

----

Index

|                                        |   |  Dec. 31, 2009 |    |
|---------------------------------------------|--------|---------------------|---------|
|                                        |   |  Fair Value    |    |   |   |   |   |   |   |   |   |   |
|                                        |   |                |    |   |   |   |   |   |   |   | Fair Value |   |   | Counterparty |   |   |   |   |
| (Thousands of Dollars)                      |   | Level 1             |    |   | Level 2 |   |   | Level 3 |   |   | Total |   |   | Netting (b) |   |   | Total |   |
| Current derivative liabilities              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Derivatives designated as cash flow hedges: |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Vehicle fuel and other commodity            |   | $                   | — |   |   | $ | 1,338 |   |   | $ | — |   |   | $ | 1,338 |   |   | $ | — |   |   | $ | 1,338 |   |
| Other derivative instruments:               |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   |                | — |   |   |   | 3,555 |   |   |   | 834 |   |   |   | 4,389 |   |   |   | (2,589 | ) |   |   | 1,800 |   |
| Natural gas commodity                       |   |                | — |   |   |   | 6,090 |   |   |   | — |   |   |   | 6,090 |   |   |   | 111 |   |   |   | 6,201 |   |
| Total current derivative liabilities        |   | $                   | — |   |   | $ | 10,983 |   |   | $ | 834 |   |   | $ | 11,817 |   |   | $ | (2,478 | ) |   |   | 9,339 |   |
| Purchased power agreements (a)              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 8,946 |   |
| Current derivative instruments              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 18,285 |   |
|                                        |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Noncurrent derivative liabilities           |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Other derivative instruments:               |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Trading commodity                           |   | $                   | — |   |   | $ | 489 |   |   | $ | 883 |   |   | $ | 1,372 |   |   | $ | 676 |   |   | $ | 2,048 |   |
| Natural gas commodity                       |   |                | — |   |   |   | 302 |   |   |   | — |   |   |   | 302 |   |   |   | 248 |   |   |   | 550 |   |
| Total noncurrent derivative liabilities     |   | $                   | — |   |   | $ | 791 |   |   | $ | 883 |   |   | $ | 1,674 |   |   | $ | 924 |   |   |   | 2,598 |   |
| Purchased power agreements (a)              |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | 46,989 |   |
| Noncurrent derivative instruments           |   |                |    |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   | $ | 49,587 |   |

| (a)    | In 2003, as a result of implementing new guidance on the normal purchase exception for derivative accounting, PSCo began recording several long-term purchased power agreements at fair value due to accounting requirements related to underlying price adjustments.  As these purchases are recovered through normal regulatory recovery mechanisms in the respective jurisdictions, the changes in fair value for these contracts were offset by regulatory assets and  liabilities.  During 2006, PSCo qualified these contracts under the normal purchase exception.  Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities. |
|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| (b)    | The accounting guidance for derivatives and hedging permits the netting of receivables and payables for derivatives and related collateral amounts when a legally enforceable master netting agreement exists between PSCo and a counterparty. A master netting agreement is an agreement between two parties who have multiple contracts with each other that provides for the net settlement of all contracts in the event of default on or termination of any one contract.                                                                                                                                                                                                                                                                                                                                                                                         |

----

Index

|                                                  |   |                |    |
|-------------------------------------------------------|--------|---------------------|---------|
|                                                  |   | Year Ended Dec. 31, |    |
|                                                  |   |                |    |   |   |   |   |   |   |
| (Thousands of Dollars)                                |   | 2010                |    |   | 2009 |   |   | 2008 |   |
| Balance at Jan. 1                                     |   | $                   | 804     |   |   | $ | (26 | ) |   | $ | 4,121 |   |
| Purchases, issuances, and settlements, net            |   |                | (570    | ) |   |   | (3,668 | ) |   |   | (4,396 | ) |
| Transfers (out of) into Level 3                       |   |                | (1,887  | ) |   |   | 579 |   |   |   | — |   |
| Gains (losses) recognized in earnings                 |   |                | 1,653   |   |   |   | 2,535 |   |   |   | (1,384 | ) |
| Gains recognized as regulatory assets and liabilities |   |                | — |   |   |   | 1,384 |   |   |   | 1,633 |   |
| Balance at Dec. 31                                    |   | $                   | — |   |   | $ | 804 |   |   | $ | (26 | ) |

|                                      |   |     |      |   |       |   |      |     |   |   |       |   |
|-------------------------------------------|--------|----------|-----------|--------|------------|--------|-----------|----------|--------|--------|------------|--------|
|                                      |   | 2010     |      |   | 2009       |   |
|                                      |   | Carrying |      |   |       |   |      | Carrying |   |   |       |   |
| (Thousands of Dollars)                    |   | Amount   |      |   | Fair Value |   |      | Amount   |   |   | Fair Value |   |
| Other investments                         |   | $        | 8         |   |       | $      | 8         |     |   | $      | 8          |   |   | $ | 8 |   |
| Long-term debt, including current portion |   |     | 3,235,223 |   |       |   | 3,531,729 |     |   |   | 2,828,952  |   |   |   | 3,050,249 |   |

----

Index

|   | ● | A rate increase of $67 million was implemented on Jan. 1, 2010. |
|--------|---------|---------------------------------------------------------------------------|

|   | ● | In May 2010, base rates were increased to recover $125 million annually, when Comanche Unit 3 went into service. |
|--------|---------|----------------------------------------------------------------------------------------------------------------------------|

|   | ● | Base rates increased to recover approximately $130 million annually on Jan. 1, 2011, to reflect 2011 property taxes. |
|--------|---------|--------------------------------------------------------------------------------------------------------------------------------|

|                       |   |      |   |   |   |   |   | Carbon  |   |
|----------------------------|--------|-----------|--------|--------|--------|--------|--------|---------|--------|
| Margin                     |   | Customers |   |   | PSCo   |   |   | Offsets |   |
| Less than $10 million      |   |      | 50     | %      |   |   | 40     | %       |   |   | 10 | % |
| $10 million to $30 million |   |      | 55     |   |   |   | 35     |    |   |   | 10 |   |
| Greater than $30 million   |   |      | 60     |   |   |   | 30     |    |   |   | 10 |   |

----

Index

| (Millions of Dollars)                    |   |   |    |
|------------------------------------------|--------|--------|---------|
| Coal                                     |   | $      | 327.3   |   |
| Natural gas supply                       |   |   | 1,142.8 |   |
| Natural gas storage & transportation |   |   | 1,811.8 |   |

----

Index

| (Millions of Dollars) |   |   |   |
|-----------------------|--------|--------|--------|
| 2011                  |   | $      | 182.0  |   |
| 2012                  |   |   | 122.8  |   |
| 2013                  |   |   | 72.5   |   |
| 2014                  |   |   | 67.3   |   |
| 2015                  |   |   | 72.9   |   |
| 2016 and thereafter   |   |   | 101.7  |   |
| Total                 |   | $      | 619.2  |   |

| (Millions of Dollars)                         |   | 2010   |   |   | 2009   |   |
|-----------------------------------------------|--------|--------|--------|--------|--------|--------|
| Storage, leaseholds and rights                |   | $      | 196.1  |   |   | $      | 183.6 |   |
| Gas pipeline                                  |   |   | 20.7   |   |   |   | 20.7 |   |
| Property held under capital lease             |   |   | 216.8  |   |   |   | 204.3 |   |
| Accumulated depreciation                      |   |   | (26.6  | )      |   |   | (21.3 | ) |
| Total property held under capital leases, net |   | $      | 190.2  |   |   | $      | 183.0 |   |

----

Index

|                                |   |      |   |   | Purchase Power |   |   |      |   |   |    |   |
|-------------------------------------|--------|-----------|--------|--------|----------------|--------|--------|-----------|--------|--------|---------|--------|
|                                |   | Other     |   |   | Agreement      |   |   | Total     |   |   |    |   |
|                                |   | Operating |   |   | Operating      |   |   | Operating |   |   | Capital |   |
| (Millions of Dollars)               |   | Leases    |   |   | Leases (a) (b) |   |   | Leases    |   |   | Leases  |   |
| 2011                                |   | $         | 15.8   |   |           | $      | 44.6   |      |   | $      | 60.4    |   |   | $ | 31.4 |   |
| 2012                                |   |      | 14.6   |   |           |   | 55.7   |      |   |   | 70.3    |   |   |   | 29.7 |   |
| 2013                                |   |      | 14.1   |   |           |   | 73.1   |      |   |   | 87.2    |   |   |   | 29.5 |   |
| 2014                                |   |      | 14.3   |   |           |   | 79.3   |      |   |   | 93.6    |   |   |   | 29.4 |   |
| 2015                                |   |      | 14.0   |   |           |   | 79.7   |      |   |   | 93.7    |   |   |   | 27.0 |   |
| Thereafter                          |   |      | 42.1   |   |           |   | 677.8  |      |   |   | 719.9   |   |   |   | 606.8 |   |
| Total minimum obligation            |   |      |   |   |           |   |   |      |   |   |    |   |   |   | 753.8 |   |
| Interest component of obligation    |   |      |   |   |           |   |   |      |   |   |    |   |   |   | (563.6 | ) |
| Present value of minimum obligation |   |      |   |   |           |   |   |      |   |   |    |   |   | $ | 190.2 |   |

----

Index

----

Index

|                                   |   | Beginning    |   |   |        |   |    |        |   |   |      |   |   | Revisions |   |   | Ending        |   |
|----------------------------------------|--------|--------------|--------|--------|-------------|--------|---------|-------------|--------|--------|-----------|--------|--------|-----------|--------|--------|---------------|--------|
|                                   |   | Balance      |   |   | Liabilities |   |    | Liabilities |   |   |      |   |   | to Prior  |   |   | Balance       |   |
| (Thousands of Dollars)                 |   | Jan. 1, 2010 |   |   | Recognized  |   |    | Settled     |   |   | Accretion |   |   | Estimates |   |   | Dec. 31, 2010 |   |
| Electric plant                         |   |         |   |   |        |   |    |        |   |   |      |   |   |      |   |   |          |   |
| Steam production asbestos              |   | $            | 59,724 |   |        | $      | — |        |   | $      | —   |   |   | $         | 3,907  |   |          | $      | — |   |   | $ | 63,631 |   |
| Steam production ash containment       |   |         | 4,587  |   |        |   | 32      |        |   |   | —   |   |   |      | 272    |   |          |   | 1,637 |   |   |   | 6,528 |   |
| Steam production radiation sources     |   |         | 118    |   |        |   | — |        |   |   | —   |   |   |      | 8      |   |          |   | 1 |   |   |   | 127 |   |
| Electric transmission and distribution |   |         | 115    |   |        |   | — |        |   |   | —   |   |   |      | 7      |   |          |   | 1,624 |   |   |   | 1,746 |   |
| Natural gas plant                      |   |         |   |   |        |   |    |        |   |   |      |   |   |      |   |   |          |   |   |   |   |   |   |   |
| Gas transmission and distribution      |   |         | 616    |   |        |   | — |        |   |   | —   |   |   |      | 39     |   |          |   | — |   |   |   | 655 |   |
| Total liability                        |   | $            | 65,160 |   |        | $      | 32      |        |   | $      | —   |   |   | $         | 4,233  |   |          | $      | 3,262 |   |   | $ | 72,687 |   |

----

Index

|                                   |   |         |   |   |        |   |    |        |   |   |      |   |   |      |   |   |          |   |
|----------------------------------------|--------|--------------|--------|--------|-------------|--------|---------|-------------|--------|--------|-----------|--------|--------|-----------|--------|--------|---------------|--------|
|                                   |   | Beginning    |   |   |        |   |    |        |   |   |      |   |   | Revisions |   |   | Ending        |   |
|                                   |   | Balance      |   |   | Liabilities |   |    | Liabilities |   |   |      |   |   | to Prior  |   |   | Balance       |   |
| (Thousands of Dollars)                 |   | Jan. 1, 2009 |   |   | Recognized  |   |    | Settled     |   |   | Accretion |   |   | Estimates |   |   | Dec. 31, 2009 |   |
| Electric plant                         |   |         |   |   |        |   |    |        |   |   |      |   |   |      |   |   |          |   |
| Steam production asbestos              |   | $            | 56,125 |   |        | $      | — |        |   | $      | —   |   |   | $         | 3,671  |   |          | $      | (72 | ) |   | $ | 59,724 |   |
| Steam production ash containment       |   |         | 4,406  |   |        |   | — |        |   |   | —   |   |   |      | 261    |   |          |   | (80 | ) |   |   | 4,587 |   |
| Steam production radiation sources     |   |         | 276    |   |        |   | — |        |   |   | —   |   |   |      | 20     |   |          |   | (178 | ) |   |   | 118 |   |
| Electric transmission and distribution |   |         | 119    |   |        |   | — |        |   |   | —   |   |   |      | 7      |   |          |   | (11 | ) |   |   | 115 |   |
| Natural gas plant                      |   |         |   |   |        |   |    |        |   |   |      |   |   |      |   |   |          |   |   |   |   |   |   |   |
| Gas transmission and distribution      |   |         | 579    |   |        |   | — |        |   |   | —   |   |   |      | 37     |   |          |   | — |   |   |   | 616 |   |
| Total liability                        |   | $            | 61,505 |   |        | $      | — |        |   | $      | —   |   |   | $         | 3,996  |   |          | $      | (341 | ) |   | $ | 65,160 |   |

----

Index

----

Index

----

Index

|                                                        |   |   | See     |                       | Remaining           |   |   |          |    |       |          |    |    |       |   |    |    |   |
|-------------------------------------------------------------|--------|--------|---------|----------------------------|---------------------|--------|--------|---------------|---------|------------|---------------|---------|---------|------------|--------|---------|---------|--------|
| (Thousands of Dollars)                            |   |   | Note(s) |                       | Amortization Period |   |   | Dec. 31, 2010 |    |       | Dec. 31, 2009 |    |
|                                                        |   |   |    |                       |                |   |   | Current       |    | Noncurrent |          | Current |    | Noncurrent |   |
| Regulatory Assets                                           |   |   |    |                       |                |   |   |          |    |       |          |    |    |       |   |    |    |   |   |   |   |   |
| Recoverable purchased natural gas and electric energy costs |   | 1      |    | Less than one year         |                |   | $      | 18,622        |    |       | $             | — |    |       | $      | 25,157  |    |   | $ | — |   |
| Pension and employee benefit obligations (a)                |   | 8      |    | Various                    |                |   |   | 44,917        |    |       |          | 551,505 |    |       |   | 36,300  |    |   |   | 524,430 |   |
| AFUDC recorded in plant (b)                                 |   | 1      |    | Plant lives                |                |   |   | —       |    |       |          | 92,444  |    |       |   | — |    |   |   | 88,849 |   |
| Contract valuation adjustments (c)                          |   | 10     |    | Term of related contract   |                |   |   | 43,368        |    |       |          | 26,498  |    |       |   | — |    |   |   | — |   |
| Renewable and environmental initiative costs                |   | 13     |    | One to six years           |                |   |   | 47,961        |    |       |          | 4,500   |    |       |   | 25,984  |    |   |   | 5,181 |   |
| Net AROs (d)                                                |   | 1,13   |    | Plant lives                |                |   |   | —       |    |       |          | 43,227  |    |       |   | — |    |   |   | 33,725 |   |
| Conservation programs (b)                                   |   | 1      |    | Typically one to two years |                |   |   | 7,770         |    |       |          | 30,464  |    |       |   | 25,748  |    |   |   | 32,548 |   |
| Gas pipeline inspection costs                               |   |   |    |                       | Pending rate case   |   |   |          | 2,000   |       |          |    | 25,082  |       |   |    | 2,542   |   |   |   | 10,234 |   |
| Purchased power contracts costs                             |   | 10,13  |    | Term of related contract   |                |   |   | —       |    |       |          | 18,549  |    |       |   | — |    |   |   | 13,189 |   |
| Depreciation differences                                    |   |   |    |                       | One to seven years  |   |   |          | 5,859   |       |          |    | 12,379  |       |   |    | — |   |   |   | — |   |
| Losses on reacquired debt                                   |   | 1      |    | Term of related debt       |                |   |   | 1,912         |    |       |          | 14,750  |    |       |   | 1,912   |    |   |   | 16,662 |   |
| Other                                                       |   |   |    |                       | Various             |   |   |          | 4,187   |       |          |    | 4,807   |       |   |    | 4,518   |   |   |   | 5,489 |   |
| Total regulatory assets                                     |   |   |    |                       |                |   |   | $             | 176,596 |       |          | $       | 824,205 |       |   | $       | 122,161 |   |   | $ | 730,307 |   |
|                                                        |   |   |    |                       |                |   |   |          |    |       |          |    |    |       |   |    |    |   |   |   |   |   |
| Regulatory Liabilities                                      |   |   |    |                       |                |   |   |          |    |       |          |    |    |       |   |    |    |   |   |   |   |   |
| Deferred electric, gas, and steam production costs          |   | 1      |    |                       |                |   | $      | 44,921        |    |       | $             | — |    |       | $      | 64,552  |    |   | $ | — |   |
| Plant removal costs                                         |   | 1,13   |    |                       |                |   |   | —       |    |       |          | 384,640 |    |       |   | — |    |   |   | 374,555 |   |
| Investment tax credit deferrals                             |   | 1      |    |                       |                |   |   | —       |    |       |          | 29,014  |    |       |   | — |    |   |   | 30,662 |   |
| REC margin sharing                                          |   | 1,12   |    | Pending future rate case   |                |   |   | —       |    |       |          | 26,104  |    |       |   | — |    |   |   | — |   |
| Deferred income tax adjustment                              |   | 1      |    |                       |                |   |   | —       |    |       |          | 20,938  |    |       |   | — |    |   |   | 21,771 |   |
| Low income discount program                                 |   |   |    |                       |                |   |   |          | 4,706   |       |          |    | 4,032   |       |   |    | 2,526   |   |   |   | 2,017 |   |
| Gain from asset sales                                       |   | 1      |    | Pending future rate case   |                |   |   | —       |    |       |          | 6,700   |    |       |   | — |    |   |   | 10,329 |   |
| Contract valuation adjustments (c)                          |   | 10     |    |                       |                |   |   | —       |    |       |          | — |    |       |   | 12,312  |    |   |   | 53,329 |   |
| Other                                                       |   |   |    |                       |                |   |   |          | 391     |       |          |    | 1,418   |       |   |    | 1,074   |   |   |   | 1,916 |   |
| Total regulatory liabilities                                |   |   |    |                       |                |   |   | $             | 50,018  |       |          | $       | 472,846 |       |   | $       | 80,464  |   |   | $ | 494,579 |   |

| (a) | Includes $7.8 million and $11.7 million of unamortized prior service costs at Dec. 31, 2010 and Dec. 31, 2009, respectively. These amounts are offset by $4.5 and $4.2 million of regulatory assets related to the non-qualified pension plan of which $0.4 million is included in the current asset at Dec. 31, 2010 and Dec. 31, 2009. |
|-----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| (b) | Earns a return on investment in the ratemaking process. These amounts are amortized consistent with recovery in rates. |
|-----|------------------------------------------------------------------------------------------------------------------------|

| (c) | Includes the fair value of certain long-term PPAs used to meet energy capacity requirements. |
|-----|----------------------------------------------------------------------------------------------|

| (d) | Includes amounts recorded for future recovery of AROs. |
|-----|--------------------------------------------------------|

| ● | PSCo’s regulated electric utility segment generates, transmits and distributes electricity in Colorado.  In addition, this segment includes sales for resale and provides wholesale transmission service to various entities in the United States.  Regulated electric utility also includes PSCo’s commodity trading operations. |
|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ● | PSCo’s regulated natural gas utility segment transports, stores and distributes natural gas in portions of Colorado. |
|---------|----------------------------------------------------------------------------------------------------------------------------|

| ● | Revenues from operating segments not included above are below the necessary quantitative thresholds and are therefore included in the all other category.  Those primarily include steam revenue, appliance repair services and nonutility real estate activities. |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

|                                       | Regulated |     | Regulated |             | All    |   | Reconciling |         | Consolidated |   |
|--------------------------------------------|-----------|----------|-----------|------------------|--------|--------|-------------|--------------|--------------|--------|
| (Thousands of Dollars)           |      | Electric |      | Natural Gas |   | Other  |        | Eliminations |         | Total  |   |
| 2010                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |
| Operating revenues from external customers |      | $        | 3,055,045 |             |   | $      | 1,075,446   |         |         | $      | 33,879 |   |   | $ | — |   |   | $ | 4,164,370 |   |
| Intersegment revenues                      |      |     | 236       |             |   |   | 154         |         |         |   | — |   |   |   | (390 | ) |   |   | — |   |
| Total revenues                             |      | $        | 3,055,281 |             |   | $      | 1,075,600   |         |         | $      | 33,879 |   |   | $ | (390 | ) |   | $ | 4,164,370 |   |
|                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| Depreciation and amortization              |      | $        | 226,374   |             |   | $      | 53,535      |         |         | $      | 4,230 |   |   | $ | — |   |   | $ | 284,139 |   |
| Interest charges and financing costs       |      |     | 133,518   |             |   |   | 29,623      |         |         |   | 3,497 |   |   |   | — |   |   |   | 166,638 |   |
| Income tax expense (benefit)               |      |     | 198,139   |             |   |   | 36,278      |         |         |   | (5,236 | ) |   |   | — |   |   |   | 229,181 |   |
| Net income                                 |      |     | 299,148   |             |   |   | 70,279      |         |         |   | 30,293 |   |   |   | — |   |   |   | 399,720 |   |
|                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| 2009                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| Operating revenues from external customers |      | $        | 2,678,578 |             |   | $      | 1,093,959   |         |         | $      | 35,772 |   |   | $ | — |   |   | $ | 3,808,309 |   |
| Intersegment revenues                      |      |     | 266       |             |   |   | 79          |         |         |   | — |   |   |   | (345 | ) |   |   | — |   |
| Total revenues                             |      | $        | 2,678,844 |             |   | $      | 1,094,038   |         |         | $      | 35,772 |   |   | $ | (345 | ) |   | $ | 3,808,309 |   |
|                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| Depreciation and amortization              |      | $        | 200,776   |             |   | $      | 50,795      |         |         | $      | 4,491 |   |   | $ | — |   |   | $ | 256,062 |   |
| Interest charges and financing costs       |      |     | 121,434   |             |   |   | 25,242      |         |         |   | 1,084 |   |   |   | — |   |   |   | 147,760 |   |
| Income tax expense (benefit)               |      |     | 123,047   |             |   |   | 57,375      |         |         |   | (10,017 | ) |   |   | — |   |   |   | 170,405 |   |
| Net income                                 |      |     | 242,265   |             |   |   | 67,288      |         |         |   | 13,767 |   |   |   | — |   |   |   | 323,320 |   |
|                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| 2008                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| Operating revenues from external customers |      | $        | 2,982,929 |             |   | $      | 1,373,732   |         |         | $      | 36,383 |   |   | $ | — |   |   | $ | 4,393,044 |   |
| Intersegment revenues                      |      |     | 229       |             |   |   | 100         |         |         |   | — |   |   |   | (329 | ) |   |   | — |   |
| Total revenues                             |      | $        | 2,983,158 |             |   | $      | 1,373,832   |         |         | $      | 36,383 |   |   | $ | (329 | ) |   | $ | 4,393,044 |   |
|                                       |      |     |      |             |   |   |        |         |         |   |   |   |   |   |   |   |   |   |   |   |
| Depreciation and amortization              |      | $        | 190,544   |             |   | $      | 55,638      |         |         | $      | 6,202 |   |   | $ | — |   |   | $ | 252,384 |   |
| Interest charges and financing costs       |      |     | 110,263   |             |   |   | 25,505      |         |         |   | 279 |   |   |   | — |   |   |   | 136,047 |   |
| Income tax expense (benefit)               |      |     | 132,315   |             |   |   | 53,075      |         |         |   | (18,762 | ) |   |   | — |   |   |   | 166,628 |   |
| Net income                                 |      |     | 230,417   |             |   |   | 87,505      |         |         |   | 21,874 |   |   |   | — |   |   |   | 339,796 |   |

----

Index

| (Thousands of Dollars)                                   |   | 2010   |    |   | 2009   |   |    | 2008   |   |
|--------------------------------------------------------------------|--------|--------|---------|--------|--------|--------|---------|--------|--------|
| Operating revenues:                                                |   |   |    |   |   |   |    |   |   |
| Electric                                                           |   | $      | 9,428   |   |   | $      | 7,751   |   |   | $ | 38,625 |   |
| Other                                                              |   |   | 3,331   |   |   |   | 4,441   |   |   |   | 4,459 |   |
| Operating expenses:                                                |   |   |    |   |   |   |    |   |   |   |   |   |
| Purchased power                                                    |   |   | 6,805   |   |   |   | 5,976   |   |   |   | 7,000 |   |
| Other operating expenses — paid to Xcel Energy Services Inc. |   |   | 307,136 |   |   |   | 295,934 |   |   |   | 285,423 |   |
| Interest expense                                                   |   |   | 104     |   |   |   | 586     |   |   |   | 1,361 |   |

|                              |   | 2010       |   |   | 2009     |   |
|-----------------------------------|--------|------------|--------|--------|----------|--------|
|                              |   | Accounts   |   |   | Accounts |   |   | Accounts |   |   | Accounts |   |
| (Thousands of Dollars)  |   | Receivable |   |   | Payable  |   |   | Receivable |   |   | Payable |   |
| NSP-Minnesota                     |   | $          | 6,674  |   |     | $      | — |   |   | $ | 15,789 |   |   | $ | — |   |
| NSP-Wisconsin                     |   |       | 164    |   |     |   | — |   |   |   | 30 |   |   |   | — |   |
| SPS                               |   |       | 2,606  |   |     |   | — |   |   |   | — |   |   |   | 239 |   |
| Other subsidiaries of Xcel Energy |   |       | 11,598 |   |     |   | 28,270 |   |   |   | 17,577 |   |   |   | 40,519 |   |
|                              |   | $          | 21,042 |   |     | $      | 28,270 |   |   | $ | 33,396 |   |   | $ | 40,758 |   |

|                   |   | Quarter Ended  |      |
|------------------------|--------|----------------|-----------|
| (Thousands of Dollars) |   | March 31, 2010 |      |   | June 30, 2010 |   |   | Sept. 30, 2010 |   |   | Dec. 31, 2010 |   |
| Operating revenues     |   | $              | 1,202,697 |   |   | $ | 947,296 |   |   | $ | 954,970 |   |   | $ | 1,059,407 |   |
| Operating income       |   |           | 201,078   |   |   |   | 156,677 |   |   |   | 243,055 |   |   |   | 154,242 |   |
| Net income             |   |           | 84,250    |   |   |   | 77,685 |   |   |   | 158,091 |   |   |   | 79,694 |   |
|                   |   |           |      |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                   |   | Quarter Ended  |      |
| (Thousands of Dollars) |   | March 31, 2009 |      |   | June 30, 2009 |   |   | Sept. 30, 2009 |   |   | Dec. 31, 2009 |   |
| Operating revenues     |   | $              | 1,002,478 |   |   | $ | 769,093 |   |   | $ | 887,960 |   |   | $ | 1,148,778 |   |
| Operating income       |   |           | 141,983   |   |   |   | 116,150 |   |   |   | 169,832 |   |   |   | 167,706 |   |
| Net income             |   |           | 78,288    |   |   |   | 60,547 |   |   |   | 91,224 |   |   |   | 93,261 |   |

----

Index

| (Thousands of Dollars) |   |   |    |
|----------------------------------|--------|--------|---------|
| Assets acquired                  |   |   |    |
| Inventory                        |   | $      | 3,834   |   |
| Property, plant and equipment    |   |   | 735,916 |   |
| Total assets acquired            |   |   | 739,750 |   |
|                             |   |   |    |   |
| Liabilities assumed              |   |   |    |   |
| Accrued expenses                 |   |   | 7,255   |   |
| Total liabilities assumed        |   |   | 7,255   |   |
|                             |   |   |    |   |
| Net assets acquired              |   | $      | 732,495 |   |

Item 9 — Changes in and Disagreements With 

Item 9A — Controls and Procedures

----

Index

Item 9B — Other Information

PART III

Item 10 — Directors, Executive Officers and Corporate Governance

Item 11 — Executive Compensation

Item 12 — Security Ownership of Certain Beneficial Owners and Management 

Item 13 — Certain Relationships and Related Transactions, and Director Independence

Item 14 — Principal Accountant Fees and Services

----

Index

PART IV

Item 15 — Exhibits, Financial Statement Schedules

| 1. | Consolidated Financial Statements: |
|----|------------------------------------|

|   | Management Report on Internal Controls — For the year ended Dec. 31, 2010. |
|--------|---------------------------------------------------------------------------------------|

|   | Report of Independent Registered Public Accounting Firm — For the years ended Dec. 31, 2010, 2009 and 2008. |
|--------|------------------------------------------------------------------------------------------------------------------------|

|   | Consolidated Statements of Income — For the three years ended Dec. 31, 2010, 2009 and 2008. |
|--------|--------------------------------------------------------------------------------------------------------|

|   | Consolidated Statements of Cash Flows — For the three years ended Dec. 31, 2010, 2009 and 2008. |
|--------|------------------------------------------------------------------------------------------------------------|

|   | Consolidated Balance Sheets — As of Dec. 31, 2010 and 2009. |
|--------|------------------------------------------------------------------------|

| 2. | Schedule II — Valuation and Qualifying Accounts and Reserves for the years ended Dec. 31, 2010, 2009 and 2008. |
|----|---------------------------------------------------------------------------------------------------------------------------|

| 3. | Exhibits |
|----|----------|

|    | *Indicates incorporation by reference                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|    | +Executive Compensation Arrangements and Benefit Plans Covering Executive Officers and Directors                                                                                                                                                                                                                                                                                                                                                                |
|    | t   Certain portions of this agreement have been omitted pursuant to a request for confidential treatment and have been filed separately with the SEC.                                                                                                                                                                                                                                                                                           |
|    |                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| 2.01* t | Purchase and Sale Agreement by and between Riverside Energy Center, LLC and Calpine Development Holdings, Inc., as Sellers, and PSCo, as Purchaser, dated as of April 2, 2010 (excluding certain schedules and exhibits referred to in the agreement, as amended, which the Registrant agrees to furnish supplemental to the SEC upon request).  (Exhibit 2.01 to Form 10-Q of Xcel Energy (file no. 001-03034) for the quarter ended June 30, 2010). |
| 3.01*   | Amended and Restated Articles of Incorporation dated July 15, 1998 (Form 10-K, Dec. 31, 1998, Exhibit 3(a)(1)).                                                                                                                                                                                                                                                                                                                             |
| 3.02*   | By-laws dated Nov. 20, 1997 (Form 10-K, Dec. 31, 1997, Exhibit 3(b)(1)).                                                                                                                                                                                                                                                                                                                                                                    |
| 4.01*   | Indenture, dated as of Oct. 1, 1993, between PSCo and Morgan Guaranty Trust Company of New York, as trustee,providing for the issuance of First Collateral Trust Bonds (Form 10-Q, Sept. 30, 1993 — Exhibit 4(a)).                                                                                                                                                                                                                    |
| 4.02*   | Indentures supplemental to Indenture dated as of Oct. 1, 1993, between PSCo and Morgan Guaranty Trust Company of New York, as trustee,:                                                                                                                                                                                                                                                                                                                    |

| Dated as of |   | Previous Filing:Form; Date orfile no. |   | ExhibitNo. |   |
|-----------------------|--------|-----------------------------------------------------------|--------|------------|--------|
|                  |   |                                                      |   |       |   |
| Nov. 1, 1993     |   | S-3, (33-51167)                                           |   | 4(b)(2)    |   |
| Jan. 1, 1994     |   | 10-K, 1993                                                |   | 4(b)(3)    |   |
| Sept. 2, 1994         |   | 8-K, September 1994                                  |   | 4(b)       |   |
| May 1, 1996      |   | 10-Q, June 30, 1996                                  |   | 4(b)       |   |
| Nov. 1, 1996     |   | 10-K, 1996 (001-03280)                                    |   | 4(b)(3)    |   |
| Feb. 1, 1997     |   | 10-Q, March 31, 1997 (001-03280)                     |   | 4(a)       |   |
| April 1, 1998    |   | 10-Q, March 31, 1998 (001-03280)                     |   | 4(b)       |   |
| Aug. 15, 2002    |   | 10-Q, Sept. 30, 2002 (001-03280)                          |   | 4.03       |   |
| Sept. 1, 2002         |   | 8-K, Sept. 18, 2002(001-03280)                            |   | 4.01       |   |
| Sept. 15, 2002        |   | 10-Q, Sept. 30, 2002(001-03280)                           |   | 4.04       |   |
| March 1, 2003    |   | S-3, April 14, 2003 (333-104504)                     |   | 4(b)(3)    |   |
| April 1, 2003    |   | 10-Q May 15, 2003 (001-03280)                        |   | 4.02       |   |
| May 1, 2003      |   | S-4, June 11, 2003 (333-106011)                      |   | 4.9        |   |
| Sept. 1, 2003         |   | 8-K, Sept. 2, 2003 (001-03280)                            |   | 4.02       |   |
| Sept. 15, 2003        |   | Xcel 10-K, March 15, 2004 (001-03034)                |   | 4.100      |   |
| Aug. 1, 2005     |   | PSCo 8-K, Aug. 18, 2005 (001-03280)                  |   | 4.02       |   |
| Aug. 1, 2007     |   | PSCo 8-K, Aug. 14, 2007 (001-03280)                  |   | 4.01       |   |
| Nov. 1, 2010          |   | PSCo 8-K, Nov. 8, 2010 (001-03280)                        |   | 4.01       |   |

| 4.03* | Indenture dated July 1, 1999, between PSCo and The Bank of New York, providing for the issuance of Senior Debt Securities and Supplemental Indenture dated July 15, 1999, between PSCo and The Bank of New York (Exhibits 4.1 and 4.2 to Form 8-K (file no. 001-03280) dated July 13, 1999). |
|-------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

Index

| 4.04*   | Financing Agreement between Adams County, Colorado and PSCo, dated as of Aug. 1, 2005 relating to $129,500,000 Adams County, Colorado Pollution Control Refunding Revenue Bonds, 2005 Series A (Exhibit 4.01 to PSCo Current Report on Form 8-K, dated Aug. 18, 2005, file number 001-3280).                                                                                                              |
|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 4.05*   | Supplemental Indenture, dated Aug. 1, 2007, between PSCo and U.S. Bank Trust NA, as successor Trustee (Exhibit 4.01 to PSCo Form 8-K (file no 001-3280) dated Aug. 14, 2007).                                                                                                                                                                                                                                  |
| 4.06*   | Supplemental Indenture dated as of Aug. 1, 2008, between PSCo and U.S. Bank Trust NA, as successor Trustee, creating $300,000,000 principal amount of 5.80 percent First Mortgage Bonds, Series No. 18 due 2018 and $300,000,000 principal amount of 6.50 percent First Mortgage Bonds, Series No. 19 due 2038 (Exhibit 4.01 of Form 8-K of PSCo dated Aug. 6, 2008 (file no. 001-03280)). |
| 4.07*   | Supplemental Indenture dated as of May 1, 2009 between PSCo and U.S. Bank Trust NA, as successor Trustee, creating $400,000,000 principal amount of 5.125 percent First Mortgage Bonds, Series No. 20 due 2019 (Exhibit 4.01 of Form 8-K of PSCo dated May 28, 2009 (file no. 001-03280)).                                                                                                           |
| 4.08*   | Supplemental Indenture dated as of Nov. 1, 2010 between PSCo and U.S. Bank Trust NA, as successor Trustee, creating $400,000,000 principal amount of 3.200 percent First Mortgage Bonds, Series No. 21 due 2020 (Exhibit 4.01 of Form 8-K of PSCo dated Nov. 16, 2010 (file no. 001-03280)).                                                                                                                   |
| 10.01*+ | Xcel Energy Omnibus Incentive Plan (Exhibit A to Form DEF-14A (file no. 001-03034) filed Aug. 29, 2000).                                                                                                                                                                                                                                                                                                            |
| 10.02*+ | Xcel Energy Non-Qualified Pension Plan (2009 Restatement) (Exhibit 10.02 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008).                                                                                                                                                                                                                                                        |
| 10.03*+ | Amended and Restated Executive Long-Term Incentive Award Stock Plan (Exhibit 10.02 to NSP-Minnesota Form 10-Q (file no. 001-03034) for the quarter ended March 31, 1998).                                                                                                                                                                                                                                           |
| 10.04*+ | New Century Energies Omnibus Incentive Plan (Exhibit A to New Century Energies, Inc. Form DEF 14A (file no. 001-12927) filed March 26, 1998).                                                                                                                                                                                                                                                                  |
| 10.05*+ | Xcel Energy Senior Executive Severance Policy (2009 Amendment and Restatement) (Exhibit 10.05 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008).                                                                                                                                                                                                                                   |
| 10.06*+ | Stock Equivalent Plan for Non-Employee Directors of Xcel Energy as amended and restated Jan. 1, 2009 (Exhibit 10.06 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008.                                                                                                                                                                                                         |
| 10.07*+ | Xcel Energy Nonqualified Deferred Compensation Plan as amended and restated Jan. 1, 2009 (Exhibit 10.07 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008).                                                                                                                                                                                                                    |
| 10.08*+ | Xcel Energy Non-employee Directors’ Deferred Compensation Plan as amended and restated on Jan. 1, 2009 (Exhibit 10.08 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008).                                                                                                                                                                                                |
| 10.09*+ | Form of Services Agreement between Xcel Energy Services Inc. and utility companies (Exhibit H-1 to Form U5B (file no. 001-03034) dated Nov. 16, 2000).                                                                                                                                                                                                                                                         |
| 10.10*+ | Xcel Energy Omnibus Incentive Plan Form of Restricted Stock Unit Agreement (Exhibit 10.05 to Xcel Energy Form 10-Q (file no. 001-03034) dated June 30, 2005).                                                                                                                                                                                                                                                  |
| 10.11*+ | Xcel Energy Omnibus Incentive Plan Form of Performance Share Agreement (Exhibit 10.04 to Xcel Energy Form 10-Q (file no. 001-03034) dated June 30, 2005).                                                                                                                                                                                                                                                      |
| 10.12*+ | Xcel Energy Omnibus Incentive Plan Form of Restricted Stock Unit Agreement (Exhibit 10.07 to Xcel Energy Form 10-Q (file no. 001-03034) dated June 30, 2005).                                                                                                                                                                                                                                                  |
| 10.13*+ | Xcel Energy Omnibus 2005 Incentive Plan (Appendix B to Exhibit 14A, Definitive Proxy Statement of Xcel Energy Form (file no. 001-03034) dated April 11, 2005).                                                                                                                                                                                                                                                      |
| 10.14*+ | Xcel Energy Executive Annual Incentive Award Plan (Appendix C to Exhibit 14A, Definitive Proxy Statement of Xcel Energy Form (file no. 001-03034) dated April 11, 2005).                                                                                                                                                                                                                                            |
| 10.15*+ | Xcel Energy Supplemental Executive Retirement Plan as amended and restated Jan. 1, 2009 (Exhibit 10.17 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2008).                                                                                                                                                                                                                     |
| 10.16*  | Amended and Restated Coal Supply Agreement entered into Oct. 1, 1984 but made effective as of Jan. 1, 1976 between PSCo and Amax Inc. on behalf of its division, Amax Coal Co. (Form 10-K (file no. 001-03280) Dec. 31, 1984 — Exhibit 10I(1)).                                                                                                                                 |
| 10.17*  | First Amendment to Amended and Restated Coal Supply Agreement entered into May 27, 1988 but made effective Jan. 1, 1988 between PSCo and Amax Coal Co. (Form 10-K (file no. 001-03280) Dec. 31, 1988 — Exhibit 10I(2)).                                                                                                                                                              |
| 10.18*  | Proposed Settlement Agreement excerpts, as filed with the CPUC (Exhibit 99.02 to Form 8-K (file no. 001-03034) dated Dec. 3, 2004).                                                                                                                                                                                                                                                                                 |
| 10.19*  | Settlement Agreement among PSCo and Concerned Environmental and Community Parties, dated Dec. 3, 2004 (Exhibit 99.03 to Form 8-K (file no. 001-03034) dated Dec. 3, 2004).                                                                                                                                                                                                                                     |
| 10.20*  | Amendment dated as of April 13, 2009 to the PSCo Credit Agreement dated as of Dec. 14, 2006 (Exhibit 10.03 to Form 10-Q of Xcel Energy (file no. 001-03034) for the quarter ended June. 30, 2009).                                                                                                                                                                                                   |
| 10.21*  | Credit Agreement dated Dec. 14, 2006 between PSCo and various lenders (Exhibit 10.03 to Form 10-Q of Xcel Energy (file no. 001-03034) for the quarter ended Sept. 30, 2009).                                                                                                                                                                                                                              |
| 10.22*+ | Amendment dated Aug. 26, 2009 to the Xcel Energy Senior Executive Severance and Change-in-Control Policy (Exhibit 10.06 to Form 10-Q of Xcel Energy (file no. 001-03034) for the quarter ended Sept. 30, 2009).                                                                                                                                                                                           |

----

Index

| 10.23*+ | Xcel Energy Executive Annual Incentive Award Plan Form of Restricted Stock Agreement (Exhibit 10.08 to Form 10-Q of Xcel Energy (file no. 001-03034) for the quarter ended Sept. 30, 2009).                               |
|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 10.24*+ | Xcel Energy 2010 Executive Annual Discretionary Award Plan (Exhibit 10.24 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2009).                                                                  |
| 10.25*+ | Xcel Energy Executive Annual Incentive Award Plan (as amended and restated effective Feb. 17, 2010) (incorporated by reference to Appendix A to Schedule 14A, Definitive Proxy Statement to Xcel Energy (file no. 001-03034) dated April 6, 2010). |
| 10.26*+ | Xcel Energy 2005 Long-Term Incentive Plan (as amended and restated effective Feb. 17, 2010) (incorporated by reference to Appendix B to Schedule 14A, Definitive Proxy Statement to Xcel Energy (file no. 001-03034) dated April 6, 2010).         |
| 10.27*+ | Xcel Energy 2010 Executive Annual Discretionary Award Plan (as amended and restated effective Dec. 15, 2010) (Exhibit 10.23 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2010).           |
| 10.28*+ | Xcel Energy 2005 Long-Term Incentive Plan Form of Bonus Stock Agreement (Exhibit 10.24 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2010).                                           |
| 10.29*+ | Xcel Energy 2005 Long-Term Incentive Plan Form of Performance Share Agreement (Exhibit 10.25 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2010).                                               |
| 10.30*+ | Xcel Energy 2005 Long-Term Incentive Plan Form of Restricted Stock Unit Agreement (Exhibit 10.26 to Form 10-K of Xcel Energy (file no. 001-03034) for the year ended Dec. 31, 2010).                                           |
| 12.01   | Statement of Computation of Ratio of Earnings to Fixed Charges.                                                                                                                                                                                    |
| 23.01   | Consent of Independent Registered Public Accounting Firm.                                                                                                                                                                                          |
| 31.01   | Principal Executive Officer’s certification pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                              |
| 31.02   | Principal Financial Officer’s certification pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.                                                                              |
| 32.01   | Certification pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.                                                                                                                  |
| 99.01   | Statement pursuant to Private Securities Litigation Reform Act of 1995.                                                                                                                                                                            |

----

Index

|                                  |       |   |      | Additions  |         |       |         |       |       |   |   |
|---------------------------------------|------------|--------|-----------|------------|--------------|------------|--------------|------------|------------|--------|--------|
|                                  |       |   |      | Charged to |         | Charged to |         | Deductions |       |   |   |
|                                  | Balance at |   | costs and |       | other        |       | from         |       | Balance at |   |
|                                  | Jan. 1     |   | expenses  |       | accounts (a) |       | reserves (b) |       | Dec. 31    |   |
| Reserve deducted from related assets: |       |   |      |       |         |       |         |       |       |   |   |   |   |   |   |
| Allowance for bad debts:              |       |   |      |       |         |       |         |       |       |   |   |   |   |   |   |
| 2010                                  |       | $      | 24,149    |       |         | $          | 21,571       |       |       | $      | 7,192  |   |   | $ | 28,858 |   |   | $ | 24,054 |   |
| 2009                                  |       |   | 29,195    |       |         |       | 21,189       |       |       |   | 14,364 |   |   |   | 40,599 |   |   |   | 24,149 |   |
| 2008                                  |       |   | 23,301    |       |         |       | 28,372       |       |       |   | 8,146  |   |   |   | 30,624 |   |   |   | 29,195 |   |

| (a) Recovery of amounts previously written off.  |
|-------------------------------------------------------|
| (b) Principally bad debts written off or transferred. |

----

Index

SIGNATURES

|   | PUBLIC SERVICE COMPANY OF COLORADO                   |
|--------|------------------------------------------------------|
|   |                                                 |
|   | /s/ DAVID M. SPARBY                                  |
|   | David M. Sparby                                      |
|   | Vice President, Chief Financial Officer and Director |
|   | (Principal Financial Officer)                        |

| /s/ DAVID L. EVES                               |   | /s/ RICHARD C. KELLY                                 |
|-------------------------------------------------|--------|------------------------------------------------------|
| David L. Eves                                   |   | Richard C. Kelly                                     |
| President, Chief Executive Officer and Director |   | Chairman and Director                                |
| (Principal Executive Officer)                   |   |                                                 |
|                                            |   |                                                 |
| /s/ TERESA S. MADDEN                            |   | /s/ DAVID M. SPARBY                                  |
| Teresa S. Madden                                |   | David M. Sparby                                      |
| Vice President and Controller                   |   | Vice President, Chief Financial Officer and Director |
| (Principal Accounting Officer)                  |   | (Principal Financial Officer)                        |
|                                            |   |                                                 |
| /s/ BENJAMIN G.S. FOWKE III                     |   |                                                 |
| Benjamin G.S. Fowke III                         |   |                                                 |
| Vice President and Director                     |   |                                                 |

----