i

TO: Distribution Transformers Negotiation Committee

FROM: The Department of Energy

DATE: Tuesday, 20 September 2011

RE: Updates to the Analytical Methodology since the Preliminary Analysis

As requested by the Negotiation Committee, Lawrence Berkeley National Laboratory and Navigant have 

prepared a summary of changes made to the preliminary analysis since its publication in March of 2011. 

The details, by chapter, are listed below.
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TABLE OF CONTENTS

1. Chapter 3 – Market and Technology Assessment ................................................................................1

1.1. (no changes)..................................................................................................................................1

2. Chapter 4 – Screening Analysis.............................................................................................................1

2.1. (no changes)..................................................................................................................................1

3. Chapter 5 – Engineering Analysis..........................................................................................................1

3.1. Additional Design Line ..................................................................................................................1

3.2. Additional Design Option Combinations (DOCs)...........................................................................2

3.3. Conductor Pricing..........................................................................................................................2

3.4. Terminology ..................................................................................................................................2

3.5. Small Adjustments to Tank Dimensions and Oil Quantities .........................................................3

3.6. Large Amorphous Labor Hours.....................................................................................................3

3.7. Shipping.........................................................................................................................................3

3.8. Material Prices..............................................................................................................................3

3.9. Impedance ....................................................................................................................................4

4. Chapter 6 – Markups Analysis...............................................................................................................5

5. Chapter 7 – Energy Use and End-Use Loan Characterization ...............................................................7

6. Chapter 8 – Life-Cycle Cost and Payback Period Analysis.....................................................................7

7. Chapter 9 – Shipments Analysis............................................................................................................9

8. Chapter 10 – National Impacts Analysis .............................................................................................10

8.1. Mapping of Draft Efficiency Levels to Draft Trial Standard Levels..............................................11

8.1.1. Mapping of dELs to dTSL for Liquid-Immersed Transformers ............................................12

8.1.2. Mapping of dELs to dTSL for Low-Voltage Dry-Type Transformers....................................12

8.1.3. Mapping of dELs to dTSL for Medium Voltage Dry-Type Transformers.............................12

8.2. Scaling of Draft Trial Standard Levels across Equipment Classes...............................................13

8.2.1. Proposed Scaling of Efficiencies for Liquid-Immersed Transformers.................................14

8.2.2. Proposed Scaling of Efficiencies for Low-Voltage Dry-Type Transformers.........................16

8.2.1. Proposed Scaling of Efficiencies for Medium-Voltage Dry-Type Transformers..................18

9. Chapter 11 – Life-Cycle Cost Subgroups Analysis...............................................................................24

9.1. Rural Cooperatives and Municipal Utilities.................................................................................24

9.2. Vault Installed Transformers.......................................................................................................25
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LIST OF TABLES

Table 3.1 Design Option Combinations from Design Line 1 (Preliminary Analysis)................................2

Table 3.2 Design Option Combinations from Design Line 1 (NOPR).......................................................2

Table 3.3 Normal Impedance Ranges for Liquid-Immersed Transformers.............................................4

Table 3.4 Normal Impedance Ranges for Dry-Type Transformers..........................................................5

Table 4.1 Summary of Changes and Key Issues to the Markups Analysis...............................................5

Table 5.1 Summary of Changes and Key Issues to the Energy Use Analysis...........................................7

Table 6.1 Summary of Changes and Key Issues to the Life-Cycle Cost and Payback Period Analysis.....7

Table 7.1 Summary of Changes and Key Issues to the Shipments Analysis............................................9

Table 8.1 Summary of Changes and Key Issues to the National Impact Analysis.................................10

Table 8.2 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for Liquid-Immersed 

Transformers .........................................................................................................................12

Table 8.3 Proposed Efficiencies for Draft Trial Standard Levels for Liquid-Immersed Transformers...12

Table 8.4 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for Low-Voltage Dry-Type 

Transformers .........................................................................................................................12

Table 8.5 Proposed Efficiencies for Draft Trial Standard Levels for Low-Voltage Dry-Type 

Transformers .........................................................................................................................12

Table 8.6 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for Medium-Voltage DryType Transformers.................................................................................................................13

Table 8.7 Proposed Draft Trial Standard Levels for Medium-Voltage Dry-Type Transformers............13

Table 8.8 Scaled Efficiencies for Single Phase Liquid-Immersed Transformers....................................14

Table 8.9 Scaled Efficiencies for Three Phase Liquid-Immersed Transformers ....................................15

Table 8.10 Scaled Efficiencies for Single Phase Low-Voltage Dry-Type Transformers............................16

Table 8.11 Scaled Efficiencies for Three Phase Low-Voltage Dry-Type Transformers............................17

Table 8.12 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 20-45BIL......18

Table 8.13 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 20-45BIL......19

Table 8.14 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 46-95BIL......20

Table 8.15 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 46-95BIL......21

Table 8.16 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 96-150BIL....22

Table 8.17 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 96-150BIL....23

LIST OF FIGURES

Figure 1 An example of the changes from the preliminary analysis CSLs to the NOPR dELs is shown 

below for design line 9. .............................................................................................................3

Figure 2 Scaled Efficiency Curve for Single Phase Liquid-Immersed Transformers..............................15

Figure 3 Scaled Efficiency Curve for Single Phase Liquid-Immersed Transformers..............................16

Figure 4 Scaled Efficiency Curve for Single Phase Low-Voltage Dry-Type Transformers......................17

Figure 5 Scaled Efficiency Curves for Three Phase Low-Voltage Dry-Type Transformers ....................18
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Figure 6 Scaled Efficiency Curves for Single Phase Medium-Voltage Dry-Type Transformers 

20-45BIL...................................................................................................................................19

Figure 7 Scaled Efficiency Curves for Three Phase Medium-Voltage Dry-Type Transformers 

20-45BIL...................................................................................................................................20

Figure 8 Scaled Efficiency Curves Single Phase Medium-Voltage Dry-Type Transformers 46-95BIL....21

Figure 9 Scaled Efficiency Curves Three Phase Medium-Voltage Dry-Type Transformers 46-95BIL ....22

Figure 10 Scaled Efficiency Curves Single Phase Medium-Voltage Dry-Type Transformers 96-150BIL..23

Figure 11 Scaled Efficiency Curves Three Phase Medium-Voltage Dry-Type Transformers 96-150BIL..24
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Updates to the Analytical Methodology since the Preliminary Analysis

1. Chapter 3 – Market and Technology Assessment

1.1. (no changes)

2. Chapter 4 – Screening Analysis

2.1. (no changes)

3. Chapter 5 – Engineering Analysis

3.1. Additional Design Line

In the preliminary analysis, DOE modeled the medium-voltage, dry-type transformer market 

using five design lines over three BIL ranges. Although the lower two BIL ranges (20-45 kV and 46-95 

kV) each had high (1500) and low (300) kVA representative units, the highest BIL level (≥96 kV) was 

covered by a single, high (2000) kVA representative unit. DOE received comments that it should 

analyze high BIL, low kVA units directly and opted to add a representative unit at 125 kV ( ≥96 kV 

class) and 300 kVA. The chart below illustrates relative placement of the representative units as they 

currently stand.

EC 6 EC 8 EC 10

20-45kV 46-95kV >96kV

15 -

30 -

45 -

75 -

112.5 -

150 -

225

300

500

750

1000

1500

2000

2500

Dry-Type, Medium Voltage, Three-Phase DL 9 DL 11 DL 10 DL 12

DL 13 (A & B)

Rep Unit

Rep Unit

Rep Unit

Rep Unit

Rep Unit

Rep Unit
2

3.2. Additional Design Option Combinations (DOCs)

Within a design line, DOE models several combinations of steel, conductor, transformer 

geometry (e.g. core, or shell) and core conductor (e.g. full miter, distributed gap) to represent what 

is commonly found in the market. It adjusts those DOCs continually to reflect market trends, such as

including more designs with partially or wholly aluminum windings and fewer with wholly copper 

windings. Chapter 5 of the technical support document (TSD) contains the details of the changes –

below is an example of how one design line changed following the preliminary analysis.

Table 3.1 Design Option Combinations from Design Line 1 (Preliminary Analysis)

Core Material High-Voltage 

Conductor

Low-Voltage 

Conductor Core Design Type

M5 Cu – wire Al – strip Shell – DG* Wound Core

M3 Al – wire Al – strip Shell – DG Wound Core

M3 Cu – wire Al – strip Shell – DG Wound Core

M2 Cu – wire Al – strip Shell – DG Wound Core

ZDMH Cu – wire Cu – strip Shell – DG Wound Core

SA1 (Amorphous) Cu – wire Cu – strip Shell – DG Wound Core

Table 3.2 Design Option Combinations from Design Line 1 (NOPR)

Core Material High-Voltage 

Conductor

Low-Voltage 

Conductor Core Design Type

M5 Cu – wire Al – strip Shell – DG* Wound Core

M3 Al – wire Al – strip Shell – DG Wound Core

M3 Cu – wire Al – strip Shell – DG Wound Core

M2 Al – wire Al – strip Shell – DG Wound Core

M2 Cu – wire Al – strip Shell – DG Wound Core

ZDMH Al – wire Al – strip Shell – DG Wound Core

ZDMH Cu – wire Cu – strip Shell – DG Wound Core

SA1 (Amorphous) Al – wire Al – strip Shell – DG Wound Core

SA1 (Amorphous) Cu – wire Cu – strip Shell – DG Wound Core

3.3. Conductor Pricing

Ordinarily, DOE develops materials prices by surveying manufacturers who regularly purchase 

those materials. Following the preliminary analysis, several parties suggested that copper and 

aluminum commodity volatility led to quickly changing prices for all sizes of conductor. 

Subsequently, DOE moved to a pricing model that applies a fixed processing cost to an index-derived 

commodity price for raw copper or aluminum. It believes this pricing methodology will both produce 

more current prices and permit DOE to update prices without burdening manufacturers with 

frequent data requests.

3.4. Terminology

In the preliminary analysis, DOE used the term “candidate standard level” (CSL) to refer to the 

progressively higher efficiency benchmarks within a design line. In the NOPR, DOE begins referring 

to those same things as “efficiency levels” (ELs). For the purposes of the negotiation proceedings, 
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DOE has labeled the engineering plots with “draft efficiency levels,” or dELs. It is combinations of 

these dELs or ELs that are packaged together into “trial standard levels”, or TSLs.

Figure 1 An example of the changes from the preliminary analysis CSLs to the NOPR dELs 

is shown below for design line 9. 

3.5. Small Adjustments to Tank Dimensions and Oil Quantities

DOE solicits feedback on engineering data during interviews with manufacturers and often 

makes small adjustments to design parameters where warranted. Following the preliminary 

analysis, DOE made minor adjustments to tank dimensions and oil quantities for certain designs.

3.6. Large Amorphous Labor Hours

DOE received feedback that large medium-voltage, dry-type units (Design Lines 10, 12, and 13B) 

may require additional labor when constructed with amorphous cores, and adjusted labor hours 

accordingly.

3.7. Shipping

To reflect current rates, DOE raised its calculated shipping cost from 22 to 28 cents per pound.

3.8. Material Prices

DOE populates each respective design line’s cost-efficiency space with a large number of designs 

of varying specifications. As time passes and the prices of the constituent materials fluctuate, DOE 
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has two options for updating the cost-efficiency cloud of points. The first method is to apply more 

recent material prices to existing designs. This can work well with a large number of designs, 

because those that were “suboptimal” with at previous material price levels can become “optimal” 

at the new ones. If conductor prices rise relative to core steel, for example, the designs that contain 

relatively less conductor at a given efficiency will be found to be more cost effective.

Even further accuracy can be gained by reoptiziming, or creating entirely new designs with the 

new material prices as inputs. DOE had reoptimized many, but not all, design option combinations 

for the preliminary analysis. Presently, all design lines have been optimized with respect to 2010 

materials prices.

3.9. Impedance

DOE revised its respective design line impedance ranges to align with those published under 10 

CFR 431.192 (see tables 1 and 2 below). This change affects a very small number of designs and does 

not substantively change the covered cost-efficiency space for any design lines.

Table 3.3 Normal Impedance Ranges for Liquid-Immersed Transformers

Single-phase transformers Three-phase transformers

kVA

Impedance

(%) kVA

Impedance

(%)

10 1.0–4.5 15 1.0–4.5

15 1.0–4.5 30 1.0–4.5

25 1.0–4.5 45 1.0–4.5

37.5 1.0–4.5 75 1.0–5.0

50 1.5–4.5 112.5 1.2–6.0

75 1.5–4.5 150 1.2–6.0

100 1.5–4.5 225 1.2–6.0

167 1.5–4.5 300 1.2–6.0

250 1.5–6.0 500 1.5–7.0

333 1.5–6.0 750 5.0–7.5

500 1.5–7.0 1000 5.0–7.5

667 5.0–7.5 1500 5.0–7.5

833 5.0–7.5 2000 5.0–7.5

2500 5.0–7.5
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Table 3.4 Normal Impedance Ranges for Dry-Type Transformers

Single-phase transformers Three-phase transformers

kVA

Impedance

(%) kVA

Impedance

(%)

15 1.5–6.0 15 1.5–6.0

25 1.5–6.0 30 1.5–6.0

37.5 1.5–6.0 45 1.5–6.0

50 1.5–6.0 75 1.5–6.0

75 2.0–7.0 112.5 1.5–6.0

100 2.0–7.0 150 1.5–6.0

167 2.5–8.0 225 3.0–7.0

250 3.5–8.0 300 3.0–7.0

333 3.5–8.0 500 4.5–8.0

500 3.5–8.0 750 5.0–8.0

667 5.0–8.0 1000 5.0–8.0

833 5.0–8.0 1500 5.0–8.0

2000 5.0–8.0

2500 5.0–8.0

4. Chapter 6 – Markups Analysis

The markups analysis (chapter 6) develops appropriate markups in the distribution chain to 

convert the estimates of manufacturer selling price derived in the engineering analysis to customer 

prices. In the preliminary analysis, DOE determined the distribution channels for distribution 

transformers, their shares of the market, and the markups associated with the main parties in the 

distribution chain, distributors, contractors and electric utilities. The following table lists the changes to 

the preliminary analysis.

Table 4.1 Summary of Changes and Key Issues to the Markups Analysis

Topic Preliminary Analysis Description Changes for Proposed Rule

Sales Tax The factor that accounts for sales tax, 

estimated to be 1.069

No change

Distributor 

Markup

Described in TSD 

Chapter 6 Section 

6.2

The manufacturer selling price for liquidtype distribution transformers have a 7%

markup, accounting for distributor 

markup. While the manufacturer selling 

prices for dry-type transformers include 

two price markups: a distributor markup 

The department eliminated the 7% 

distributor markup liquid-immersed for 

a fraction of cases to account for 

transformer sales that are from 

manufacturers directly to utilities. The 

fraction of cases is determined by the 
6

of 15% and a contractor materials 

markup of 10%. DOE based these 

markups (expressed as average 

multipliers) on RS Means Electrical Cost 

Data 2010

amount of electricity reportedly sold by 

IOUs in EIA’s Form 861, is 82%.

No change for dry-type transformers.

Labor and 

Equipment

Described in TSD 

Chapter 6 Section 

6.3

The labor cost required for installation, 

including unloading, uncrating, hauling 

within 200 feet of the loading dock, 

setting in place, connecting to the 

distribution network, and testing; 

estimated from RS Means 2010 at 1.43

Updated using RS Means 2011 to 1.47

Impact of 

Transformer 

Weight on 

Installation Costs

Described in TSD 

Chapter 6 Section 

6.3.2

None DOE derived the weight-versus-capacity 

relationship for typical transformers 

from the design data produced by the 

engineering analysis. It used the weightversus-capacity relationship to estimate 

the transformer weight corresponding 

to the transformer costs reported in RS 

Means. DOE estimated a scaling 

relationship between transformer 

weight and direct installation labor and 

equipment costs by fitting the 

correlation between weight and 

installation costs to a power- law 

equation.

Pole 

Replacement

Described in TSD 

Chapter 6 Section 

6.3.1

DOE included a pole-replacement cost 

function as a part of the installation cost 

equation for DL2, which covers polemounted transformers. Because not all 

transformer installations require a 

change-out of existing equipment even 

in the most extreme case, DOE assumed 

a maximum change-out fraction. DOE 

selected 25 percent as the maximum 

change-out fraction estimate based on 

stakeholder input from the 2007 final 

rule. This analysis assumed that a pole 

change-out cost of $2,000 occurs for up 

to 25 percent of pole-mounted 

transformers when the weight of the 

transformer exceeds 1,000 pounds. DOE 

also included a transformer pole support 

cost of $0.12/lb to account for the cost 

of a sturdier pole. 

The highest transformer weight at CSL 7 

from the LCC results is just over 700 lbs. 

Therefore, DOE believes that pole 

replacement would not be a factor for 

the representative capacity for design 

line 2. DOE acknowledges that there 

may be situations where pole changeouts may be necessary when 

transformers are replaced with the same 

size unit, but DOE has no information to 

estimate the fraction of installations that 

may be impacted

No change
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5. Chapter 7 – Energy Use and End-Use Load Characterization

The energy use and end-use load characterization analysis (chapter 7) produced energy use 

estimates and end-use load shapes for distribution transformers. The energy use estimates enabled 

evaluation of energy savings from the operation of distribution transformer equipment at various 

efficiency levels, while the end-use load characterization allowed evaluation of the impact on monthly 

and peak demand for electricity from the operation of transformers. The following table lists the 

changes to the preliminary analysis.

Table 5.1 Summary of Changes and Key Issues to the Energy Use Analysis

Topic Preliminary Analysis Description Changes for Proposed Rule

Joint Distribution 

Function

Described in TSD 

Chapter 7 Section 

7.2.1 & Appendix 

7A Section 7A.2.2

Load on an individual transformer 

correlates somewhat with system load, 

there is some correlation between 

transformer load losses and the price of 

electricity. To capture those 

correlations, DOE developed a statistical 

model based on hourly electric system 

load data, marginal hourly electric 

system production prices: a joint 

probability distribution (JPDF) between 

transformer and system load levels. 

Separate JPDFs were constructed for 

residential, and commercial and 

industrial customers.

For liquid-immersed transformers to

capture the differences in load profiles 

of commercial, and industrial customers. 

The JPDF for commercial and industrial 

customers has been separated into two 

distinct entities with one JPDF for 

commercial customers and one JPDF for 

industrial customers.

No change for dry-type transformers

6. Chapter 8 – Life-Cycle Cost and Payback Period Analysis

DOE conducts LCC and PBP analyses (chapter 8) to evaluate the economic impacts on individual 

customers of potential energy conservation standards for distribution transformers. The LCC is the total 

customer expense over the life of a product, consisting of purchase and installation costs plus operating 

costs (expenses for energy use, maintenance and repair). To compute the operating costs, DOE 

discounts future operating costs to the time of purchase and sums them over the lifetime of the 

product. The PBP is the estimated amount of time (in years) it takes customers to recover the increased 

purchase cost (including installation) of a more efficient product through lower operating costs. DOE 

calculates the PBP by dividing the change in purchase cost (normally higher) due to a more stringent 

standard by the change in average annual operating cost (normally lower) that results from the 

standard. The following table lists the changes to the preliminary analysis.

Table 6.1 Summary of Changes and Key Issues to the Life-Cycle Cost and Payback Period 

Analysis

Topic Preliminary Analysis Description Changes for Proposed Rule

Affecting Installed Costs
8

Equipment price

Derived by multiplying manufacturer 

selling price (from the engineering 

analysis) by distributor markup and 

contractor markup plus sales tax for drytype transformers. For liquid-immersed 

transformers, DOE used manufacturer 

selling price plus small distributor markup 

plus sales tax. Additional weigh related

costs were included for both types of 

transformers.

See Markups Analysis

Baseline and 

standard design 

selection

Described in TSD 

Chapter 8 Section 

8.3.1

The selection of baseline and standardcompliant transformers depended on 

customer behavior. For liquid-immersed 

transformers, the fraction of purchases 

evaluated was 75%, while for dry-type 

transformers, the fraction of evaluated 

purchases was 50% for small capacity 

medium voltage and 80% for largecapacity medium voltage

Based on stakeholder feedback and 

research DOE adjusted the percent of 

evaluators to: 50% for liquid-immersed 

transformers, 2% for low-voltage drytype transformers, and 10 and 20% for 

low and high capacity medium voltage 

dry-type transformers respectively.

Affecting Operating Costs

Transformer 

loading

Loading depended on customer and 

transformer characteristics. No change

Load growth 1% per year for liquid-immersed and 0% 

per year for dry-type transformers. No change

Power factor Assumed to be unity. No change.

Annual energy use 

and demand

Derived from a statistical hourly load 

simulation for liquid-immersed 

transformers, and estimated from the 

1992 and 1995 Commercial Building 

Energy Consumption Survey data for dry- See Energy Use Analysis

type transformers using factors derived 

from hourly load data. Load losses varied 

as the square of the load and were equal 

to rated load losses at 100% loading.

Electricity costs

Derived from tariff-based and hourly 

based electricity prices. Capacity costs 

provided extra value for reducing losses 

at peak. 

No change

Electricity price 

trend

Obtained from Annual Energy Outlook 

2010 (AEO2010).

Updated to Annual Energy Outlook 2011

(AEO2011).

Maintenance cost Annual maintenance cost did not vary as 

a function of efficiency. No change.

Compliance date Assumed to be 2016. No change.
9

Discount rates

Described in TSD 

Chapter 8 Section 

8.3.8

Mean real discount rates ranged from 

4.0% for owners of pole-mounted, liquidimmersed transformers to 5.1% for drytype transformer owners.

The mean real discount rates were 

adjusted to 3.7% for owners of liquidimmersed transformers and 4.6% for drytype transformers.

Lifetime

Distribution of lifetimes, with mean 

lifetime for both liquid and dry-type 

transformers assumed to be 32 years.*

No change.

* Source: ORNL -6847, Determination Analysis of Energy Conservation Standards for Distribution Transformers, 1996

7. Chapter 9 – Shipments Analysis

DOE developed a shipments model to predict shipments of distribution transformers (chapter 

8). The shipments model provides an estimate of the rate at which an in-service stock of existing 

transformers may be replaced by new, more efficient transformers after the enactment of an energy 

conservation standard. The core of the shipments analysis is an accounting model that DOE developed 

to simulate how existing and future purchases are incorporated into an in-service stock of aging 

transformers that are gradually replaced. In estimating the effects of potential new standard levels on 

product shipments, the model accounts for the combined effects on the purchase decision of increases 

in purchase price, decreases in annual operating costs, and consumer income. The following table lists 

the changes to the preliminary analysis. The following table lists the changes to the preliminary analysis.

Table 7.1 Summary of Changes and Key Issues to the Shipments Analysis

Topic Preliminary Analysis Description Changes for Proposed Rule

Shipments data Third-party expert (HVOLT) for 

2009.

No change.

Shipments forecast 2016-2044: Based on AEO 2010. Updated to 

Dry-type/liquidimmersed market 

shares

AEO 2011

Based on EIA’s electricity sales data 

and AEO2010

Updated to 

.

Regular 

replacement 

market

AEO 2011

Based on a survival function 

constructed from a Weibull 

distribution function normalized to 

produce a 32-year mean lifetime. 

Source: ORNL 6804/R1, The 

Feasibility of Replacing or 

Upgrading Utility Distribution 

Transformers During Routine 

Maintenance

No change.

, page D-1.
10

Elasticities, liquidimmersedFor liquid-immersed transformers:

• Low: 0.00

• Medium: -0.04

• High: -0.20

For dry-type transformers:

• Low: 0.00

• Medium: -0.02

• High: -0.20

No change.

8. Chapter 10 – National Impacts Analysis

DOE’s NIA assessed the national energy savings (NES) and the national NPV of total customer 

costs and savings that would be expected to result from amended standards at specific efficiency levels

(chapter 10). The following table lists the changes to the preliminary analysis.

Table 8.1 Summary of Changes and Key Issues to the National Impact Analysis

Topic Preliminary Analysis Description Changes for Proposed Rule

Shipments Annual shipments from shipments 

model.

No change.

Compliance date of 

standard

2016. No change.

Base case 

efficiencies

Constant efficiency through 2044. 

Equal to weighted-average 

efficiency in 2016.

No change.

Standards case 

efficiencies

Constant efficiency at the specified 

standard level from 2016 to 2044.

No change.

Annual energy 

consumption per 

unit

Average rated transformer losses 

are obtained from the LCC analysis, 

and are then scaled for different 

size categories, weighted by size 

market share, and adjusted for 

transformer loading (also obtained 

from the LCC analysis).

No change.

Total installed cost 

per unit

Weighted-average values as a 

function of efficiency level (from 

LCC analysis).

No change.

Electricity expense 

per unit

Energy and capacity savings for the 

two types of transformer losses are 

each multiplied by the 

corresponding average marginal 

costs for capacity and energy, 

respectively, for the two types of 

losses (marginal costs are from the 

LCC analysis).

No change.
11

Escalation of 

electricity prices

AEO 2010 Updated the escalation of electricity 

prices forecast using 

forecasts (to 2035) and 

extrapolation for 2044 and beyond.

Electricity site-tosource conversion

AEO 2011

Described in TSD 

Chapter 10 Section 

10.2.2.8

A time series conversion factor; 

includes electric generation, 

transmission, and distribution 

losses. Conversion varies yearly and 

is generated by DOE/EIA’s National 

Energy Modeling System (NEMS) 

program. 

Updated conversion factors from 

NEMS.

Discount rates 3% and 7% real discount rates 

mandated by OMB.

No change

Equipment Price 

Trend

Described in TSD 

Chapter 8 Section 

8.2.1.1 & Chapter 10 

Section 10.3.2.8

None DOE observed changes in the 

inflation-adjusted index of the PPI 

for electric power and specialty 

transformer manufacturing over 

1967-2010. These data show a longterm decline from 1975 to 2003, and 

then a steep increase since then. 

DOE believes that there is 

considerable uncertainty as to 

whether the recent trend has 

peaked, and would be followed by a 

return to the previous long-term 

declining trend, or whether the 

recent trend represents the 

beginning of a long-term rising trend 

due to global demand for 

distribution transformers and rising 

commodity costs for key transformer 

components. Given the uncertainty, 

DOE has chosen to use constant 

prices (2010 levels) for both its LCC 

and PBP analysis and the NIA. For the 

NIA, DOE also analyzed the 

sensitivity of results to alternative 

transformer price forecasts. DOE 

developed one forecast in which 

prices decline after 2010, and one in 

which prices rise.

Present year Equipment and operating costs are 

discounted to the year of 

equipment price data, 2010. 

No change 

8.1. Mapping of Draft Efficiency Levels to Draft Trial Standard Levels

The mapping of dEL to dTSL is expand in greater detail in chapter 10 section 10.2.2.2 and 10.2.2.3. 

The result of this mapping is presented in the tables below.
12

8.1.1. Mapping of dELs to dTSL for Liquid-Immersed Transformers

Table 8.2 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for LiquidImmersed Transformers

Design Line dTSL1 dTSL2 dTSL3 dTSL4 dTSL5

1 Liquid-Immersed, 50kVA, single-phase dEL1 dEL2 dEL3 dEL4 dEL7

2 Liquid-Immersed, 25kVA, single-phase dEL1 dEL2 dEL3 dEL4 dEL7

3 Liquid-Immersed, 500kVA, single-phase dEL2 dEL3 dEL4 dEL5 dEL7

4 Liquid-Immersed, 150kVA, three-phase dEL1 dEL2 dEL3 dEL4 dEL7

5 Liquid-Immersed, 1500kVA, three-phase dEL2 dEL3 dEL4 dEL5 dEL7

Table 8.3 Proposed Efficiencies for Draft Trial Standard Levels for Liquid-Immersed 

Transformers

Design 

Line Base

dTSL

1 2 3 4 5

1 99.08 99.16 99.22 99.25 99.31 99.50

2 98.91 99.00 99.07 99.11 99.18 99.46

3 99.42 99.51 99.54 99.57 99.61 99.73

4 99.08 99.16 99.22 99.25 99.31 99.60

5 99.42 99.51 99.54 99.57 99.61 99.69

8.1.2. Mapping of dELs to dTSL for Low-Voltage Dry-Type Transformers

Table 8.4 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for LowVoltage Dry-Type Transformers

Design Line dTSL1 dTSL2* dTSL3 dTSL4 dTSL5 dTSL6

6 LVDT, 25kVA, single-phase dEL2 dEL3* dEL3 dEL4 dEL5 dEL7

7 LVDT, 75kVA, three-phase dEL2 dEL3* dEL3 dEL4 dEL5 dEL7

8 LVDT, 300kVA, three-phase dEL3 dEL2* dEL4 dEL5 dEL6 dEL7

*NEMA Premium

Table 8.5 Proposed Efficiencies for Draft Trial Standard Levels for Low-Voltage Dry-Type 

Transformers

Design 

Line Base

TSL

1 2 3 4 5 6

6 98.00 98.47 98.60 98.80 98.93 99.44 98.00

7 98.00 98.47 98.60 98.80 98.93 99.44 98.00

8 98.60 99.14 99.25 99.32 99.44 99.58 98.60

8.1.3. Mapping of dELs to dTSL for Medium Voltage Dry-Type Transformers
13

Table 8.6 Mapping of Draft Efficiency Levels to Draft Trial Standard Levels for MediumVoltage Dry-Type Transformers

Design Line dTSL1 dTSL2 dTSL3 dTSL4 dTSL5

9 MVDT, 300kVA, three-phase, 45kV BIL dEL1 dEL2 dEL3 dEL4 dEL7

10 MVDT, 1500kVA, three-phase, 45kV BIL dEL2 dEL3 dEL4 dEL5 dEL7

11 MVDT, 300kVA, three-phase, 95kV BIL dEL1 dEL2 dEL3 dEL4 dEL7

12 MVDT, 1500kVA, three-phase, 95kV BIL dEL2 dEL3 dEL4 dEL5 dEL7

13A MVDT, 300kVA, three-phase, 125kV BIL dEL1 dEL2 dEL3 dEL4 dEL7

13B MVDT, 2000kVA, three-phase, 125kV BIL dEL2 dEL3 dEL4 dEL5 dEL7

Table 8.7 Proposed Draft Trial Standard Levels for Medium-Voltage Dry-Type 

Transformers

Design 

Line Base

TSL

1 2 3 4 5

9 98.82 98.99 99.12 99.28 99.38 99.59

10 99.22 99.40 99.50 99.53 99.60 99.67

11 98.67 98.81 98.94 99.06 99.13 99.50

12 99.12 99.30 99.39 99.46 99.53 99.65

13A 98.63 98.76 98.85 98.92 99.10 99.48

13B 99.15 99.31 99.38 99.43 99.49 99.58

8.2. Scaling of Draft Trial Standard Levels across Equipment Classes

Transformers are produced over a broad range of capacities, only a few of which are modeled 

explicitly in this analysis. The modeled designs are referred to as representative units. Any given 

equipment type includes 2-4 representative units at different capacity, or kVA values. DOE used a scaling 

relationship, or equation, to project the economic results from a given transformer design line to similar 

transformers of different sizes. This relationship is a key element in adjusting losses and costs from a 

representative transformer in the LCC to the distribution of transformer sizes incorporated in the 

calculation of NES and subject to potential standards. The Department uses the 0.75 scaling rule to 

scale the cost and efficiency results for the modeled kVA values to the full capacity range for each type, 

the 0.75 scaling rule is discussed in greater detail in chapter 5. This rule assumes that both the physical 

and cost characteristics are determined by the quantity of material required to build the transformer, 

and is approximately true. In practice, if the kVA-range over which cost and efficiency data are to be 

scaled is large, the 0.75 rule is less accurate. This manifests as kinks or angles in the curve of efficiency as 

a function of capacity for a given equipment type.

The Department has implemented a correction to the 0.75 scaling rule to produce smoother 

curves of efficiency vs. capacity. This correction adjusts the value of the exponent (the 0.75 of the 

scaling rule) so that the curve extrapolates correctly between any two representative units. 
14

The method use to calculate these efficiencies is described in detail in chapter 10 section 

10.2.2.1.

8.2.1. Proposed Scaling of Efficiencies for Liquid-Immersed Transformers

Table 8.8 Scaled Efficiencies for Single Phase Liquid-Immersed Transformers

TSL

kVA Base 1 2 3 4 5

10 98.62 98.74 98.83 98.88 98.97 99.25

15 98.76 98.86 98.95 98.99 99.07 99.32

DL2 25 98.91 99.00 99.07 99.11 99.18 99.46

37.5 99.01 99.10 99.16 99.19 99.26 99.48

DL1 50 99.08 99.16 99.22 99.25 99.31 99.50

75 99.17 99.24 99.29 99.32 99.38 99.55

100 99.23 99.29 99.33 99.37 99.42 99.58

167 99.25 99.37 99.41 99.44 99.49 99.64

250 99.32 99.42 99.46 99.49 99.54 99.67

333 99.36 99.46 99.49 99.53 99.57 99.70

DL3 500 99.42 99.51 99.54 99.57 99.61 99.73

667 99.46 99.54 99.57 99.60 99.64 99.75

833 99.49 99.57 99.60 99.62 99.66 99.76
15

Figure 2 Scaled Efficiency Curve for Single Phase Liquid-Immersed Transformers

Table 8.9 Scaled Efficiencies for Three Phase Liquid-Immersed Transformers

TSL

kVA kVA/Phase Base 1 2 3 4 5

15 5 98.36 98.51 98.61 98.67 98.77 99.29

30 10 98.62 98.74 98.83 98.88 98.97 99.40

45 15 98.76 98.86 98.95 98.99 99.07 99.46

75 25 98.91 99.00 99.07 99.11 99.18 99.52

112.5 38 99.01 99.10 99.16 99.19 99.26 99.57

DL4 150 50 99.08 99.16 99.22 99.25 99.31 99.60

225 75 99.17 99.24 99.29 99.32 99.38 99.62

300 100 99.23 99.29 99.33 99.37 99.42 99.63

500 167 99.25 99.37 99.41 99.44 99.49 99.65

750 250 99.32 99.42 99.46 99.49 99.54 99.67

1000 333 99.36 99.46 99.50 99.53 99.57 99.68

DL5 1500 500 99.42 99.51 99.54 99.57 99.61 99.69

2000 667 99.46 99.54 99.57 99.60 99.64 99.71

2500 833 99.49 99.57 99.60 99.62 99.66 99.73

Rep UnitRep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

98.50

98.70

98.90

99.10

99.30

99.50

99.70

99.90

10 100 1000

Efficiency (%)

kVA

Liquid-Immersed, 1-Phase

Base

1

2

3

4

5
16

Figure 3 Scaled Efficiency Curve for Single Phase Liquid-Immersed Transformers

8.2.2. Proposed Scaling of Efficiencies for Low-Voltage Dry-Type Transformers

Table 8.10 Scaled Efficiencies for Single Phase Low-Voltage Dry-Type Transformers

TSL

kVA Base 1

2 (NEMA 

Premium) 3 4 5 6

15 97.70 98.26 98.39 98.39 98.64 98.78 99.36

DL6 25 98.00 98.47 98.60 98.60 98.80 98.93 99.44

37.5 98.20 98.71 98.74 98.83 98.99 99.12 99.49

50 98.30 98.85 98.81 98.97 99.10 99.23 99.52

75 98.50 99.03 98.95 99.15 99.23 99.36 99.55

100 98.60 99.14 99.02 99.25 99.32 99.44 99.58

167 98.70 99.24 99.09 99.34 99.40 99.51 99.63

250 98.80 99.32 99.16 99.40 99.46 99.55 99.67

333 98.90 99.36 99.23 99.44 99.50 99.59 99.69

Rep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

98.30

98.50

98.70

98.90

99.10

99.30

99.50

99.70

99.90

100.10

10 100 1000

Efficiency (%)

kVA

Liquid-Immersed, 3-Phase

Base

1

2

3

4

5
17

Figure 4 Scaled Efficiency Curve for Single Phase Low-Voltage Dry-Type Transformers

Table 8.11 Scaled Efficiencies for Three Phase Low-Voltage Dry-Type Transformers

TSL

kVA Base 1

2 (NEMA 

Premium) 3 4 5 6

15 97.00 97.71 97.90 97.90 98.21 98.40 99.16

30 97.50 98.08 98.25 98.25 98.49 98.65 99.30

45 97.70 98.26 98.39 98.39 98.64 98.78 99.36

DL7 75 98.00 98.47 98.60 98.60 98.80 98.93 99.44

112.5 98.20 98.71 98.74 98.83 98.98 99.11 99.49

150 98.30 98.85 98.81 98.97 99.10 99.23 99.52

225 98.50 99.03 98.95 99.15 99.23 99.36 99.55

DL8 300 98.60 99.14 99.02 99.25 99.32 99.44 99.58

500 98.70 99.24 99.09 99.34 99.40 99.51 99.63

750 98.80 99.32 99.16 99.40 99.46 99.55 99.67

1000 98.90 99.36 99.23 99.44 99.50 99.59 99.69

Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.50

98.00

98.50

99.00

99.50

100.00

10 100

Efficiency (%)

kVA

Low-Voltage Dry-Type, 1-Phase

Base

1

2 (NEMA Premium)

3

4

5

6
18

Figure 5 Scaled Efficiency Curves for Three Phase Low-Voltage Dry-Type Transformers

8.2.1. Proposed Scaling of Efficiencies for Medium-Voltage Dry-Type Transformers

The efficiencies for single phase Medium-Voltage Dry-Type Transformers are scaled from the 

corresponding single phase design line. See the chapter 5. Engineering Analysis section X.X.X

Table 8.12 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 20-

45BIL

TSL

kVA Base 1 2 3 4 5

15 98.10 98.38 98.59 98.84 99.00 99.34

25 98.33 98.57 98.76 98.98 99.12 99.42

37.5 98.49 98.71 98.88 99.08 99.21 99.48

50 98.60 98.80 98.95 99.14 99.26 99.51

75 98.73 98.91 99.05 99.23 99.33 99.56

100 98.82 98.99 99.12 99.28 99.38 99.59

167 98.96 99.14 99.26 99.37 99.46 99.62

250 99.07 99.25 99.36 99.44 99.52 99.64

333 99.14 99.32 99.42 99.48 99.55 99.65

500 99.22 99.40 99.50 99.53 99.60 99.67

667 99.27 99.44 99.53 99.56 99.63 99.69

833 99.31 99.47 99.56 99.59 99.65 99.71

Rep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

96.50

97.00

97.50

98.00

98.50

99.00

99.50

100.00

10 100 1000

Efficiency (%)

kVA

Low-Voltage Dry-Type, 3-Phase

Base

1

2 (NEMA Premium)

3

4

5

6
19

Table 8.13 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 20-

45BIL

TSL

kVA Base 1 2 3 4 5

15 97.50 97.86 98.14 98.48 98.69 99.13

30 97.90 98.20 98.44 98.72 98.90 99.27

45 98.10 98.38 98.59 98.84 99.00 99.34

75 98.33 98.57 98.76 98.98 99.12 99.42

112.5 98.49 98.71 98.88 99.08 99.21 99.48

150 98.60 98.80 98.95 99.14 99.26 99.51

225 98.73 98.91 99.05 99.23 99.33 99.56

DL9 300 98.82 98.99 99.12 99.28 99.38 99.59

500 98.96 99.14 99.26 99.37 99.46 99.62

750 99.07 99.25 99.36 99.44 99.52 99.64

1000 99.14 99.32 99.42 99.48 99.55 99.65

DL10 1500 99.22 99.40 99.50 99.53 99.60 99.67

2000 99.27 99.44 99.53 99.56 99.63 99.69

2500 99.31 99.47 99.56 99.59 99.65 99.71

Figure 6 Scaled Efficiency Curves for Single Phase Medium-Voltage Dry-Type 

Transformers 20-45BIL

0

0.2

0.4

0.6

0.8

1

1.2

97.50

98.00

98.50

99.00

99.50

100.00

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 20-45 kV BIL, 

1-Phase

Base

1

2

3

4

5
20

Figure 7 Scaled Efficiency Curves for Three Phase Medium-Voltage Dry-Type 

Transformers 20-45BIL

Table 8.14 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 46-

95BIL

TSL

kVA Base 1 2 3 4 5

15 97.86 98.09 98.30 98.49 98.60 99.20

25 98.12 98.32 98.50 98.67 98.77 99.29

37.5 98.30 98.48 98.65 98.80 98.89 99.36

50 98.42 98.58 98.74 98.88 98.97 99.41

75 98.57 98.72 98.86 98.99 99.07 99.46

100 98.67 98.81 98.94 99.06 99.13 99.50

167 98.83 98.99 99.11 99.21 99.28 99.55

250 98.95 99.12 99.23 99.31 99.39 99.59

333 99.03 99.20 99.30 99.38 99.45 99.62

500 99.12 99.30 99.39 99.46 99.53 99.65

667 99.18 99.35 99.43 99.50 99.56 99.67

833 99.23 99.38 99.46 99.52 99.59 99.69

Rep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.40

97.90

98.40

98.90

99.40

99.90

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 20-45 kV BIL, 

3-Phase

Base

1

2

3

4

5
21

Table 8.15 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 46-

95BIL

TSL

kVA Base 1 2 3 4 5

15 97.19 97.48 97.76 98.01 98.16 98.94

30 97.63 97.88 98.12 98.33 98.45 99.11

45 97.86 98.09 98.30 98.49 98.60 99.20

75 98.12 98.32 98.50 98.67 98.77 99.29

112.5 98.30 98.48 98.65 98.80 98.89 99.36

150 98.42 98.58 98.74 98.88 98.97 99.41

225 98.57 98.72 98.86 98.99 99.07 99.46

DL11 300 98.67 98.81 98.94 99.06 99.13 99.50

500 98.83 98.99 99.11 99.21 99.28 99.55

750 98.95 99.12 99.23 99.31 99.39 99.59

1000 99.03 99.20 99.30 99.38 99.45 99.62

DL12 1500 99.12 99.30 99.39 99.46 99.53 99.65

2000 99.18 99.35 99.43 99.50 99.56 99.67

2500 99.23 99.38 99.46 99.52 99.59 99.69

Figure 8 Scaled Efficiency Curves Single Phase Medium-Voltage Dry-Type Transformers

46-95BIL

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.70

98.20

98.70

99.20

99.70

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 46-95 kV BIL, 1-Phase

Base

1

2

3

4

5
22

Figure 9 Scaled Efficiency Curves Three Phase Medium-Voltage Dry-Type Transformers

46-95BIL

Table 8.16 Single Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 96-

150BIL

TSL

kVA Base 1 2 3 4 5

15 97.80 98.01 98.15 98.26 98.55 99.16

25 98.06 98.25 98.37 98.47 98.73 99.26

37.5 98.25 98.42 98.53 98.62 98.85 99.34

50 98.37 98.53 98.63 98.72 98.93 99.38

75 98.53 98.67 98.76 98.84 99.03 99.44

100 98.63 98.76 98.85 98.92 99.10 99.48

167 98.80 98.94 99.03 99.09 99.23 99.51

250 98.91 99.07 99.15 99.21 99.32 99.53

333 98.99 99.14 99.22 99.28 99.37 99.55

500 99.09 99.25 99.32 99.37 99.44 99.57

667 99.15 99.31 99.38 99.43 99.49 99.58

833 99.20 99.35 99.41 99.46 99.52 99.60

Rep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.00

97.50

98.00

98.50

99.00

99.50

100.00

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 46-95 kV BIL, 3-Phase

Base

1

2

3

4

5
23

Table 8.17 Three Phase Scaled Efficiencies for Medium-Voltage Dry-Type Transformers 96-

150BIL

TSL

kVA Base 1 2 3 4 5

15 97.10 97.38 97.57 97.72 98.10 98.90

30 97.56 97.79 97.95 98.08 98.40 99.08

45 97.80 98.01 98.15 98.26 98.55 99.16

75 98.06 98.25 98.37 98.47 98.73 99.26

112.5 98.25 98.42 98.53 98.62 98.85 99.34

150 98.37 98.53 98.63 98.72 98.93 99.38

225 98.53 98.67 98.76 98.84 99.03 99.44

DL13A 300 98.63 98.76 98.85 98.92 99.10 99.48

500 98.80 98.94 99.03 99.09 99.23 99.51

750 98.91 99.07 99.15 99.21 99.32 99.53

1000 98.99 99.14 99.22 99.28 99.37 99.55

1500 99.09 99.25 99.32 99.37 99.44 99.57

DL13B 2000 99.15 99.31 99.38 99.43 99.49 99.58

2500 99.20 99.35 99.41 99.46 99.52 99.60

Figure 10 Scaled Efficiency Curves Single Phase Medium-Voltage Dry-Type Transformers

96-150BIL

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.70

98.20

98.70

99.20

99.70

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 96-150 kV 

BIL, 1-Phase

Base

1

2

3

4

5
24

Figure 11 Scaled Efficiency Curves Three Phase Medium-Voltage Dry-Type Transformers

96-150BIL

9. Chapter 11 – Life-Cycle Cost Subgroups Analysis

In analyzing the potential impacts of new or amended standards, DOE evaluates impacts on 

identifiable groups (i.e., subgroups) of customers that may be disproportionately affected by a national 

standard (see chapter 11). For this rulemaking, DOE identified rural electric cooperatives, municipal 

utilities and purchasers of vault-installed transformers (mainly utilities concentrated in urban areas) as 

subgroups that could be disproportionately affected, and examined the impact of proposed standards 

on these groups using the methodology of the LCC and PBP analysis. 

9.1. Rural Cooperatives and Municipal Utilities

The Department selected two key data inputs that it adjusted for the consumer subgroup 

analysis:

Table 8—Consumer Subgroup Economic Adjustment Factors

Subgroup Transformer Loading A and B Factors

National sample 1.00 1.00

Rural cooperatives 0.75 0.75

Municipal utilities 1.20 1.00

Rep Unit Rep Unit

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

97.00

97.50

98.00

98.50

99.00

99.50

100.00

10 100 1000

Efficiency (%)

kVA

Medium-Voltage Dry-Type, 96-150 kV 

BIL, 3-Phase

Base

1

2

3

4

5
25

For transformer loading estimates, the data available to the Department consisted of rough loading 

estimates mentioned in stakeholder comments. The Department’s estimate of average root mean 

square (RMS) loading for a 50 kVA pad-mounted transformer for the national sample is 35 percent. 

Stakeholders commented that rural cooperative transformers tend to be loaded less because of 

oversizing for voltage flicker and lack of load diversity, while municipal utility transformers tend to have 

more diversity and subsequently higher loading. The typical rural cooperative transformer will serve a 

single customer while the typical urban transformer will serve multiple customers. Thus the 

Department estimated an adjustment factor of 0.75 for rural cooperatives, and 1.20 for municipal 

utilities, which results in average RMS loading estimates of 26 percent and 42 percent for 50 kVA 

transformers for rural cooperatives and municipal utilities, respectively.

In the 2007 final rule The Department found the evaluation parameters for rural cooperatives to be 

lower than the national sample average and the parameters for municipal utilities to be slightly higher 

as the national sample average for the available data. Thus, DOE estimated and adjusted evaluation rate 

of 38 percent for rural cooperatives and 60 percent for municipal utilities.

9.2. Vault Installed Transformers

DOE calculated the volumes of those transformers selected by the LCC spreadsheets, as a function 

of CSL, for the two design lines (DLs) identified in the 2007 Final Rule for which transformer vault 

constraints are most likely to be an issue: DL4 and DL5. DOE examined the impacts of increasing 

transformer volume with regard to costs for vault enlargement. DOE assumed that if the volume of a 

transformer in a standard case is larger than the volume of the unit in the base case, a vault 

modification would be warranted. DOE also considered the instances where it would not be practical to 

modify the existing vault to overcome the space-constrained issues through vault modification and that 

a selected transformer must be of equal or lower volume then the initial baseline unit.

To estimate the cost of vault modification, DOE compared the difference in volume between the

unit selected in the base case against the unit selected in the standard case, and applied fixed and 

variable costs. In the 2007 notice of data availability, DOE estimated the fixed cost as $1,740 per 

transformer and the variable cost as $26 per transformer cubic foot, these costs were adjusted to 

2010$ using the chained price index for non-residential construction for power and communications to 

$1854 per transformer and $28 per transformer cubic foot. DOE considered instances where it may be 

extremely difficult to modify existing vaults by adding a Very High Vault Replacement Cost option to the 

LCC spreadsheet. Under this option, the fixed cost is $30,000 and the variable cost is $733 per 

transformer cubic foot.