Renewable Electricity 

Futures Study

Executive Summary

NREL is a national laboratory of the U.S. Department of Energy, 

Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Volume 2

PDF

Volume 3

PDF

Volume 1

PDF

Volume 4

PDF
Renewable Electricity Futures Study 

Edited By

Hand, M.M.

National Renewable 

Energy Laboratory

Baldwin, S.

U.S. Department of 

Energy

DeMeo, E. 

Renewable Energy 

Consulting Services, Inc.

Reilly, J.M.

Massachusetts Institute of 

Technology

Mai, T.

National Renewable 

Energy Laboratory 

Arent, D.

Joint Institute for Strategic 

Energy Analysis

Porro, G.

National Renewable 

Energy Laboratory

Meshek, M.

National Renewable 

Energy Laboratory

Sandor, D.

National Renewable 

Energy Laboratory

Suggested Citations

Renewable Electricity Futures Study (Entire Report)

National Renewable Energy Laboratory. (2012). Renewable Electricity Futures Study. Hand, M.M.; 

Baldwin, S.; DeMeo, E.; Reilly, J.M.; Mai, T.; Arent, D.; Porro, G.; Meshek, M.; Sandor, D. eds. 4 vols. 

NREL/TP-6A20-52409. Golden, CO: National Renewable Energy Laboratory. 

http://www.nrel.gov/analysis/re_futures/. 

Renewable Electricity Futures Study: Executive Summary

Mai, T.; Sandor, D.; Wiser, R.; Schneider, T (2012). Renewable Electricity Futures Study: Executive 

Summary. NREL/TP-6A20-52409-ES. Golden, CO: National Renewable Energy Laboratory.
Renewable Electricity 

Futures Study 

Executive Summary 

Trieu Mai,1 Debra Sandor,1 

Ryan Wiser,2 Thomas Schneider1 

1 National Renewable Energy Laboratory

2 Lawrence Berkeley National Laboratory
NOTICE

This report was prepared as an account of work sponsored by an agency of the United States 

government. Neither the United States government nor any agency thereof, nor any of their employees, 

makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, 

completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents 

that its use would not infringe privately owned rights. Reference herein to any specific commercial 

product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily 

constitute or imply its endorsement, recommendation, or favoring by the United States government or any 

agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect 

those of the United States government or any agency thereof.

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from:

U.S. Department of Energy

Office of Scientific and Technical Information

P.O. Box 62

Oak Ridge, TN 37831-0062

phone: 865.576.8401

fax: 865.576.5728

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from:

U.S. Department of Commerce

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

phone: 800.553.6847

fax: 703.605.6900

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/help/ordermethods.aspx

Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.
Renewable Electricity Futures Study — Executive Summary

iii 

Perspective

The Renewable Electricity Futures Study (RE Futures) provides an analysis of the grid 

integration opportunities, challenges, and implications of high levels of renewable electricity 

generation for the U.S. electric system. The study is not a market or policy assessment. Rather, 

RE Futures examines renewable energy resources and many technical issues related to the 

operability of the U.S. electricity grid, and provides initial answers to important questions about 

the integration of high penetrations of renewable electricity technologies from a national 

perspective. RE Futures results indicate that a future U.S. electricity system that is largely 

powered by renewable sources is possible and that further work is warranted to investigate this 

clean generation pathway. The central conclusion of the analysis is that renewable electricity 

generation from technologies that are commercially available today, in combination with a more

flexible electric system, is more than adequate to supply 80% of total U.S. electricity generation 

in 2050 while meeting electricity demand on an hourly basis in every region of the United States. 

The renewable technologies explored in this study are components of a diverse set of clean 

energy solutions that also includes nuclear, efficient natural gas, clean coal, and energy 

efficiency. Understanding all of these technology pathways and their potential contributions to 

the future U.S. electric power system can inform the development of integrated portfolio 

scenarios. RE Futures focuses on the extent to which U.S. electricity needs can be supplied by 

renewable energy sources, including biomass, geothermal, hydropower, solar, and wind. 

The study explores grid integration issues using models with unprecedented geographic and time 

resolution for the contiguous United States. The analysis (1) assesses a variety of scenarios with 

prescribed levels of renewable electricity generation in 2050, from 30% to 90%, with a focus on 

80% (with nearly 50% from variable wind and solar photovoltaic generation); (2) identifies the 

characteristics of a U.S. electricity system that would be needed to accommodate such levels; 

and (3) describes some of the associated challenges and implications of realizing such a future. 

In addition to the central conclusion noted above, RE Futures finds that increased electric system 

flexibility, needed to enable electricity supply-demand balance with high levels of renewable 

generation, can come from a portfolio of supply- and demand-side options, including flexible 

conventional generation, grid storage, new transmission, more responsive loads, and changes in 

power system operations. The analysis also finds that the abundance and diversity of U.S. 

renewable energy resources can support multiple combinations of renewable technologies that 

result in deep reductions in electric sector greenhouse gas emissions and water use. The study 

finds that the direct incremental cost associated with high renewable generation is comparable to 

published cost estimates of other clean energy scenarios. Of the sensitivities examined, 

improvement in the cost and performance of renewable technologies is the most impactful lever 

for reducing this incremental cost. Assumptions reflecting the extent of this improvement are 

based on incremental or evolutionary improvements to currently commercial technologies and do 

not reflect U.S. Department of Energy activities to further lower renewable technology costs so 

that they achieve parity with conventional technologies. 
Renewable Electricity Futures Study — Executive Summary

iv 

RE Futures is an initial analysis of scenarios for high levels of renewable electricity in the United 

States; additional research is needed to comprehensively investigate other facets of high 

renewable or other clean energy futures in the U.S. power system. First, this study focuses on 

renewable-specific technology pathways and does not explore the full portfolio of clean 

technologies that could contribute to future electricity supply. Second, the analysis does not 

attempt a full reliability analysis of the power system that includes addressing sub-hourly, 

transient, and distribution system requirements. Third, although RE Futures describes the system 

characteristics needed to accommodate high levels of renewable generation, it does not address 

the institutional, market, and regulatory changes that may be needed to facilitate such a 

transformation. Fourth, a full cost-benefit analysis was not conducted to comprehensively 

evaluate the relative impacts of renewable and non-renewable electricity generation options. 

Lastly, as a long-term analysis, uncertainties associated with assumptions and data, along with 

limitations of the modeling capabilities, contribute to significant uncertainty in the implications 

reported. Most of the scenario assessment was conducted in 2010 with assumptions concerning 

technology cost and performance and fossil energy prices generally based on data available in 

2009 and early 2010. Significant changes in electricity and related markets have already occurred 

since the analysis was conducted, and the implications of these changes may not have been fully 

reflected in the study assumptions and results. For example, both the rapid development of 

domestic unconventional natural gas resources that has contributed to historically low natural gas 

prices, and the significant price declines for some renewable technologies (e.g., photovoltaics) 

since 2010, were not reflected in the study assumptions. 

Nonetheless, as the most comprehensive analysis of U.S. high-penetration renewable electricity 

conducted to date, this study can inform broader discussion of the evolution of the electric 

system and electricity markets toward clean systems. 

The RE Futures team was made up of experts in the fields of renewable technologies, grid 

integration, and end-use demand. The team included leadership from a core team with members 

from the National Renewable Energy Laboratory (NREL) and the Massachusetts Institute of 

Technology (MIT), and subject matter experts from U.S. Department of Energy (DOE) national 

laboratories, including NREL, Idaho National Laboratory (INL), Lawrence Berkeley National 

Laboratory (LBNL), Oak Ridge National Laboratory (ORNL), Pacific Northwest National 

Laboratory (PNNL), and Sandia National Laboratories (SNL), as well as Black & Veatch and 

other utility, industry, university, public sector, and non-profit participants. Over the course of 

the project, an executive steering committee provided input from multiple perspectives to 

support study balance and objectivity. 

RE Futures is documented in four volumes of a single report: Volume 1—describes the analysis 

approach and models, along with the key results and insights; Volume 2 describes the renewable 

generation and storage technologies included in the study; Volume 3 presents end-use demand 

and energy efficiency assumptions; and Volume 4 discusses operational and institutional 

challenges of integrating high levels of renewable energy into the electric grid. The Executive 

Summary for RE Futures is both included in Volume 1 and presented separately here. 
Renewable Electricity Futures Study — Executive Summary

v 

Acknowledgments

The Project Leaders for the Renewable Electricity Futures Study gratefully acknowledge the 

significant contributions from the numerous individuals on the RE Futures team, more than 110 

individuals from more than 35 organizations as listed in Appendix D. We appreciate their 

thorough and thoughtful consideration of the present state and future potential of renewable 

electricity generation technologies, use of electricity, and electric sector operation. This report is 

the culmination of their contributions. We are also grateful to the members of the study’s 

executive steering committee, who assisted the RE Futures team in evolving and finalizing the 

scenarios to include and reviewed and provided comments on the analysis at various stages. We 

also thank the many outside individuals who reviewed the draft documents. 

The ability to represent the technical aspects of future electricity generation portfolios, 

particularly with high levels of renewable electricity generation, requires sophisticated models 

operated by experienced analysts. We are grateful to Walter Short for his innovation, vision and 

leadership at NREL over several decades that led to development of both the Regional Energy 

Deployment System (ReEDS) and the strong team of analysts who use this model and other tools 

to provide context and insight around future electricity generation portfolios for this study and 

many others. 

The support and guidance of management at NREL and MIT also was critical to the completion 

of this study. In particular, we recognize Robin Newmark and Bobi Garrett for their leadership. 

We are grateful to the U.S. Department of Energy (DOE) Office of Energy Efficiency and 

Renewable Energy for sponsoring this work. We especially thank Sam Baldwin for his vision 

and leadership in conceiving, supporting, and contributing to this study from beginning to end. 

We also thank DOE’s Office of Electricity Delivery and Energy Reliability for its input and 

guidance on specific aspects of the analysis, as well as valuable comments and helpful 

suggestions to improve the content of the report. NREL’s contributions to this report were 

funded by the DOE Office of Energy Efficiency and Renewable Energy under contract number 

DE-AC36-08GO28308. 
Renewable Electricity Futures Study — Executive Summary

vi 

List of Acronyms and Abbreviations

AC alternating current 

BA balancing area 

Btu British Thermal Unit(s)

CAES compressed air energy storage

CC combined cycle 

CCS carbon capture and storage

CO2 carbon dioxide 

CO2e, CO2eq carbon dioxide equivalent 

CSP concentrating solar power

CT combustion turbine 

DC direct current

DOE U.S. Department of Energy 

EEPS energy efficiency portfolio standard 

EIA U.S. Energy Information Administration

EPA U.S. Environmental Protection Agency 

EREC European Renewable Energy Council 

GHG greenhouse gases

GWEC Global Wind Energy Council 

INL Idaho National Laboratory

IPCC Intergovernmental Panel on Climate Change 

MW megawatt(s)

MWh megawatt-hour(s) 

NREL National Renewable Energy Laboratory

ORNL Oak Ridge National Laboratory 

PNNL Pacific Northwest National Laboratory

PV photovoltaic 

RE renewable electricity

RE Futures Renewable Electricity Futures Study

ReEDS Regional Energy Deployment System 

RE-ETI Renewable Electricity—Evolutionary Technology Improvement 

RE-ITI Renewable Electricity—Incremental Technology Improvement 
Renewable Electricity Futures Study — Executive Summary

vii 

RE-NTI Renewable Electricity—No Technology Improvement 

SNL Sandia National Laboratories 

SolarDS Solar Deployment System

TW terawatt(s)

TWh terawatt-hour(s) 

yr year
Renewable Electricity Futures Study — Executive Summary

viii 

Table of Contents

Perspective ................................................................................................................................................. iii

Acknowledgments ...................................................................................................................................... v

List of Acronyms and Abbreviations ....................................................................................................... vi

Study Organization and Report Structure................................................................................................ 4

Analysis Approach...................................................................................................................................... 5

Scenario Framework ..................................................................................................................5

Renewable Resources Characterization .....................................................................................9

U.S. Electricity Grid Expansion and Operational Characterization ........................................13

Key Results................................................................................................................................................ 14

Deployment of Renewable Energy Technologies in High Renewable Electricity Futures .....14

Grid Operability and Hourly Resource Adequacy in High Renewable Electricity Futures ....20

Transmission Expansion in High Renewable Electricity Futures ............................................25

Cost and Environmental Implications of High Renewable Electricity Futures .......................27

Effects of Demand Growth on High Renewable Electricity Futures .......................................29

Conclusions............................................................................................................................................... 30

Appendix. Project Participants and Contributors ................................................................................. 32

References................................................................................................................................................. 43
Renewable Electricity Futures Study — Executive Summary

ix 

List of Figures

Figure ES-1. Modeling scenario framework for RE Futures .....................................................7

Figure ES-2. Geographic distribution of renewable resources in the contiguous United 

States ..................................................................................................................................10

Figure ES-3. Installed capacity and generation in 2050 as renewable electricity levels 

increase (low-demand, RE-ITI technology improvement) ................................................15

Figure ES-4. Renewable generation and capacity in 2050 by region under 80% RE-ITI 

scenario (low-demand, RE-ITI technology improvement) ................................................17

Figure ES-5. Range of 2050 installed capacity and annual generated electricity by technology 

for the low-demand core 80% RE scenarios and the High-Demand 80% RE scenario ....19

Figure ES-6. Hourly dispatch stacks for the 80% RE-ITI scenarioa ........................................21

Figure ES-7. Operating reserve requirements as renewable electricity levels increase ..........24

Figure ES-8. New transmission capacity requirements in the baseline and exploratory 

scenarios .............................................................................................................................26

Figure ES-9. New transmission capacity additions and conceptual location in the 80% 

RE-ITI scenario ..................................................................................................................27

Figure ES-10. Average increase in retail electricity rates relative to study-specific 

reference/baseline scenarios ...............................................................................................28

 
Renewable Electricity Futures Study — Executive Summary

1 

The Renewable Electricity Futures Study (RE Futures) is an initial investigation of the extent to 

which renewable energy supply can meet the electricity demands of the contiguous United 

States1 over the next several decades. This study includes geographic and electric system 

operation resolution that is unprecedented for long-term studies of the U.S. electric sector. The 

analysis examines the implications and challenges of renewable electricity generation levels—

from 30% up to 90%, with a focus on 80%, of all U.S. electricity generation from renewable

technologies—in 2050. At such high levels of renewable electricity penetration, the unique 

characteristics of some renewable resources, specifically geographical distribution and variability

and uncertainty in output, pose challenges to the operability of the U.S. electric system. The 

study focuses on some key technical implications of this environment, exploring whether the 

U.S. power system can supply electricity to meet customer demand with high levels of renewable 

electricity, including variable wind and solar generation. The study also begins to address the 

potential economic, environmental, and social implications of deploying and integrating high 

levels of renewable electricity in the United States. 

RE Futures was framed with a few important questions:

• The United States has diverse and abundant renewable energy resources that are available 

to contribute higher levels of electricity generation over the next decades. Future 

renewable electricity generation will be driven in part by federal incentives and 

renewable portfolio standards mandated in many states.2 Practically, how much can 

renewable energy technologies, in aggregate, contribute to future U.S. electricity supply? 

• In recent years, variable renewable electricity generation capacity in the United States has 

increased considerably. Wind capacity, for example, has increased from 2.6 GW in 2000 

to 40 GW in 2010, while solar capacity has also begun to grow rapidly. Can the U.S. 

electric power system accommodate higher levels of variable generation from wind or 

solar photovoltaics (PV)? 

• Overall, renewable energy contributed about 10% of total power-sector U.S. electricity 

supply in 2010 (6.4% from hydropower, 2.4% from wind energy, 0.7% from biopower, 

0.4% from geothermal energy, and 0.05% from solar energy).3 Are there synergies that 

can be realized through combining these diverse sources, and to what extent can 

aggregating their output over larger areas help enable their integration into the power 

system? 

 

1 Alaska, Hawaii, and the U.S. Territories were not included in this study because they rely on electric grid systems 

that are not connected to the contiguous United States. However, both states and the territories have abundant 

renewable resources, and they have efforts are underway to substantially increase renewable electricity generation 

(see Volume 1, Text Box Introduction-1). 2 Some states have targets of a 20%–30% share of total electricity generation (see http://www.dsireusa.org/ for 

information on specific state standards) and are making progress toward meeting these goals. 

3 These data reflect estimates for the electric power sector only, and they exclude the end use sectors (i.e., on-site 

electric power supply that directly meets customer demands). If the end-use and electric power sectors are 

considered together, the percentage contribution from biomass would increase from 0.7% to 1.4%, and the 

contribution from solar would increase from 0.05% to 0.12%.
Renewable Electricity Futures Study — Executive Summary

2 

Multiple international studies4

 have explored the possibility of achieving high levels of 

renewable electricity penetration, primarily as a greenhouse gas (GHG) mitigation measure. RE 

Futures presents systematic analysis of a broad range of potential renewable electricity futures 

for the contiguous United States based on unprecedented consideration of geographic, temporal, 

and electric system operation aspects.

5

RE Futures explores a number of scenarios using a range of assumptions for generation 

technology improvement, electric system operational constraints, and electricity demand to 

project the mix of renewable technologies—including wind, PV, concentrating solar power 

(CSP), hydropower, geothermal, and biomass—that meet various prescribed levels of renewable

generation, from 30% to 90%. Additional sensitivity cases are focused on an 80%-by-2050 

scenario. At this 80% renewable generation level, variable generation from wind and solar 

technologies accounts for almost 50% of the total generation. 

Within the limits of the tools used and scenarios assessed, hourly simulation analysis indicates 

that estimated U.S. electricity demand in 2050 could be met with 80% of generation from 

renewable electricity technologies with varying degrees of dispatchability, together with a mix of 

flexible conventional generation and grid storage, additions of transmission, more responsive 

loads, and changes in power system operations.6 Further, these results were consistent for a wide 

range of assumed conditions that constrained transmission expansion, grid flexibility, and 

renewable resource availability. The analysis also finds that the abundance and diversity of U.S. 

renewable energy resources can support multiple combinations of renewable technologies that 

result in deep reductions in electric sector greenhouse gas emissions and water use. Further, the 

study finds that the incremental cost associated with high renewable generation is comparable to 

published cost estimates of other clean energy scenarios. Of the sensitivities examined, 

improvement in the cost and performance of renewable technologies is the most impactful level 

for reducing this incremental cost.

While this analysis suggests such a high renewable generation future is possible, a 

transformation of the electricity system would need to occur to make this future a reality. This 

transformation, involving every element of the grid, from system planning through operation, 

would need to ensure adequate planning and operating reserves, increased flexibility of the 

electric system, and expanded multi-state transmission infrastructure, and would likely rely on 

the development and adoption of technology advances, new operating procedures, evolved 

business models, and new market rules.

 

4 As examples, recent detailed studies include those prepared for Europe (ECF 2010) and Germany (SRU 2010), as 

well as a review of 164 global energy scenarios by the Intergovernmental Panel on Climate Change (IPCC 2011). 

Cochran et al. (2012) also describes several case studies of countries successfully managing high levels of variable 

renewable energy on their electric grids.

5 Previous, more conceptual or more-limited analyses of high penetrations of renewable energy in the United States 

and globally include (but are not limited to) Pacala and Socolow (2004); ACORE (2007); Kutscher (2007); 

Greenblatt (2009); GWEC/GPI (2008); Fthenakis et al. (2009); Jacobson and Delucchi (2009); Sawin and Moomaw 

(2009); EREC/GPI (2008); and Lovins (2011). 6 The study did not conduct a full reliability analysis, which would include sub-hourly, stability, and AC power 

flow analysis.
Renewable Electricity Futures Study — Executive Summary

3 

Key results of this study include the following:

• Deployment of Renewable Energy Technologies 

o Renewable energy resources, accessed with commercially available generation 

technologies, could adequately supply 80% of total U.S. electricity generation in 2050 

while balancing supply and demand at the hourly level. 

o All regions of the United States could contribute substantial renewable electricity 

supply in 2050, consistent with their local renewable resource base. 

o Multiple technology pathways exist to achieve a high renewable electricity future. 

Assumed constraints that limit power transmission infrastructure, grid flexibility, or 

the use of particular types of resources can be compensated for through the use of 

other resources, technologies, and approaches. 

o Annual renewable capacity additions that enable high renewable generation are 

consistent with current global production capacities but are significantly higher than 

recent U.S. annual capacity additions for the technologies considered. No 

insurmountable long-term constraints to renewable electricity technology 

manufacturing capacity, materials supply, or labor availability were identified. 

• Grid Operability and Hourly Resource Adequacy 

o Electricity supply and demand can be balanced in every hour of the year in each 

region with nearly 80% electricity from renewable resources, including nearly 50% 

from variable renewable generation, according to simulations of 2050 power system 

operations. 

o Additional challenges to power system planning and operation would arise in a high 

renewable electricity future, including management of low-demand periods and 

curtailment of excess electricity generation. 

o Electric sector modeling shows that a more flexible system is needed to accommodate 

increasing levels of renewable generation. System flexibility can be increased using a 

broad portfolio of supply- and demand-side options, and will likely require 

technology advances, new operating procedures, evolved business models, and new 

market rules. 

• Transmission Expansion 

o As renewable electricity generation increases, additional transmission infrastructure is 

required to deliver generation from cost-effective remote renewable resources to load 

centers, enable reserve sharing over greater distances, and smooth output profiles of 

variable resources by enabling greater geospatial diversity.

• Cost and Environmental Implications of High Renewable Electricity Futures

o High renewable electricity futures can result in deep reductions in electric sector 

greenhouse gas emissions and water use. 

o The direct incremental cost associated with high renewable generation is comparable 

to published cost estimates of other clean energy scenarios. Improvement in the cost 
Renewable Electricity Futures Study — Executive Summary

4 

and performance of renewable technologies is the most impactful lever for reducing 

this incremental cost. 

• Effects of Demand Growth

o With higher demand growth, high levels of renewable generation present increased 

resource and grid integration challenges. 

This report presents the analysis of some of the technical challenges and opportunities associated 

with high levels of renewable generation in the U.S. electric system. However, the analysis 

presented in this report represents only an initial set of inquiries on a national scale. Additional 

studies are required to more fully assess the technical, operational, reliability, economic, 

environmental, social, and institutional implications of high levels of renewable electricity 

generation, and further explore the nature of the electricity system transformation required to 

enable such a future.

Study Organization and Report Structure

RE Futures was led by a team from the National Renewable Energy Laboratory (NREL) and the 

Massachusetts Institute of Technology (MIT). The leadership team coordinated teams of subject 

matter experts from U.S. Department of Energy (DOE) national laboratories, including Idaho 

National Laboratory (INL), Lawrence Berkeley National Laboratory (LBNL), NREL, Oak Ridge 

National Laboratory (ORNL), Pacific Northwest National Laboratory (PNNL), and Sandia 

National Laboratories (SNL), as well as Black & Veatch and other utility, industry, university, 

public sector, and non-profit participants. These expert teams explored the prospects for largescale deployment of specific renewable generation and storage technologies, along with some of 

the issues and challenges associated with their integration into the electric system. 

In total, this report is the culmination of contributions from more than 110 individuals at more 

than 35 organizations (Appendix D lists the contributors to the study). Over the course of the 

project, an executive steering committee provided input from multiple perspectives to support 

study balance and objectivity. Technical reviewers from the renewable technology and electric 

sector industries, universities, public sector, non-profits, and other entities commented on a 

preliminary version of this report.

Most of the analysis informing the study, particularly the scenario assessment, was conducted in 

2010. As a result, study assumptions concerning technology cost and performance and fossil 

energy prices were generally based on data available in late 2009 and early 2010. Where 

possible, more recent published work has been referenced; however, the implications of these 

publications may not have been fully reflected in the RE Futures study assumptions. For 

example, both the rapid development of domestic unconventional natural gas resources that has 

contributed to historically low natural gas prices, and the significant price declines for some 

renewable technologies (e.g., photovoltaics) since 2010, were not reflected in the study 

assumptions. Finally, the technology projections presented in RE Futures do not necessarily 

reflect the current DOE estimates. 

RE Futures is documented in four volumes of a single report: Volume 1—describes the analysis 

approach and models, along with the key results and insights. Volume 2 describes the renewable 

generation and storage technologies included in the study; Volume 3 presents 2050 end-use 
Renewable Electricity Futures Study — Executive Summary

5 

demand and energy efficiency assumptions; and Volume 4 discusses some operational and 

institutional challenges of integrating high levels of renewable energy into the electric grid. 

This Executive Summary, which is also included in Volume 1, highlights the analysis approach 

and key results from RE Futures. First, it summarizes the analysis approach, including scenario 

framework, renewable resources characterization, and modeling tools used to analyze the 

expansion of the U.S. electricity system and its operational characteristics. The key results from 

the analysis are then presented, including results associated with renewable technology 

deployment, grid operations, and economic, environmental and social implications. Finally, 

additional research opportunities are identified in the conclusions. 

Analysis Approach

Scenario Framework

Given the inherent uncertainties involved with analyzing alternative long-term energy futures, 

and given the variety of pathways that might lead to higher levels of renewable electricity 

supply, multiple future scenarios were modeled and analyzed. The scenarios examined included 

the following considerations: 

• Energy Efficiency: Most of the scenarios assumed adoption of energy efficiency 

(including electricity) measures in the residential, commercial, and industrial sectors that 

resulted in flat demand growth over the 40-year study period.7

• Transportation: Most of the scenarios assumed a shift of some transportation energy 

away from petroleum and toward electricity in the form of electric and plug-in hybrid 

electric vehicles, partially offsetting the electricity efficiency advances that were 

considered.

8

 

• Grid Flexibility: Most scenarios assumed improvements in electric system operations to 

enhance flexibility in both electricity generation and end-use demand, helping to enable 

more efficient integration of variable-output renewable electricity generation. 

• Transmission: Most scenarios expand the transmission infrastructure and access to 

existing transmission capacity to support renewable energy deployment. Distributionlevel upgrades were not considered. 

• Siting and Permitting: Most scenarios assumed project siting and permitting regimes 

that allow renewable electricity development and transmission expansion subject to

standard land-use exclusions. 

 

7 The efficiency gains assumed are described in Volume 3. They do not represent an upper bound of energy 

efficiency, i.e., they were not as large as estimated by NAS/NAE (2010). 8 The flat demand (low-demand) projection included this increase in demand from the transportation sector, whereas 

the business-as-usual demand (high-demand) projection did not. The contribution of biofuels to the transportation 

sector is not quantified in RE Futures.
Renewable Electricity Futures Study — Executive Summary

6 

In all the scenarios analyzed, only currently commercially available technologies (as of 2010) 

were considered, together with their incremental or evolutionary improvements despite the longterm (2050) timeframe, because the focus of this study was on grid integration and not on the 

potential advances of any individual technologies.9 Technologies such as enhanced geothermal 

systems; ocean energy technologies (e.g., wave, tidal, current or ocean thermal); floating 

offshore wind technology; and others that are currently under development and pilot testing—

and which show significant promise but are not yet generally commercially available—were not 

included. 

More than two dozen scenarios were modeled and analyzed in this study as outlined in Figure 

ES-1 and detailed below. The number and diversity of scenarios allowed an assessment of 

multiple pathways that depended on highly uncertain future technological, institutional, and 

market choices. The framework included scenarios with specific renewable electricity generation 

levels to enable exploration of some of the technical issues associated with the operation of the 

U.S. electricity grid at these levels.10 This scenario framework does not prescribe a set of policy 

recommendations for renewable electricity generation in the United States, nor does it present a 

vision of what the total mix of energy sources should look like in the future. Further, the 

framework does not intend to imply that one future is more likely than another. 

 

9 RE Futures did not allow new nuclear plants, fossil technologies with CCS, as well as gasified coal without CCS 

(integrated gasification combined cycle) to be built in any of the scenarios presented in this report. Existing nuclear 

(and integrated gasification combined cycle) units, however, were included in the analysis, as were assumptions for 

the retirement of those units. 10 The scenarios were not constructed to find the optimal GHG mitigation or clean energy pathway (e.g., to 

minimize carbons emissions or the cost of mitigating these emissions). In addition, because the scenarios included 

specific renewable generation levels, they were not designed to explore how renewable technologies might 

economically deploy under certain technology advancement projections without the generation constraints.
Renewable Electricity Futures Study — Executive Summary

7 

Figure ES-1. Modeling scenario framework for RE Futures 

Dotted lines indicate that the 80% RE exploratory scenarios are the same as the 80% 

RE-ITI and 80% RE-ETI scenarios. 

Low-Demand Baseline Scenario 

A Low-Demand Baseline scenario was designed to reflect a largely conventional generation 

system as a point of comparison, or reference, for the high-penetration renewable electricity 

scenarios. The Low-Demand Baseline scenario assumes that a combination of emerging trends—

including policies and legislation dealing with codes and standards, innovation in energy 

efficiency, and the green building and supply chain movements—drive the adoption of energy 

efficiency measures in the residential, commercial, and industrial sectors (see Volume 3 for 

details).

11 Substantial adoption of electric and plug-in hybrid electric vehicles was also assumed. 

In aggregate, these low-demand assumptions resulted in overall electricity consumption that 

exhibits little growth from 2010 to 2050. Existing state policies (e.g., renewable portfolio 

standards) and existing federal policies (e.g., investment tax credits, production tax credits, tax 

depreciation rules) were assumed to continue only as allowed under existing law, with no 

 

11 In addition to these trends, the primary historical drivers of electricity demand, population growth, and economic 

growth, were also considered in the construction of the scenario. While investment costs of these efficiency 

measures were not considered in the scenario development, findings from other studies generally indicate that such 

measures can be considered cost-effective or cost-competitive. 
Renewable Electricity Futures Study — Executive Summary

8 

extensions. Expiration dates for existing federal policies vary, but generally are 2017 or earlier.12

In combination with incremental technology improvements, these assumptions result in low 

levels of renewable electricity generation in the Low-Demand Baseline scenario.

Exploratory Scenarios

A series of “exploratory scenarios,” in which the proportion of renewable electricity in 2050 

increased in 10% increments from 30% to 90%, was evaluated. The primary purpose of these 

exploratory scenarios was to assess how increased levels of renewable electricity might impact 

the generation mix of renewable and non-renewable resources, the extent of transmission 

expansion in these cases, and the use of various forms of supply- and demand-side flexibility to 

enable a match between electricity supply and demand. These exploratory scenarios were 

evaluated under two distinct sets of renewable electricity technology advancement assumptions: 

Incremental Technology Improvement (ITI) and Evolutionary Technology Improvement (ETI).

Core 80% RE Scenarios

Further analysis was performed on six core 80% RE scenarios, each of which met the same 80%-

by-2050 renewable electricity penetration level and each of which was designed to elucidate the 

possible implications of certain technological, institutional, and market drivers.13 Three scenarios 

explored the impacts of future renewable energy technology advancements of currently 

commercial technologies and the resulting deployment of different combinations of renewable 

energy technologies14: 

• The RE – No Technology Improvement (80% RE-NTI) scenario simply assumed that the 

performance of each renewable technology was maintained at 2010 levels for all years in 

the study period (2010–2050). 

• The RE – Incremental Technology Improvement (80% RE-ITI) scenario reflected only 

partial achievement of the future technical advancements that may be possible (Black & 

Veatch 2012). 

• The RE – Evolutionary Technology Improvement (80% RE-ETI) scenario reflected a 

more-complete achievement of possible future technical advancements (Volume 2). The 

RE-ETI scenario is not designed to be a lower bound and does not span the full range of 

possible futures; further technical advancements beyond the RE-ETI are possible.15 

Three additional scenarios explored the impacts of different electricity system constraints based 

on assumptions that limited the building of new transmission, reduced system flexibility to

 

12 Similarly, indirect incentives for conventional energy technologies—sometimes delivered through the tax code 

without sunset provisions —were assumed to be maintained as allowed under existing law. These same renewable 

and conventional technology policy assumptions were consistently applied to all the other scenarios as well. 13 The specific assumptions used for these scenarios are discussed in Chapter 1. 14 Although the methods used in RE Futures to project the future cost of each renewable electricity technology differ 

to some degree by technology, the resulting forecasts are largely based on anticipated scientific and engineering 

advancements rather than on learning-curve-based estimates that are endogenously driven by an assumed learning 

rate applied to cumulative production or installation. In reality, costs may decline in part due to traditional learning 

and in part due to other factors, such as research and development investment, economies of scale in manufacturing, 

component, or plant size, and reductions in material costs. 15 Indeed, current DOE initiatives are focused on achieving substantially better cost and performance in many cases,

with a target of achieving parity with conventional technologies.
Renewable Electricity Futures Study — Executive Summary

9 

manage the variability of wind and solar resources, and decreased renewable resource 

availability: 

• The Constrained Transmission scenario evaluated how limits to building new 

transmission might impact the location and mix of renewable resources used to meet an 

80%-by-2050 future. 

• The Constrained Flexibility scenario sought to understand how institutional constraints to 

and concerns about managing the variability of wind and solar resources, in particular, 

might impact the resource mix of achieving an 80%-by-2050 future. 

• The Constrained Resources scenario posited that environmental or other concerns may 

reduce the developable potential for many of the renewable technologies in question, and 

evaluated how such constraints could impact the resource mix of renewable energy 

supply. 

High-Demand Scenarios 

The scenarios described above—the Low-Demand Baseline scenario, the exploratory scenarios, 

and the six core 80% RE scenarios—were based on the low-demand assumptions, with overall 

electricity consumption that exhibits little growth from 2010 to 2050. To test the impacts of a 

higher-demand future, a scenario with the 80%-by-2050 renewable electricity generation but a 

higher end-use electricity demand was evaluated, with demand in 2050 30% higher than in the 

low-demand scenarios.

16 A corresponding reference scenario, the High-Demand Baseline 

scenario, with the same higher demand was also evaluated.

17 

Alternative Fossil Scenarios 

Finally, given uncertainties in the future cost of fossil energy sources, the analysis included 80%-

by-2050 RE scenarios in which: (1) the price of fossil energy (coal and natural gas) was both 

higher and lower than otherwise assumed in the other scenarios and (2) fossil energy 

technologies18 experienced greater technology improvements over time than assumed in the 

other scenarios. Corresponding reference scenarios with these alternate fossil energy projections 

were also evaluated. 

Renewable Resources Characterization

The United States has diverse and abundant renewable resources, including biomass, geothermal, 

hydropower, ocean, solar, and wind resources. Solar and wind are the most abundant of these 

resources. These renewable resources are geographically constrained but widespread—most are 

distributed across all or most of the contiguous states (Figure ES-2). Within these broad resource 

types, a variety of commercially available renewable electricity generation technologies have 

been deployed in the United States and other countries, including stand-alone biopower, co-fired 

 

16 The low-demand scenarios assume an annual growth rate of 0.17%; the high-demand scenarios assume an annual 

growth rate of 0.84%. Details on end-use energy demand assumptions are provided in Volume 3 of this report. 17 For comparison, all high renewable electricity scenarios require a baseline or reference scenario that uses the same 

high-level assumptions regarding electricity demand. 18 Consistent with the study’s focus on commercially available renewable generation technologies, emerging fossil 

and nuclear technologies, such as carbon-capture and sequestration and modular nuclear plants, were not included.
Renewable Electricity Futures Study — Executive Summary

10 

biopower (in coal plants), hydrothermal geothermal, hydropower, distributed PV, utility-scale 

PV, CSP,19 onshore wind, and fixed-bottom offshore wind. 

Figure ES-2. Geographic distribution of renewable resources in the contiguous

United States

The United States has potential ocean energy and enhanced geothermal resources; however, these 

technologies were not modeled and therefore the resource potential is not included in this figure. 

While only commercially available biomass, geothermal, hydropower, solar PV, CSP, and windpowered systems were considered in the modeling analysis—only incremental and evolutionary 

advances in renewable technologies were assumed—the study describes a broad range of 

commercial and emerging renewable energy technologies in Volume 2, including the 

following20: 

 

19 In this report, CSP refers to concentrating solar thermal power. Concentrating photovoltaic technologies were not 

considered in the modeling analysis. 

20 The renewable resource characterizations described below and used in the models are based on historical climatic 

average resource patterns and have standard land area exclusions applied. After accounting for these standard 

exclusions, the aggregate renewable generation resource is many times greater than current electricity demand. 
Renewable Electricity Futures Study — Executive Summary

11 

• Biomass power (Chapter 6, Volume 2) is generated by collecting and combusting plant 

matter and using the heat to drive a steam turbine. Biomass resources from agricultural 

and forest residues, although concentrated primarily in the Midwest and Southeast, are 

available throughout the United States. While biomass supply is currently limited, 

increased supply is possible in the future from increased production from energy crops 

and advanced harvesting technologies. DOE (2011) provides an estimate of 696–1,184 

million annual dry tonnes of biomass inventory potential (of which 52%–61% represents 

dedicated biomass crops) in 2030.21 The estimated biomass feedstocks correspond to 

roughly 100 GW of dedicated biopower capacity. Biopower can be generated from standalone plants, or biomass can be co-fired in traditional pulverized coal plants. 

• Geothermal power (Chapter 7, Volume 2) is generated by water that is heated by hot 

underground rocks to drive a steam turbine. Geothermal resources are generally 

concentrated in the western United States, and they are relatively limited for 

hydrothermal technologies (36 GW of new technical resource potential), which rely on 

natural hot water or steam reservoirs with appropriate flow characteristics. Only 

commercially available hydrothermal technologies were included in the modeling 

analysis. Although not modeled, emerging technologies, including enhanced geothermal 

systems, engineered hydrothermal reservoirs, geopressured resources, low temperature 

resources, or co-production from oil and gas wells, could expand the geothermal resource 

potential in the United States by more than 500 GW. 

• Hydropower (Chapter 8, Volume 2) is generated by using water—from a reservoir or 

run-of-river—to drive a hydropower turbine. Run-of-river technology could produce 

electricity without creating large inundated areas, and many existing dams could be 

equipped to generate electricity. The future technical potential of run-of-river 

hydropower from within the contiguous United States is estimated at 152–228 GW. Only 

new run-of-river hydropower capacity was considered in RE Futures modeling, and 

existing hydropower plants were assumed to continue operation. Other hydropower 

technologies, such as new generation at non-powered dams and constructed waterways, 

have the potential to contribute to future electricity supply, but they were not modeled in 

this study. 

• Ocean technologies (Chapter 9, Volume 2) are not broadly commercially available at 

this time, and therefore were not modeled in this study, but both U.S. and international 

research and development programs are working to reduce the cost of the technologies. 

Ocean current resources are best on the U.S. Gulf and South Atlantic Coasts; wave 

energy resources are strongest on the West Coast. All resources are uncertain; 

preliminary estimates indicate that the U.S. wave energy technical potential is on the 

order of 2,500 TWh/yr. Other ocean technologies, including ocean thermal energy 

conversion technologies and tidal technologies, may also contribute to future electricity 

supply. 

 

21 To be conservative, for each modeled year, the analysis used feedstock estimates from Walsh et al. (2000) and 

Milbrandt et al. (2005), which are consistent with the low end of the DOE (2011) estimate for 2030, and did not 

assume any increase in resource over time; on the other hand, the analysis also did not include potential future 

growth in demand for biomass from the fuel sector. Maximum biopower capacity deployment was assumed to be 

roughly 100 GW in this study, with 27% from dedicated biomass crops.
Renewable Electricity Futures Study — Executive Summary

12 

• Solar resources (Chapter 10, Volume 2) are the most abundant renewable resources. 

They extend across the entire United States, with the highest quality resources 

concentrated in the Southwest. The technical potential of utility-scale PV and CSP 

technologies is estimated to be approximately 80,000 GW and 37,000 GW, respectively, 

in the United States. Distributed rooftop PV technologies are more limited, with 

approximately 700 GW available. PV technologies convert sunlight directly to electricity

while CSP technologies collect high temperature heat to drive a steam turbine. 

• Wind resources (Chapter 11, Volume 2) on land are abundant, extending throughout the 

United States, and offshore resources provide additional options for coastal and Great 

Lakes regions. Onshore and fixed-bottom offshore technologies are currently 

commercially available.22 Floating platform offshore wind technologies that could access 

high-quality wind resources in deeper waters are less mature and were not considered in 

the modeling. Wind technical resource estimates exceed 10,000 GW in the contiguous 

United States. 

Renewable resource supply varies by location and, in most cases, by the time of day and season. 

The electricity output characteristics of some renewable energy technologies also vary 

substantially, potentially introducing electric system operation challenges. A key performance 

characteristic of generators in general is their degree of dispatchability, specifically the ability of 

operators to control power plant output over a range of specified output generation levels. 

Conventional fossil plants are considered dispatchable, to varying degrees. Several renewable 

generator types, including biopower, geothermal, and hydropower plants with reservoir storage, 

are also considered dispatchable technologies in that system operators have some ability to 

specify generator output, if needed. Concentrating solar power with thermal storage can similarly 

be considered a dispatchable technology but is limited by the amount of storage. The output from 

run-of-river hydropower is generally constant over short time periods (minutes to hours) but 

varies over longer periods (days to seasons). Several emerging ocean technologies, such as 

ocean-current, may also provide fairly constant output and, in some cases, may be able to offer 

some level of dispatchability. 

Wind and solar PV have little dispatchability—the output from these sources can be reduced, but 

not increased on demand. An additional challenge is the variability and uncertainty in the output 

profile of these resources, with wind and solar having limited predictability over various time 

scales. High levels of deployment of these generation types can therefore introduce new 

challenges to the task of ensuring reliable grid operation. However, it deserves note that the 

requirement for balanced supply and demand must be met on an aggregate basis—the variability 

and uncertainty of any individual plant or load entity does not ultimately define the integration 

challenge associated with high levels of variable renewable generation. 

The analysis presented here focuses on electricity generation technology deployment, system 

operational challenges, and implications associated with specified levels of renewable 

generation, which represent the total annual renewable electricity generation from commercially

available biomass, geothermal, hydropower, solar, and wind electricity generating technologies. 

 

22 Although there are no offshore wind power plants operating in the United States, a number of projects have been 

proposed. In addition, offshore wind is widely deployed in Europe.
Renewable Electricity Futures Study — Executive Summary

13 

U.S. Electricity Grid Expansion and Operational Characterization

RE Futures employs two key models to characterize U.S. electricity grid operations with high 

levels of renewable generation. The NREL Regional Energy Deployment System (ReEDS) 

model explores the adequacy of the geographically diverse U.S. renewable resources to meet

electricity demand over future decades. The ABB model, GridView, explores the hourly 

operation of the U.S. grid with high levels of variable PV and wind generation.23 The linked-butseparate use of the two models, ReEDS and GridView, allows for a rich assessment of the 

technical, geographic, and operational aspects of renewable energy deployment.24 

ReEDS is the analytical backbone of the study, providing estimates of the type and location of 

conventional and renewable resource development; the transmission infrastructure expansion 

requirements of those installations; and the composition and location of generation, storage, and 

demand-side technologies needed to maintain balance between supply and demand. ReEDS is 

unique among national, long-term capacity expansion models for its highly discretized regional 

structure and statistical treatment of the impact of variable wind and solar resources on capacity 

planning and dispatch. GridView was used to supplement the ReEDS analysis by modeling the 

hourly operation of the power system in 2050 for a subset of the high renewable scenarios. As 

one of the commercially available production cost models used by utilities, systems operators, 

and industry experts, GridView enables a more detailed exploration of the operational 

implications of a system with high levels of renewable electricity penetration through the use of 

an hourly time step, a more accurate representation of thermal generation ramp-rate limits, and a 

more realistic representation of transmission power flows compared with ReEDS.

These models were used to investigate a broad portfolio of supply- and demand-side options 

available to increase the flexibility of the electric system, including: having dispatchable 

renewable or conventional generators available to supply needed electricity when there is 

insufficient electricity generation from variable renewable plants; having the ability to provide 

reserves or change electricity demand through demand response (interruptible load) or 

transportation electric loads; deploying storage technologies for added system flexibility; and 

expanding the electric system transmission infrastructure to move more distant electricity supply 

to meet the load. Geospatial diversity was also taken into account, since it can assist in the 

integration of variable renewable generation because wind and solar plants that are located far

apart generally have a combined output profile that is less variable than the individual plant 

profiles. Further, wind and solar resources may be uncorrelated or even anti-correlated 

depending on location; if so, combining their outputs would then further reduce aggregate 

variability.

 

23 The NREL Solar Deployment Systems (SolarDS) model was also used in RE Futures to represent rooftop PV 

deployment.

24 In assessing high penetrations of variable renewable electricity, RE Futures addressed some aspects of electric 

system adequacy through statistical treatments of reserve requirements and hourly dispatch analysis; however, the 

analysis did not include a complete assessment of power system reliability (addressing such issues as stability, 

contingencies, and AC power flows). Similarly, RE Futures is not a fully detailed renewable energy integration 

study. Such studies typically seek to understand the impacts of variable and uncertain wind and solar generation on 

the operations of regional electric power systems and networks, relying on high time-resolution data and using 

methods that range from statistical analysis and production cost modeling to power flow simulations and steady state 

and transient grid analysis. RE Futures assessed electric system integration issues on a broader, national level, and 

the modeling tools used considered the variability and uncertainty of some renewable technologies, but not to the 

level of detail typical in integration studies.
Renewable Electricity Futures Study — Executive Summary

14 

Key Results

Deployment of Renewable Energy Technologies in High Renewable Electricity 

Futures

Renewable energy resources, accessed with commercially available renewable generation 

technologies, could adequately supply 80% of total U.S. electricity generation in 2050 while 

balancing supply and demand at the hourly level. Figure ES-3 presents estimated 2050 capacity 

and generation, by technology, for the exploratory scenarios.25 Generation from wind and PV 

technologies is variable, with lower capacity factors and relatively limited dispatchability. The 

growing deployment of this variable generation in these scenarios, increasing with renewable 

electricity penetration (from 20% in the baseline scenario to as high as 90% at the other end), 

drives the need for a growing amount of aggregate electric generation capacity in order to meet 

demand. Specifically, adequate capacity from dispatchable resources is required to ensure 

delivery of necessary generation year-round. 

Commercially available renewable technologies were deployed in the modeling to varying 

degrees in the exploratory scenarios, in part to exploit geographic and temporal diversity in 

achieving high renewable electricity penetration levels. Onshore wind was found to contribute 

most significantly in these exploratory scenarios, with offshore wind becoming an increasingly 

important player as higher renewable electricity levels were achieved. Among the solar 

technologies, PV (utility-scale and rooftop, combined) was generally found to play a moresizable role than CSP under the relatively lower renewable penetration scenarios. Electricity 

supply from CSP was projected to grow more rapidly under the higher renewable penetration

scenarios, in part because CSP with thermal storage provides added dispatchability. Both 

dedicated and co-fired biomass were also found to contribute significantly to the renewable 

energy mix, with a shift from co-firing to dedicated biomass plants as renewable electricity 

penetration levels increased. Geothermal and hydropower were found to contribute 

proportionately less than the other renewable energy sources, especially under the highest 

renewable electricity scenarios considered, due to assumed resource and cost constraints.26

However, even for this limited set of geothermal and hydropower resources, capacity expansion 

was substantial relative to recent trends, and much of the estimated available resource potential 

was accessed. Enhanced geothermal systems, ocean energy, and floating platform offshore wind 

energy were not considered, but these technologies may offer large resource potential, additional 

diversity, and regional advantages if technological advancements enable commercialization. 

 

25 Deployment results shown in Figure ES-3 used the renewable electricity incremental technology improvement 

(RE-ITI) assumptions. Results for the RE-ETI scenarios are included in Chapter 2. 26 The assumptions used in the analysis were particularly constraining on geothermal technologies, for which 

advanced technologies, such as enhanced geothermal systems that can tap large quantities of energy inside the earth, 

were not considered in the grid modeling. The modeling analysis focused on currently commercial technologies 

only.
Renewable Electricity Futures Study — Executive Summary

15 

(a) Capacity mix in 2050 for the exploratory scenarios

(b) Generation mix in 2050 for the exploratory scenarios

Figure ES-3. Installed capacity and generation in 2050 as renewable electricity levels increase

(low-demand, RE-ITI technology improvement)
Renewable Electricity Futures Study — Executive Summary

16 

All regions of the United States could contribute substantial renewable electricity supply in 

2050, consistent with their local renewable resource base. Figure ES-4 presents the modeled 

location of renewable electricity generation and capacity by 2050 for one 80%-by-2050 RE 

scenario (80% RE-ITI). It also compares total regional electricity generated in 2050 to regional 

electricity demand (based on low-demand assumptions). In the scenario shown, wind energy 

supply was significant in most regions but was most prominent in the Great Plains, Great Lakes, 

Central, Northeast, and Mid Atlantic regions (with a large fraction of wind generation coming 

from offshore resources in the Northeast and Mid Atlantic regions). Solar energy was found to 

deploy most substantially in the Southwest (dominated by CSP), followed by California and 

Texas (CSP and PV), and then by the Florida and the Southeast regions (dominated by PV). 

Biomass supply was most significant in the Great Plains, Great Lakes, Central, and Southeast 

regions. Hydropower supply was most significant in the Northwest, but hydropower was also a 

sizable contributor in California, the Northeast, and the Southeast. Geothermal was found to 

deploy primarily in California and the Southwest.
Renewable Electricity Futures Study — Executive Summary

17 

Figure ES-4. Renewable generation and capacity in 2050 by region under 80% RE-ITI scenario (low-demand, RE-ITI

technology improvement) 
Renewable Electricity Futures Study — Executive Summary

18 

Multiple technology pathways exist to achieve a high renewable electricity future. Assumed 

constraints, which limit power transmission infrastructure, grid flexibility, or the use of 

particular types of resources can be compensated for through the use of other resources, 

technologies, and approaches. The renewable energy resource base of the United States is both 

abundant and diverse. As a result, a central finding of the analysis is that there are many possible 

ways to achieve high renewable penetration levels. 

For example, the technology improvement scenarios included in the six core 80% RE scenarios 

(Impact of Technology Improvement scenarios) showed that technologies that are currently at 

earlier stages of commercialization (e.g., solar) could achieve greater deployment if significant 

technology improvements were realized in the future. In contrast, if these improvements were 

not realized, currently more commercially mature technologies (e.g., onshore wind) could deploy 

to a greater extent. Also, a set of scenarios included in the core 80% RE scenarios explored the 

impacts of limits on building new transmission, constraints on the flexibility of the electric 

system to manage the variability of wind and solar resources, and constraints on the developable 

potential for many renewable technologies (Impact of System Constraints scenarios). The mix of 

renewable resources deployed and the deployment of flexible supply- and demand-side 

technologies were significantly impacted in these scenarios. In particular, when new 

transmission builds were constrained, greater deployment was observed for resources located 

closer to load centers, including PV, offshore wind, and biomass. A future where the flexibility 

of the electric system was limited resulted in a shift of renewable electricity supply away from 

variable wind and PV technologies and toward more dispatchable options, particularly CSP with 

thermal storage, and to storage technologies. When the assumed availability of renewable energy 

supply was reduced—due to siting or permitting challenges, for example—the contributions 

from the most resource-constrained technologies (biopower, geothermal, and hydropower) 

declined, while more abundant wind and solar resources were used to a greater degree. Figure 

ES-5 shows the range in 2050 capacity and generation by technology among the six low-demand 

80%-by-2050 RE scenarios examined. Although the type and quantity of renewable technologies 

deployed in these scenarios varied significantly, estimated direct electric sector aggregate cost 

was relatively insensitive to most of these variations.

27 

Finally, the analysis found that the renewable resource base in the United States was sufficient to 

support 80% renewable electricity generation by 2050 in a higher demand growth scenario. 

Figure ES-5 also shows 2050 deployment results for the High-Demand 80%-by-2050 RE 

scenario, which features a much greater amount of solar capacity compared with the low-demand 

scenarios. 

 

27 See individual technology chapters in Volume 2 for a discussion of the specific scenarios that lead to high and low 

estimates for each technology individually; Volume 1 provides more discussion of the operational and cost 

implications these scenarios. 
Renewable Electricity Futures Study — Executive Summary

19 

(a) 2050 installed capacity by technology (b) 2050 contribution to total generated 

electricity

Figure ES-5. Range of 2050 installed capacity and annual generated electricity by technology for 

the low-demand core 80% RE scenarios and the High-Demand 80% RE scenario

Annual renewable capacity additions that enable high renewable electricity are consistent with 

current global production capacities but are significantly higher than recent U.S. annual 

capacity additions for the technologies considered. No insurmountable long-term constraints to 

renewable electricity technology manufacturing capacity, materials supply, or labor availability 

were identified. The analysis showed that achieving high renewable electricity futures would 

require a sustained increase in renewable capacity additions. In the core 80% RE scenarios, 

average annual renewable capacity additions of 19–22 GW/yr from 2011–2020 were estimated, 

increasing to a maximum rate of 32–46 GW/yr from 2041–2050. Given recent historical 

experience with U.S. renewable electricity capacity additions (11 GW in 2009 and 7 GW in 

2010),28 achieving these rates of deployment may pose challenges as production ramps up, 

including those related to materials availability, equipment manufacturing capacity, labor needs, 

and project development and siting processes. However, no insurmountable long-term technical 

constraints to renewable technology manufacturing capacity, materials supply, or labor 

availability were identified; better informed siting practices and regulations can mitigate 

potential constraints related to project development and siting processes (see Chapter 3 and 

Volume 2). 

Growth in renewable capacity additions in the United States and globally over the last decade 

has been considerable, and it demonstrates the ability to scale manufacturing and deployment at 

a rapid pace. The wind power additions required in the scenarios, for example, were substantial, 

 

28 The challenges associated with the rates of deployment presented here depend on technology. For example, 

renewable installations in the United States in recent years were dominated by new wind technologies; therefore, 

achieving the deployment rates envisioned in the scenarios for wind energy would likely be less challenging from an 

industry growth perspective compared with other technologies.
Renewable Electricity Futures Study — Executive Summary

20 

but historical growth in manufacturing and installation suggests that manufacturing need not be a 

major constraint to the continued growth that would be necessary to meet an 80%-by-2050 

generation level. The biopower and geothermal additions resulting from the scenario modeling, 

although greater than recent historical trends, are similarly unlikely to place undue strain on 

supply chains. The estimated rate of PV deployment is particularly high, but PV manufacturing 

and deployment are highly scalable, and worldwide PV production capacity has been growing 

rapidly and is already comparable to the deployment rates projected in high renewable scenarios

presented here for the United States. Moreover, many of the renewable technologies are based on 

common materials that are not supply-constrained. Even for PV, which does use some materials 

that may be supply-constrained, worldwide production capacity is already sizable and that 

capacity continues to expand rapidly. In addition, alternate approaches exist to reduce 

dependence on supply-constrained materials if necessary. While a comprehensive analysis of 

industry scale-up, including labor demands and access to critical materials, is beyond the study 

scope, the initial analysis did not identify any insurmountable technical challenges associated 

with industry scale-up at the technology deployment levels considered. 

Grid Operability and Hourly Resource Adequacy in High Renewable Electricity 

Futures

Electricity supply and demand can be balanced in every hour of the year in each region with 

nearly 80% of electricity from renewable resources, including nearly 50% from variable 

renewable generation, according to simulations of 2050 power system operations.

29 Although a 

full reliability assessment is beyond the scope of this analysis, hourly production simulation did 

consider unit commitment with imperfect forecasts, DC optimal power flow, and thermal 

generator flexibility limits (e.g., ramp rates and minimum generation levels). Figure ES-6 shows 

nationwide dispatch by generator type during the annual peak coincident load (Figure ES-6[a]) 

and during the lowest coincident load of the year (Figure ES-6[b]) in 2050 for a high renewable 

electricity scenario. The operational simulations did not project any hours of unserved load 

during the peak load hour, lowest coincident load hour, or any other hour of the year.30

 

29 Although the capacity expansion modeling (ReEDS) planned for renewable resources to contribute 80% of annual 

generation in 2050, the hourly operational model (GridView) simulated roughly 75%, in part due to a lack of a 

renewable generation requirement. GridView model dispatch decisions were based on the variable cost of generation 

and did not consider the renewable or non-renewable nature of the generation source. 30 The electric system is a complex system of systems that operates on many time scales ranging from milliseconds 

to years; ultimately, analyses must be conducted to address all of the potential operating aspects of future electricity 

generation systems as they evolve. Electric system operations are described in detail in Volume 4.
Renewable Electricity Futures Study — Executive Summary

21 

 (a) Summer peak load in 2050

 (b) Lowest coincident load in 2050

Figure ES-6. Hourly dispatch stacks for the 80% RE-ITI scenarioa

a The solid black line representing “load” includes charging of electric vehicles. The 

broken line representing “shifted load” represents “load” minus storage. The Gas CT 

category includes a small number of oil-fired units. The unit types are ordered 

(subjectively) from least variable or flexible (at the bottom) to most variable (at the top).

0

100

200

300

400

500

600

700

800

Jul-16

00:00

Jul-16

12:00

Jul-17

00:00

Jul-17

12:00

Jul-18

00:00

Jul-18

12:00

Jul-19

00:00

Jul-19

12:00

Power (GW)

Date

Curtailment

Wind

PV

Gas CT

Gas CC

Hydropower

CSP

Biopower

Coal

Geothermal

Nuclear

Shifted Load

Load

0

100

200

300

400

500

600

700

800

Apr-27

00:00

Apr-27

12:00

Apr-28

00:00

Apr-28

12:00

Apr-29

00:00

Apr-29

12:00

Apr-30

00:00

Apr-30

12:00

Power (GW)

Date

Curtailment

Wind

PV

Gas CT

Gas CC

Hydropower

CSP

Biopower

Coal

Geothermal

Nuclear

Shifted Load

Load
Renewable Electricity Futures Study — Executive Summary

22 

Additional challenges to power system planning and operation would arise in a high renewable 

electricity future, including management of low-demand periods and curtailment of excess 

electricity generation. The hourly analysis also found that, in contrast to today’s fossil-fueldominated electricity system for which the time of peak load (e.g., summer afternoons) is of 

most concern, operational challenges for high renewable generation scenarios were most acute 

during low-demand periods (e.g., spring evenings) when the abundance of renewable supply 

relative to demand would force thermal generators to cycle or ramp down to their minimum 

generation levels.31 During low-demand periods in today’s system and in the baseline scenario, 

most of the peaking needs are met with hydropower and combined cycle units; combustion 

turbines are needed but to a much lesser extent than in the summer. Although the load 

characteristics in 2050 are similar in the baseline scenario and the high renewable scenarios, 

during low-demand periods in the latter (e.g., Figure ES-6[b]), there was enough aggregate 

renewable electricity to fully serve load, causing the net load (load minus variable wind and PV 

generation) to be much more variable compared to the rest of the year. This increased variability 

in net load creates challenges associated with greater power plant cycling and ramping. 

A primary challenge of variable renewable energy integration at higher levels of penetration is 

the need at times to curtail excess electricity, particularly during periods with low electricity 

demands.32 The hourly dispatch analysis estimated that overall in 2050, 8%–10% of wind, solar, 

and hydropower generation would need to be curtailed under an 80%-by-2050 RE scenario. 

Curtailments reduce capacity factors and introduce uncertainty in electricity sales, thereby 

negatively impacting plant economics. A variety of technical and institutional approaches could 

be applied to reduce these levels of curtailment. First, additional transmission capacity in 

congested corridors would help alleviate congestion and reduce curtailment. Second, increasing 

the size of reserve-sharing groups could help reduce the number of inflexible generators online to 

provide spinning reserves; curtailment of renewable generation could be reduced if fewer plants 

operate at minimum levels. Third, the flexibility of the thermal fleet could be improved, or 

market structures could be implemented to encourage the operation of more flexible generators. 

Fourth, additional energy storage and controllable loads could be used to improve system 

flexibility. Finally, new or existing industries could take advantage of the low-cost electricity 

available during seasons or times when curtailment would have occurred, and the resulting 

increased demand could then consume electricity that otherwise would have been curtailed. 

Electric sector modeling shows that a more flexible system is needed to accommodate increasing 

levels of renewable generation. System flexibility can be increased using a broad portfolio of 

supply- and demand-side options and will likely require technology advances, new operating 

procedures, evolved business models, and new market rules. As renewable electricity generation

increased from 20% in the baseline scenario to 90% in the exploratory scenarios, the annual 

contribution from variable generation (wind and solar PV) grew from 7% to 48% in 2050. At 

 

31 Peak load still requires management and will be challenging for the same reasons it is today, but in addition, 

management of low-demand periods and curtailment will be required with high variable renewable electricity. 32 This situation parallels the use of combustion turbines in conventional systems, which are typically used just a few 

hundred hours per year to meet summer peak loads and are largely idle much of the rest of the year. As such, both 

the conventional and the high renewable electricity systems operate with excess capacity most of the time. While the 

high renewable system generates power with the excess capacity as long as resources are available, the conventional 

system simply leaves the excess capacity idle.
Renewable Electricity Futures Study — Executive Summary

23 

this high level of variable generation, ensuring a real-time balance between electricity supply and 

demand is more challenging The variability and uncertainty associated with these high levels of 

wind and PV penetration were found to be manageable through the application of adequate 

flexible generation capacity, the use of grid storage and demand-side technologies, the expansion 

of transmission infrastructure, and greater conventional plant dispatch flexibility, including 

significant daily ramping of fossil generators. (Dispatchable renewable technologies, like 

conventional technologies, do not impose significant additional challenges to system operability, 

and they are also used to help manage wind and solar PV integration.) 

The RE Futures analysis considers reserves necessary for reliable electric system operations, 

spanning a wide range of timescales (from long-term planning reserves to short-term operating 

reserves). The same capacity reserve margin requirements were satisfied across all scenarios 

despite the relatively low capacity values of variable resources and their increasing deployment 

as renewable penetration increased. Partly to satisfy planning reserve requirements, greater 

aggregate capacity was needed in high penetration renewable scenarios (see Figure ES-3).

Additional operating reserves were also found to be required in high variable renewable 

generation systems and were accommodated through the availability of conventional power 

plants, storage technologies, and demand-side practices. The analysis included multiple 

components of operating reserves, namely contingency reserves, frequency regulation reserves, 

and reserves associated with imperfect forecasts of wind and PV generation. Figure ES-7 shows 

how operating reserve requirements increased as renewable deployment increased and the

different options used to meet these requirements in the exploratory scenarios.33 Although 

operating reserve requirements increase with wind and PV deployment (due to greater forecast 

errors), because the dispatch of existing conventional power plants declines to accommodate 

additional wind and PV generation, these existing conventional units were found to be more 

available to satisfy the necessary operating reserve requirements. In other words, a high 

renewable electricity future would reduce the energy-providing role of the conventional fleet and 

increase its reserve-providing role. 

The analysis found use of storage to be an attractive option to increase electric system flexibility 

due to the ability of storage to shift load to better correlate with output from variable generators, 

reduce curtailments by storing excess generation in times of low demand, and provide firm 

capacity for a variety of reserve services. In the core 80% RE scenarios, for example, storage 

deployment was found to increase from approximately 20 GW in 2010 to 100–152 GW in 2050. 

Demand-side options were also found to play a significant role in meeting the integration 

challenges of a high renewable electricity future. For example, in the core 80% RE scenarios, 

28–48 GW of demand-side interruptible load were deployed in 2050, compared with just 15.6 

GW deployed in 2009. 

 

33 In Figure ES-7, the total contribution to operating reserves exceeds the requirement due to the fact that only one 

time (summer peak) is shown, while certain reserve-types (e.g., interruptible load) are annual in nature and deployed 

to serve other times not shown. 
Renewable Electricity Futures Study — Executive Summary

24 

(a) 2050 operating reserve requirement during 

the summer peak by reserve type

(b) 2050 contributions toward total operating 

reserve requirement by technology type

Figure ES-7. Operating reserve requirements as renewable electricity levels increase

The RE Futures analysis suggests that variable generation levels of up to nearly 50% of annual 

electricity can be accommodated when a broad portfolio of supply- and demand-side flexibility 

resources is available at a level substantially higher than in today’s electricity system. A broad 

portfolio of flexible supply- and demand-side resources and options were made available in the 

scenario modeling, and were relied upon particularly in the high renewable generation scenarios, 

including: 

• Maintaining sufficient capacity on the system for planning reserves

• Relying on demand-side interruptible load, conventional generators (particularly natural 

gas generators), and storage to manage increased operating reserve requirements

• Mitigating curtailment with storage and controlled charging of electric vehicles 

• Operating the system with greater conventional power plant ramping 

• Relying on the dispatchability of certain renewable technologies (e.g., biopower, 

geothermal, CSP with storage and hydropower) 

• Leveraging the geospatial diversity of the variable resources to smooth output ramping 

• Transmitting greater amounts of power over longer distances to smooth electricity 

demand profiles and meet load with remote generation 
Renewable Electricity Futures Study — Executive Summary

25 

Achieving the system flexibility required to integrate high levels of renewable generation will 

require some combination of technology advances, new operating procedures, evolved business 

models, and new market rules. Although the analysis does not examine how these mechanisms 

could be implemented, it does describe the power system flexibility characteristics needed for the 

integration of high levels of renewable generation. 

Transmission Expansion in High Renewable Electricity Futures

As renewable electricity generation increases, additional transmission infrastructure is required 

to deliver generation from cost-effective remote renewable resources to load centers, enable 

reserve sharing over greater distances, and smooth output profiles of variable resources by 

enabling greater geospatial diversity. Many of the system flexibility resources and options 

described above can benefit from transmission infrastructure enhancements to enable the transfer 

of power and sharing of reserves over large areas to accommodate the variability of wind and 

solar electricity generation in combination with variability in electricity demand. With high 

penetrations of variable generation, net load (load minus variable generation) in a specific region 

can show dramatic ramps. Transmission between regions helps reduce ramps in net load because 

it allows system operators to access a larger pool and more diverse mix of variable generation, 

with some smoothing of output profiles and demand profiles over larger geographic areas. Figure 

ES-8 shows projected new transmission capacity deployed over the 40-year study period for the 

exploratory scenarios. Demands for new transmission capacity are much greater in the higher 

renewable generation scenarios than in lower renewable generation scenarios, outstripping the 

effects of the low-demand assumption, reductions in transmission use by conventional fossil 

generation (freeing up the lines for renewable generation), and deployment of renewable 

resources that are proximate to load centers (e.g., PV and offshore wind).34 The increase in 

transmission needs as renewable electricity supply grows, for all 80%-by-2050 renewable 

electricity scenarios, result in an average annual projected transmission and interconnection 

investment that is within the recent historical range for total investor-owned utility transmission 

expenditures in the United States (i.e., $2 billion/yr to $9 billion/yr from 1995 through 2008) 

(Pfeifenberger et al. 2009). 

 

34 The analysis assumed that the existing transmission infrastructure is operational throughout the study period and 

did not consider maintenance needs for the existing transmission lines or other infrastructure. In addition, the 

analysis did not consider distribution-level maintenance or upgrades.
Renewable Electricity Futures Study — Executive Summary

26 

Figure ES-8. New transmission capacity requirements in the baseline and exploratory scenarios

Existing total transmission capacity in the contiguous United States is estimated at 150–200 million

MW-miles35

New transmission in the high renewable electricity scenarios was found to be concentrated in the 

middle and southwestern regions of the United States, mainly to access the high-quality wind 

and solar resources in those regions and to deliver generation from those resources to load 

centers. For example, Figure ES-9 presents a conceptual map of new transmission infrastructure 

needed in an 80%-by-2050 scenario. As shown in Figure ES-9 and quantified in Figure ES-8, the 

current isolation of the three asynchronous interconnections—Western Electricity Coordinating 

Council (WECC), Electric Reliability Council of Texas (ERCOT), and Eastern 

Interconnection—was greatly reduced in many of the high renewable electricity scenarios 

through the expansion of AC-DC-AC interties. This expansion enabled the East to have greater 

access to the high-quality renewable resources located in the western United States, although the 

hourly simulations and DC transmission power flow analysis suggests that these east-west 

transmission linkages were used bi-directionally to manage temporal variations in electricity 

supply and demand. Expanding interties between the three asynchronous interconnections was 

found to be desirable in many of the high renewable scenarios; however, results from the 

Constrained Transmission scenario showed that an 80%-by-2050 RE scenario was achievable 

even when such expansion was not allowed. 

Significant institutional obstacles, including constraints in siting new transmission lines, cost 

allocation concerns with transmission projects, and coordination between multiple governing 

entities, currently inhibit transmission expansion. The mechanisms to overcome these obstacles 

were not explored in the study, but the analysis demonstrates that additional long-distance 

transmission capacity can be an important characteristic of high renewable electricity futures.

 

35 The ReEDS model assumed 150 million MW-miles of existing inter-BA transmission capacity; the 200 million 

MW-mile estimate is from Homeland Security Infrastructure Database (2008) and other sources. 

0

20,000

40,000

60,000

80,000

100,000

0

50

100

150

200

250

Baseline30% RE40% RE50% RE60% RE70% RE80% RE90% RE

AC-DC-AC Intertie Capacity (MW)

Million MW-Miles

Percent RE

New Transmission New Intertie
Renewable Electricity Futures Study — Executive Summary

27 

Figure ES-9. New transmission capacity additions and conceptual location in the 80%

RE-ITI scenario 

Cost and Environmental Implications of High Renewable Electricity Futures

High renewable electricity futures can result in deep reductions in electric sector greenhouse 

gas emissions and water use. Direct environmental and social implications are associated with 

the high renewable futures examined, including reduced electric sector air emissions and water 

use resulting from reduced fossil energy consumption, and increased land use competition and 

associated issues. At 80% renewable electricity in 2050, annual generation from both coal-fired 

and natural gas-fired sources was reduced by about 80%, resulting in reductions in annual 

greenhouse gas emissions of about 80% (on a direct combustion basis and on a full life cycle 

basis) and in annual power sector water use of roughly 50%. At 80% renewable electricity, gross 

land-use impacts associated with renewable generation facilities, storage facilities, and 

transmission expansion totaled less than 3% of the land area of the contiguous United States.36

The direct incremental cost associated with high renewable generation is comparable to 

published cost estimates of other clean energy scenarios. Improvement in the cost and 

performance of renewable technologies is the most impactful lever for reducing this incremental 

cost. The retail electricity price implications estimated for the 80%-by-2050 RE scenarios are 

comparable to those seen in other studies with similarly transformative electricity futures, as 

shown on Figure ES-10. Low carbon and clean energy scenarios, evaluated by the U.S. Energy 

 

36 Net land-use impacts, considering the implications of reduced conventional generation, and land-use impacts 

based on disrupted lands, are both expected to be smaller. As an example of the latter case, disrupted land would 

generally be less than 5% of gross land area for wind generation facilities.
Renewable Electricity Futures Study — Executive Summary

28 

Information Administration (EIA) and the U.S. Environmental Protection Agency (EPA), with 

avoided carbon emissions trajectories similar to the core 80% RE scenarios showed increases in 

average retail electricity prices (relative to their own reference scenarios) in 2030 of $9–

$26/MWh, rising to $41–$53/MWh by 2050. These studies generally considered a portfolio of 

clean generation technology options, including renewable, nuclear, and low emissions fossil. The 

estimated incremental price impacts of the core 80% RE scenarios are comparable to these 

estimates.

Figure ES-10. Average increase in retail electricity rates relative to

study-specific reference/baseline scenarios

EIA 2011a and 2011b document analysis of clean energy scenarios. EIA 2009, EPA 2009, EIA 2010, and 

EPA 2010 report on analysis of several low carbon emissions scenarios.

As with these other clean generation scenarios that would represent a nearly wholesale 

transformation of the U.S. electricity system, the high renewable generation scenarios examined 

show a direct incremental cost relative to the continued evolution of today’s conventional 

generation-dominated system. Higher electricity prices associated with the high renewable

scenarios are driven by replacement of existing generation plants with new generators (mostly 

renewable); additional balancing requirements reflected in expenditures for combustion turbines, 

storage, and transmission; and the assumed higher relative capital cost of renewable generation, 

compared to conventional technologies, assumed in the analysis. The increased capital 

investments associated with these drivers, compared to the baseline scenario, were not fully 

offset by cost savings associated with lower fossil energy consumption. The incremental cost 

does not include investments in energy efficiency implied by low electricity demand 

assumptions, or the savings in avoided generation resulting from these investments. Further, the 

incremental cost estimate does not consider indirect societal costs associated with the scenarios 

(e.g., associated with the greenhouse gas emissions described above), or economy-wide impacts.

$0

$10

$20

$30

$40

$50

$60

2010 2020 2030 2040 2050

Real 2009$/MWh

Year

Increase in retail electricity price relative to reference/baseline

Core 80% RE (ReEDS) EIA 2009c

EPA 2009a EIA 2010b

EPA 2010 EIA 2011a

EIA 2011b
Renewable Electricity Futures Study — Executive Summary

29 

Advancements in renewable technologies, reflected by technology cost and performance 

improvement assumptions, had the greatest impact on the incremental cost of the high renewable 

generation scenarios. For example, the low end of the range of incremental electricity price 

shown in Figure ES-10 reflects the scenario with the highest assumed renewable technology 

improvement (RE-ETI), while the high end reflects the lowest technology improvement scenario 

(RE-NTI).37 Assumed system constraints had more modest impact on direct incremental costs; 

scenarios reflecting constraints to transmission expansion, renewable resources, and grid 

flexibility all had similar costs, which fell well within the bounds identified in Figure ES-10. 

Finally, incremental costs were largely insensitive to differences in projections for fossil fuel 

prices and fossil technology improvements. 

The lower renewable generation levels examined in the exploratory scenarios showed lower 

incremental 2050 retail electricity prices. For example, the 30% RE scenario under highest 

technology improvement assumptions (RE-ETI) showed no price increase in 2050 relative to the 

baseline scenario (which used RE-ITI assumptions). This result suggests that significant 

expansion of renewable generation beyond the 2010 level (10% of total generation) could be 

achieved with little or no incremental cost, assuming evolutionary improvements in renewable 

technologies. 

There are significant inherent uncertainties with respect to future electricity demand, technology 

improvements, fossil energy prices, social and institutional choices, and regulatory and 

legislative actions related to the scenarios examined that, in turn, contribute to significant 

uncertainty in the implications reported above. Further, there are a variety of indirect (or 

downstream) implications that may result from the direct electric sector cost, environmental, and 

social implications identified. For example, incremental investment in generation capacity and 

associated infrastructure will have implications related to economic activity and employment in 

the energy industry. Reductions in fossil energy consumption will have environmental 

implications beyond air emissions, including implications related to water quality, terrestrial and 

marine contamination, and waste disposal, not only associated with electricity generation 

facilities but also for activities related to fuel extraction and transportation. Further, air emissions 

reductions will have implications for human health and climate change. Identification, and in 

some cases quantification, of these indirect implications is an active area of wide-ranging 

research. This analysis does not attempt to evaluate these indirect impacts of high renewable 

electricity futures. Further research is critically needed to systematically assess the relative 

impacts of different forms of energy supply in the context of a robust comprehensive framework 

that assesses both direct and indirect impacts. Such research could inform national energy policy 

decisions as well as local siting and permitting processes related to proposed generation facilities 

and supporting infrastructure. 

Effects of Demand Growth on High Renewable Electricity Futures

With higher electricity demand growth, high levels of renewable generation present increased 

resource and grid integration challenges. RE Futures did not explicitly evaluate the cost 

effectiveness of energy efficiency adoption compared with supply-side options. However, the 

 

37 The RE-ETI assumptions are based on evolutionary improvements to currently commercial technologies and do 

not reflect DOE activities to further lower renewable technology costs so that they achieve parity with conventional 

technologies.
Renewable Electricity Futures Study — Executive Summary

30 

analysis suggests that under a high-demand scenario, greater and more rapid deployment of 

renewable and other supply- and demand-side technologies would be required. For example, 

while 32–46 GW/yr of renewable capacity additions were estimated from 2041 to 2050 in the 

low-demand core 80% RE scenarios, approximately 66 GW/yr would be needed during the same 

time period under a more-traditional, higher-demand trajectory. The analysis also found that in 

the 80%-by-2050 renewable electricity high-demand scenario, variable resources (wind and PV) 

were deployed to a greater extent in absolute and percentage terms than they were in the lowdemand scenarios due to the greater resource available for wind and solar generation compared 

with other forms of renewable generation. As a consequence, additional flexible supply- and 

demand-side technologies, such as storage facilities, natural gas combustion turbine power 

plants, and interruptible load, were deployed and greater transmission expansion was needed to 

connect remotely located renewable resources of all types. 

Higher end-use electricity demand increased the environmental impacts from the electric sector, 

such as greater greenhouse gas emissions, water use for thermoelectric cooling, and land use. In 

addition, higher demand growth also resulted in a greater increase in electricity prices. For 

example, in the High-Demand 80% RE scenario, the average annual retail electricity price 

increased by 1.3% per year (2011–2050, in real dollar terms) compared with 1.1% per year in the 

(low-demand) 80% RE-ITI scenario.38 The increase in retail electricity prices driven by higher 

demand growth is not restricted to the high renewable penetration scenarios; it is evident under 

the baseline scenario as well. In particular, the average annual retail electricity price increased by 

0.6% per year (2011–2050, in real dollar terms) in the High-Demand Baseline scenario 

compared with 0.3% per year in the Low-Demand Baseline scenario. While these results indicate 

that higher demand growth would lead to greater electricity price increases, they also 

demonstrate that the direct incremental costs associated with high renewable generation levels 

actually decreased under higher demand growth. 

Conclusions

The RE Futures study assesses the extent to which future U.S. electricity demand could be 

supplied by commercially available renewable generation technologies—including wind, utilityscale and rooftop PV, CSP, hydropower, geothermal, and biomass—under a range of 

assumptions for generation technology improvement, electric system operational constraints, and 

electricity demand. Within the limits of the tools used and scenarios assessed, hourly simulation 

analysis indicates that estimated U.S. electricity demand in 2050 could be met with 80% of 

generation from renewable energy technologies with varying degrees of dispatchability together 

with a mix of flexible conventional generation and grid storage, additions of transmission, more 

responsive loads, and foreseeable changes in power system operations. While the analysis was 

based on detailed geospatially rich modeling down to the hourly timescale, the study is subject to 

many limitations both with respect to modeling capabilities and the many assumptions required 

about inherently uncertain variables, including future technological advances, institutional 

choices, and market conditions. Nonetheless, the analysis shows that realizing this significant 

transformation of the electricity sector would require:

 

38 To isolate the effect of demand growth, the High-Demand 80% RE Scenario is compared with the 80% RE-ITI 

scenario since they both relied on the same technology improvement projection and used the same assumptions 

related to transmission, system flexibility, and renewable resources.
Renewable Electricity Futures Study — Executive Summary

31 

• Sustained build-up of many renewable resources in all regions of the United States

• Deployment of an appropriate mix of renewable technologies from the abundant and 

diverse U.S. renewable resource supply in a way that accommodates institutional or 

operational constraints to the electricity system, including constraints to transmission 

expansion, system flexibility, and resource accessibility

• Establishment of mechanisms to ensure adequate contribution to planning and operating 

reserves from conventional generators, dispatchable renewable generators, storage, and 

demand-side technologies 

• Increasing the flexibility of the electric system through the adoption of some combination 

of storage technologies, demand-side options, ramping of conventional generation, more 

flexible dispatch of conventional generators, energy curtailment, and transmission 

• Expansion of transmission infrastructure to enable access to diverse and remote resources 

and greater reserve sharing and balancing over larger geographic areas. 

These general requirements indicate that many aspects of the electric system may need to evolve 

substantially for high levels of renewable electricity to be deployed. Significant further work is 

needed to improve the understanding of this potential evolution, such as the following: 

• A comprehensive cost-benefit analysis to better understand the economic and 

environmental implications of high renewable electricity futures relative to today’s 

electricity system largely based on conventional technologies and alternative futures in 

which other sources of clean energy are deployed at scale

• Further investigation of the more complete set of issues around all aspects of power 

system reliability because RE Futures only partially explores the implications of high 

penetrations of renewable energy for system reliability

• Improved understanding of the institutional challenges associated with the integration of 

high levels of renewable electricity, including development of market mechanisms that 

enable the emergence of flexible technology solutions and mitigate market risks for a 

range of stakeholders, including project developers 

• Analysis of the role and implications of energy research and development activities in 

accelerating technology advancements and in broadening the portfolio of economically 

viable future renewable energy supply options and supply- and demand-side flexibility 

tools. 
Renewable Electricity Futures Study — Executive Summary

32 

Appendix. Project Participants and Contributors

The National Renewable Energy Laboratory coordinated preparation of the RE Futures report, 

which is the culmination of contributions from more than 110 individuals and more than 35 

organizations representing industry, utilities, universities, electric system operators and 

transmission organization, energy regulators, the government, and other sectors. The Project 

Leaders regret the inadvertent omission of any project participants and contributors, whether 

their input to the project involved contributing to project design, conducting analysis, authoring 

or contributing content, reviewing manuscript drafts, or producing the report. 

Project Sponsor

Sam Baldwin U.S. Department of Energy 

Project Leaders

Maureen Hand National Renewable Energy Laboratory 

Edgar DeMeo Renewable Energy Consulting Services, Inc. 

James Newcomb National Renewable Energy Laboratory, formerly

Gian Porro National Renewable Energy Laboratory 

John M. Reilly Massachusetts Institute of Technology

Project Steering Committee Members

Douglas Arent, Chair National Renewable Energy Laboratory 

Jessica Bian North American Electric Reliability Corporation

Aaron Bennett* North American Electric Reliability Corporation

Mark Brownstein Environmental Defense Fund

Nils Mellquist Deutsche Asset Management

Clark W. Gellings Electric Power Research Institute

Kurt J. Haeger Xcel Energy

John (Skip) Laitner American Council for an Energy-Efficient Economy

Douglas Larson Western Interstate Energy Board 

James Lyons Novus Energy Partners 

Ben Paulos Energy Foundation 

Katie McCormack* Energy Foundation 

Mark O'Malley University College Dublin

Dale W. Osborn Midwest Independent System Operator

Frederick Weston The Regulatory Assistance Project

Project Steering Committee Observers

David Andrejcak Federal Energy Regulatory Commission 

Sasan Jalali Federal Energy Regulatory Commission 

Dharmendra (Dave) Sharma Federal Energy Regulatory Commission 

Monica Taba Federal Energy Regulatory Commission 

Mary Beth Tighe Federal Energy Regulatory Commission 

Eric Sedina Federal Energy Regulatory Commission 
Renewable Electricity Futures Study — Executive Summary

33 

Sam Baldwin U.S. Department of Energy 

Larry Mansueti U.S. Department of Energy 

David Meyer U.S. Department of Energy 

John Schnagle U.S. Department of Energy 

Matt Clouse U.S. Environmental Protection Agency * Alternate for organization represented.

Report Editors

Maureen Hand National Renewable Energy Laboratory

Sam Baldwin U.S. Department of Energy 

Edgar DeMeo Renewable Energy Consulting Services, Inc. 

John M. Reilly Massachusetts Institute of Technology 

Trieu Mai National Renewable Energy Laboratory 

Douglas Arent National Renewable Energy Laboratory 

Gian Porro National Renewable Energy Laboratory 

Mike Meshek National Renewable Energy Laboratory 

Debra Sandor National Renewable Energy Laboratory 

Report Authors and Contributors

For each volume, chapter, or appendix, lead authors are shown in bold. Authors are listed in 

italics. All others listed were contributors to the report.

Volume 1. Exploration of High-Penetration Renewable Electricity Futures 

For the suggested citation of Volume 1, see the title page of this volume. 

Executive Summary

Trieu Mai National Renewable Energy Laboratory 

Debra Sandor National Renewable Energy Laboratory 

Ryan Wiser Lawrence Berkeley National Laboratory

Thomas Schneider National Renewable Energy Laboratory 

Introduction, Chapter 1–5, and Conclusions

Trieu Mai National Renewable Energy Laboratory 

Ryan Wiser Lawrence Berkeley National Laboratory

Gregory Brinkman National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

Donna J. Hostick Pacific Northwest National Laboratory

Debra Sandor National Renewable Energy Laboratory 

Galen Barbose Lawrence Berkeley National Laboratory

Naim Darghouth Lawrence Berkeley National Laboratory

Easan Drury National Renewable Energy Laboratory 

Erik Ela National Renewable Energy Laboratory 

Jeffrey Logan National Renewable Energy Laboratory 

Matthew Mowers National Renewable Energy Laboratory, formerly 

Walter Short National Renewable Energy Laboratory, formerly 

Patrick Sullivan National Renewable Energy Laboratory 
Renewable Electricity Futures Study — Executive Summary

34 

Lan Trinh ABB

Ethan Warner National Renewable Energy Laboratory 

Mary Werner National Renewable Energy Laboratory 

Jinxiang Zhu ABB

Appendix A. Implications of High-Penetration Renewable Electricity Futures

Ryan Wiser Lawrence Berkeley National Laboratory

Trieu Mai National Renewable Energy Laboratory 

Naim Darghouth Lawrence Berkeley National Laboratory

Paul Denholm National Renewable Energy Laboratory 

Garvin Heath National Renewable Energy Laboratory 

Gian Porro National Renewable Energy Laboratory 

Adam Schlosser Massachusetts Institute of Technology

Ken Strzepek Massachusetts Institute of Technology

Jonathan Baker Massachusetts Institute of Technology, formerly 

Galen Barbose Lawrence Berkeley National Laboratory

Jordan Macknick National Renewable Energy Laboratory 

Andrew Mills Lawrence Berkeley National Laboratory 

Jon Pietruszkiewicz Black & Veatch

Debra Sandor National Renewable Energy Laboratory 

Appendix B. Models Used in RE Futures

Gregory Brinkman National Renewable Energy Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Appendix C. Methods for Estimating Life Cycle GHG Emissions for RE Futures Scenarios 

and Discussion of Limitations

Garvin Heath National Renewable Energy Laboratory 

Stacey Dolan National Renewable Energy Laboratory, formerly 

John Burkhardt National Renewable Energy Laboratory, formerly 

Elliot Cohen National Renewable Energy Laboratory, formerly 

Margaret Mann National Renewable Energy Laboratory 

Patrick O’Donoughue National Renewable Energy Laboratory 

Pamala Sawyer National Renewable Energy Laboratory, formerly 

Martin Vorum National Renewable Energy Laboratory 

Ethan Warner National Renewable Energy Laboratory 

Appendix D. Project Participants and Contributors

The Project Leaders compiled and reviewed this appendix of project participants and 

contributors. 
Renewable Electricity Futures Study — Executive Summary

35 

Volume 2. Renewable Electricity Generation and Storage Technologies

For suggested citations of Volume 2 and the chapters within it, see the title page of Volume 2. 

Introduction

Debra Sandor National Renewable Energy Laboratory 

Chapter 6. Biopower Technologies

Richard Bain National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

Garvin Heath National Renewable Energy Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Mark Downing Oak Ridge National Laboratory 

Scott Haase National Renewable Energy Laboratory 

Jordan Macknick National Renewable Energy Laboratory 

Margaret Mann National Renewable Energy Laboratory 

Dave O'Connor Electric Power Research Institute

Robert Perlack Oak Ridge National Laboratory 

Chapter 7. Geothermal Technologies

Chad Augustine National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

Garvin Heath National Renewable Energy Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Katherine Young National Renewable Energy Laboratory 

Arlene Anderson U.S. Department of Energy 

Jordan Macknick National Renewable Energy Laboratory 

Clay Nichols U.S. Department of Energy 

Greg Stillman U.S. Department of Energy 

Chapter 8. Hydropower Technologies

Douglas G. Hall Idaho National Laboratory

Norman A. Bishop Knight Piésold and Co. 

Glenn F. Cada Oak Ridge National Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Stephen R. Brown HDR|DTA

Jordan Macknick National Renewable Energy Laboratory 

Chapter 9. Ocean Energy Technologies

Robert Thresher National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

George Hagerman Virginia Polytechnic Institute and State University

Garvin Heath National Renewable Energy Laboratory 

Sean O’Neil Ocean Renewable Energy Coalition

Joshua Paquette Sandia National Laboratories 
Renewable Electricity Futures Study — Executive Summary

36 

Debra Sandor National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Chapter 10. Solar Energy Technologies

Easan Drury National Renewable Energy Laboratory 

Robert Margolis National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

Alan C. Goodrich National Renewable Energy Laboratory 

Garvin Heath National Renewable Energy Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Michael Coddington National Renewable Energy Laboratory 

Barry Friedman National Renewable Energy Laboratory 

Jordan Macknick National Renewable Energy Laboratory 

Mark Mehos National Renewable Energy Laboratory 

Craig Turchi National Renewable Energy Laboratory 

Chapter 11. Wind Energy Technologies

Jamie Chapman Vestas Wind Systems/Texas Tech University

Eric Lantz National Renewable Energy Laboratory 

Paul Denholm National Renewable Energy Laboratory 

Fort Felker National Renewable Energy Laboratory 

Garvin Heath National Renewable Energy Laboratory 

Trieu Mai National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Jordan Macknick National Renewable Energy Laboratory 

Craig Mataczynski RES Americas

Andrew Oliver RES Americas

Paul Veers Sandia National Laboratories/National Renewable 

Energy Laboratory 

Lawrence D. Willey General Electric/Clipper Windpower 

Ryan Wiser Lawrence Berkeley National Laboratory 

Chapter 12. Energy Storage Technologies

Paul Denholm National Renewable Energy Laboratory 

Steven J. Fernandez Oak Ridge National Laboratory

Douglas G. Hall Idaho National Laboratory

Trieu Mai National Renewable Energy Laboratory 

Suzanne Tegen National Renewable Energy Laboratory

Chaitanya Baone Oak Ridge National Laboratory 

Norman A. Bishop Knight Piésold 

Stanton W. Hadley Oak Ridge National Laboratory 

John D. Kueck Oak Ridge National Laboratory 

Appendix E. Supplemental Information for Biopower Technologies

Richard Bain National Renewable Energy Laboratory 
Renewable Electricity Futures Study — Executive Summary

37 

Appendix F. Supplemental Information for Wind Energy Technologies

Jamie Chapman Vestas Wind Systems/Texas Tech University

Eric Lantz National Renewable Energy Laboratory 

Donna Heimiller National Renewable Energy Laboratory 

Jordan Macknick National Renewable Energy Laboratory 

Volume 3. Electricity Use in 2050

For the suggested citations of Volume 3, see the title page of Volume 3. 

Introduction, Chapters 12–20, and Conclusions

Donna J. Hostick Pacific Northwest National Laboratory

David B. Belzer Pacific Northwest National Laboratory

Stanton W. Hadley Oak Ridge National Laboratory 

Tony Markel National Renewable Energy Laboratory 

Chris Marnay Lawrence Berkeley National Laboratory

Michael Kintner-Meyer Pacific Northwest National Laboratory

Daryl R. Brown Pacific Northwest National Laboratory

Gonçalo Cardoso Lawrence Berkeley National Laboratory 

Peter Chan Lawrence Berkeley National Laboratory

James A. Dirks Pacific Northwest National Laboratory

Steven Doig Rocky Mountain Institute

Trucy Phan Lawrence Berkeley National Laboratory

Appendixes G–N 

Donna J. Hostick Pacific Northwest National Laboratory

David B. Belzer Pacific Northwest National Laboratory

Stanton W. Hadley Oak Ridge National Laboratory 

Tony Markel National Renewable Energy Laboratory 

Chris Marnay Lawrence Berkeley National Laboratory

Michael Kintner-Meyer Pacific Northwest National Laboratory

Daryl R. Brown Pacific Northwest National Laboratory

Gonçalo Cardoso Lawrence Berkeley National Laboratory

Peter Chan Lawrence Berkeley National Laboratory

Trucy Phan Lawrence Berkeley National Laboratory

Volume 4. Bulk Electric Power System Operations Strategies and Transmission Planning

For the suggested citations of Volume 4, see the title page of Volume 4. 

Introduction, Chapters 21–25, and Conclusions

Michael Milligan National Renewable Energy Laboratory 

Erik Ela National Renewable Energy Laboratory 

Jeff Hein National Renewable Energy Laboratory, formerly 

Thomas Schneider National Renewable Energy Laboratory 

Gregory Brinkman National Renewable Energy Laboratory

Paul Denholm National Renewable Energy Laboratory

Jay Caspary Southwest Power Pool 

Lynn Coles National Renewable Energy Laboratory 
Renewable Electricity Futures Study — Executive Summary

38 

Brendan Kirby Consult Kirby 

Trieu Mai National Renewable Energy Laboratory 

Andrew Mills Lawrence Berkeley National Laboratory

J. Charles Smith Utility Wind Integration Group

Lan Trinh ABB

Report Coordinators, Technical Editors, Report Designers, and Report Producers

Mike Meshek, Report Coordinator National Renewable Energy Laboratory 

Debra Sandor, Report Coordinator National Renewable Energy Laboratory 

Jørn Aabakken National Renewable Energy Laboratory 

Joshua Bauer National Renewable Energy Laboratory 

Linda Bevard PWT Communications

Michelle Dorsett PWT Communications

Devin Egan National Renewable Energy Laboratory 

Josh Finn Black & Veatch

Bill Gillies National Renewable Energy Laboratory 

Scott Gossett National Renewable Energy Laboratory 

Sara Havig National Renewable Energy Laboratory 

Al Hicks National Renewable Energy Laboratory 

Jennifer Josey National Renewable Energy Laboratory 

Carol Kerstner National Renewable Energy Laboratory

Michelle Kubik National Renewable Energy Laboratory 

Cezanne Murphy-Levesque PWT Communications

Anthony Lopez National Renewable Energy Laboratory 

Mary Lukkonen National Renewable Energy Laboratory 

Jordan Macknick National Renewable Energy Laboratory 

Alexis Powers National Renewable Energy Laboratory 

Stephanie Price National Renewable Energy Laboratory 

Billy Roberts National Renewable Energy Laboratory 

Rachel Sullivan National Renewable Energy Laboratory 

Mark Swisher The Office of Mark Swisher

Lisa J. Teman All the Right Words

Patricia Weis-Taylor PWT Communications

Interim Review Meeting Facilitators

Jennifer Downes-Angus Energetics Incorporated 

Richard Scheer Energetics Incorporated

Peggy Welsh Energetics Incorporated 
Renewable Electricity Futures Study — Executive Summary

39 

Report Reviewers

Comments provided by reviewers represent only the opinions of the individual reviewers, 

and they do not imply agreement with the conclusions of the report. Reviewers did not help to 

draft the chapters they reviewed. Their participation is not meant to imply that they or their 

respective organizations either agree or disagree with the findings of the effort.

Mark Ahlstrom WindLogics 

Arlene Anderson U.S. Department of Energy 

Jay Apt Carnegie Mellon University

William Ball SOCO

Mike Bahrman ABB

Floyd Barwig New York State Department of Public Service

Roger Bedard private consultant 

David Bellman American Electric Power, formerly

Jessica Bian North American Electric Reliability Corporation

Doug Blankenship Sandia National Laboratories 

Matt Bowen U.S. Department of Energy 

John Boyes Sandia National Laboratories, retired

Gerry Braun University of California, Davis

Marilyn Brown Georgia Institute of Technology 

Ron Brown American Forest & Paper Association

Mark Brownstein Environmental Defense Fund

Caitlin Callaghan AAAS Fellow at the U.S. Department of Energy 

Echo Cartwright New York Independent System Operator 

Gerry Cauley North American Electric Reliability Corporation 

Luis Cerezo PGS

Steven G. Chalk U.S. Department of Energy 

Robert Charles Sargent & Lundy

Kerry Cheung AAAS Fellow at the U.S. Department of Energy 

Helena Chum National Renewable Energy Laboratory 

Charlton Clark U.S. Department of Energy 

Steve Clemmer Union of Concerned Scientists 

Matt Clouse Environmental Protection Agency

Jessica Collins Xcel Energy

James Critchfield U.S. Environmental Protection Agency 

Matt Crozat U.S. Department of Energy 

Mike DeAngelis Sacramento Municipal Utility District

Paul DeCotis Long Island Power Authority 

John DeFusco Babcock & Wilcox Company 

Chris DeMarco University of Wisconsin–Madison

Joseph (Phil) Dipietro U.S. Department of Energy 

Ron DiPippo University of Massachusetts Dartmouth

Wayne Dyok Tetra Tech

Joseph Eto Lawrence Berkeley National Laboratory 

Phil Farese National Renewable Energy Laboratory 

Ronald Flood APS (Arizona Public Service)
Renewable Electricity Futures Study — Executive Summary

40 

Suresh Garimella Purdue University 

Bobi Garrett National Renewable Energy Laboratory 

Clark Gellings Electric Power Research Institute

Eric Gimon AAAS Fellow at the U.S. Department of Energy 

Avi Gopstein U.S. Department of Energy 

Jason Grumet Bipartisan Policy Center

Bryan Hannegan Electric Power Research Institute

Zia Haq U.S. Department of Energy 

Liangying Lynn Hecker MISO (Midwest Independent Transmission System 

Operator) 

Mike Henderson ISO New England

Michael Hogan European Climate Foundation 

Douglas Hollett U.S. Department of Energy 

Brian Holmes University College Cork

John Holmes University of Oxford, U.K., and European Academies 

Science Advisory Council Energy Programme 

(EASAC-EP)

John Huckerby Aotearoa Wave and Tidal Energy Association

Keith Jamison Energetics Incorporated 

Henry Jeffrey University of Edinburgh 

Thomas Johansson Lund University 

Susanne Jones Pacific Northwest National Laboratory

Frederic Jouve EDF

Jordan Kislear U.S. Department of Energy 

Elmar Kriegler Potsdam Institute for Climate Impact Research

Robert Kondziolka Salt River Project

Sven Kullander Uppsala University, Sweden, and EASAC-EP

John “Skip” Laitner American Council for an Energy Efficient Economy 

Doug Larson Western Interstate Energy Board

Mark Lauby North American Electric Reliability Corporation

Elliott Levine U.S. Department of Energy 

Joshua Linn Massachusetts Institute of Technology, formerly

Robert Litwin Pratt & Whitney

Peter Lund Helsinki University, Finland, and EASAC-EP

John Lushetsky U.S. Department of Energy, formerly 

Seungwook Ma U.S. Department of Energy/American Association for 

the Advancement of Science 

Enzo Marano The Ohio State University

Ralph Masiello KEMA

Jim McCalley Iowa State University

Jeff Mechenbier PNM (Public Service of New Mexico)

Amir Mikhail Clipper Windpower 

Rick Miller HDR|DTA

JoAnn Milliken U.S. Department of Energy 

Natalie Mims Rocky Mountain Institute, formerly 

Roy Mink Mink GeoHydro 
Renewable Electricity Futures Study — Executive Summary

41 

Fred Moore Dow Chemical

Joe Morabito Alcatel-Lucent 

Andrew Munro Grant County Public Utility District

Kelly Murphy Electric Utility Consultants, Inc. (EUCI)

Jay Nathwani U.S. Department of Energy 

Robin Newmark National Renewable Energy Laboratory 

Bradley Nickell Western Electricity Coordinating Council 

David Olsen Western Grid Group 

Michael Ornetzeder Austrian Academy of Sciences, Austria, and EASACEP

Dale Osborn Midwest ISO

Christina Palmero New York State Department of Public Service

William Parks U.S. Department of Energy 

Jeff Peterson New York State Energy Research & Development 

Authority

John Peterson U.S. Department of Energy, formerly 

Cedric Philibert International Energy Agency 

Brian Polagye University of Washington 

Alojz Poredos University of Ljubljana, Slovenia, and EASAC-EP

Michael Power University College Dublin

Mirko Previsic RE Vision Consulting 

Veronika Rabl Vision & Results

Valerie Reed U.S. Department of Energy 

Brent Rice National Renewable Energy Laboratory 

Giorgio Rizzoni The Ohio State University

Curt Robinson Geothermal Resources Council

David Rosner Bipartisan Policy Center

Jurriaan Ruys McKinsey & Company

Kent Saathoff Electric Reliability Council of Texas

Doug Sabo U.S. Bureau of Reclamation 

Mike Sale MJ Sales Associates

Elizabeth Salerno American Wind Energy Association

John Scahill Thermal Biofuels Consultants 

Ferd Schuth Max-Planck-Institut fur Kohlenforschung, Germany & 

EASAC-EP

Timothy Skone U.S. Department of Energy 

J. Charles Smith Utility Variable Generation Integration Group 

Paul Smith University College Dublin

Steven J. Smith Pacific Northwest National Laboratory

Neil Snyder National Renewable Energy Laboratory 

Jeb Stenhouse U.S. Environmental Protection Agency 

Don Stevens Pacific Northwest National Laboratory

John Stough Exelon 

Morgan Summers U.S. Department of Energy 

Fred Tornatore TSS Consultants 

Jessica Trancik Massachusetts Institute of Technology
Renewable Electricity Futures Study — Executive Summary

42 

Rachel Tronstein U.S. Department of Energy 

Elaine Ulrich U.S. Department of Energy 

Eugenijus Uspuras Lithuanian Energy Institute, Lithuania, and EASAC-EP

Jan S. Vaagen IFT University of Bergen, Norway, and EASAC-EP

Carl VanSant HCI Partners

Uday Varadarajan Climate Policy Initiative

Luis Vega University of Hawaii

Vijay Vittal Arizona State University

James Walker enXco, Inc. 

Joy Wang Georgia Institute of Technology 

Yu Wang Georgia Institute of Technology 

Mike Weedall Bonneville Power Administration

Carl Weinberg Pacific Gas and Electric Company, retired

John Weyant Stanford University

Colin Williams U.S. Geological Survey 

Marshall Wise Pacific Northwest National Laboratory

Xiaojing Xun Georgia Institute of Technology 

Jose Zayas U.S. Department of Energy 

Ken Zweibel The George Washington University
Renewable Electricity Futures Study — Executive Summary

43 

References

Black & Veatch. (2012). Cost and Performance Data for Power Generation Technologies. 

Overland Park, KS: Black & Veatch. 

DOE. (2011). U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts 

Industry. R.D. Perlack and B.J. Stokes (Leads), ORNL/TM-2011/224. Oak Ridge, TN: ORNL. 

EIA. (2009). Energy Market and Economic Impacts of HR 2454, the American Clean Energy 

and Security Act of 2009. SR-OIAF/2009-05. Washington, DC: U.S. Energy Information 

Administration. http://www.eia.doe.gov/oiaf/servicerpt/hr2454/. Accessed January 26, 2012. 

EIA. (2010). Energy Market and Economic Impacts of the American Power Act of 2010. SROIAF/2010-01.Washington, DC: U.S. EIA. http://www.eia.doe.gov/oiaf/servicerpt/kgl/. 

Accessed January 27, 2012. 

EIA. (2011a). “Analysis of Impacts of a Clean Energy Standard as Requested by Chairman 

Bingaman.” Analysis and Projections. http://www.eia.gov/analysis/requests/ces_bingaman/. 

EIA. (2011b). “Analysis of Impacts of a Clean Energy Standard as Requested by Chairman 

Hall.” Analysis and Projections. http://www.eia.gov/analysis/requests/ces_hall/. 

EPA (U.S. Environmental Protection Agency). (2009). “EPA Analysis of the American Clean 

Energy and Security Act of 2009 H.R. 2454 in the 111th Congress.” Washington, DC: EPA 

Office of Atmospheric Programs. http://www.epa.gov/climatechange/economics/pdfs/ 

HR2454_Analysis.pdf. Accessed January 27, 2012. 

EPA. (2010). “EPA Analysis of the American Power Act in the 111th Congress.” Washington, 

DC: EPA Office of Atmospheric Programs. http://www.epa.gov/climatechange/economics/pdfs/ 

EPA_APA_Analysis_6-14-10.pdf. Accessed January 27, 2012. 

Pfeifenberger, J.; Fox-Penner, P.; Hou, D. (2009). “Transmission Investment Needs and Cost 

Allocation: New Challenges and Models.” http://www.brattle.com/_documents/UploadLibrary/ 

Upload823.pdf. Accessed January 27, 2010. 
National Renewable Energy Laboratory

15013 Denver West Parkway, Golden, CO 80401

303-275-3000 • www.nrel.gov

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy 

Operated by the Alliance for Sustainable Energy, LLC

NREL/TP-6A20-52409-ES • December 2012

Printed with a renewable-source ink on paper containing at 

least 50% wastepaper, including 10% post consumer waste.