The U.S. electricity sector has seen tremendous growth in the past 60 years. From 1949 to 2009, U.S. electricity consumption increased by a factor of 13. To meet this rising demand, the U.S has built vast amounts of new electricity generating infrastructure. The total U.S. installed capacity in 2009 was 998 GW, compared with just 65 GW in 1949.

Sources: U.S. Energy Information Administration. 2010. “Annual Electric Generator data.” Form EIA-860 Data Files.
U.S. Energy Information Administration. 2010. Electric Power Annual 2009. Washington, D.C.: U.S. Department of Energy, November 23.

Fossil fuel combustion harms air quality and human health. A 2010 study by the Clean Air Task Force estimated that air pollution from coal-fired power plants accounts for more than 13,000 premature deaths, 20,000 heart attacks, and 1.6 million lost workdays in the U.S. each year. The total monetary cost of these health impacts is over $100 billion annually.

Source: Schneider, C., and Jonathan Banks. 2010. The Toll From Coal: An Updated Assessment of Death and Disease from America’s Dirtiest Energy Source. Clean Air Task Force, September.

In 2005, half of U.S. water withdrawals were made by the electricity sector. A “business-as-usual” U.S. electricity future will increase reliance on large thermal power plants and keep water demands high.

Source: Kenny, J. F, N. L Barber, S. S Hutson, K. S Linsey, J. K Lovelace, and M. A Maupin. 2009. Estimated Use of Water in the United States 2005. Reston, Virginia: U.S. Geological Survey.

In Reinventing Fire, Rocky Mountain Institute investigates the implications of four radically different future electricity scenarios - from a “business-as-usual” case to a network of intelligent microgrids powered largely by distributed renewables.

Sources: Metz, B., O.R. Davidson, R. Bosch, and L.A. Meyer. 2007. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge: Cambridge University Press.
Peterson, Per. 2003. “Will the United States Need a Second Geologic Repository?” The Bridge, National Academy of Engineering 33 (3).
U.S. Energy Information Administration. 2010. Annual Energy Outlook 2010: WIth Projections to 2035. Washington, D.C.: U.S. Department of Energy, April.

While U.S. demand for electricity has risen in all but four years since 1949, the rate of increase has been steadily trending down. The Energy Information Administration predicts an annual growth rate around +1% to 2030 (which RMI extrapolates to 2050). Successfully implementing the energy efficiency improvements in buildings and industry discussed in Reinventing Fire could reduce this to a steady –1%.

Sources: U.S. Energy Information Administration. 2010a. Annual Energy Outlook 2010: WIth Projections to 2035. Washington, D.C.: U.S. Department of Energy, April.
U.S. Energy Information Administration. 2010b. Electric Power Annual 2009. Washington, D.C.: U.S. Department of Energy, November 23.

Rocky Mountain Institute’s four scenarios for the future U.S. electricity system ( detailed here ) all have markedly different projected CO2 emissions over the next 40 years.

Sources: Anon. 2007. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge: Cambridge University Press.
U.S. Energy Information Administration. 2009. Emissions of Greenhouse Gases in the United States 2008. Washington, D.C.: U.S. Department of Energy, December.

Rocky Mountain Institute’s four scenarios for the future U.S. electricity system ( detailed here ) all have very different requirements for an expanded transmission infrastructure.

Source: RMI analysis

The required generating capacity and its breakdown are very different in each of Rocky Mountain Institute’s four scenarios for the future U.S. electricity system.

Source: RMI analysis

Each of Rocky Mountain Institute’s four scenarios for the future U.S. electricity system (detailed here) will have a very different electricity generation mix.

Source: RMI analysis

While Rocky Mountain Institute’s four scenarios for the future U.S. electricity system have profoundly different resource portfolios, grid structures, environmental impacts, and risk, all the scenarios have very similar overall system costs.

Source: RMI analysis

In evaluating the future U.S. electricity system, Rocky Mountain Institute created capital cost projections for fossil and renewable generation technologies through 2050. Many newer technologies, such as concentrated solar power, solar photovoltaics, and battery storage, are projected to have rapidly declining capital costs in the next 40 years.

Sources: RMI analysis using learning curve theory, as detailed in these sources.

Renewable energy technologies have historically had higher capital costs than fossil-fueled power plants, but these costs are falling rapidly.

Sources: Bony, Lionel, Newman, Sam, and Doig, Stephen. 2010. Achieving Low-Cost Solar PV: Industry Workshop Recommendations for Near-Term Balance of System Cost Reductions. RMI.
Kota, Sridhar. 2011. personal communication with author. January 31.
Terra Magnetica. 2010. “Siemens Launches Permanent Magnet-Based Gearless Wind Turbine”. April 25. link
Wiser, Ryan, and Mark Bolinger. 2011. 2010 Wind Technologies Market Report. Lawrence Berkeley National Laboratory, June.

The solar photovoltaics industry has seen remarkable cost reductions over the past 35 years. PV module prices have declined so much that today non-module costs are the majority of total installed cost for utility-scale PV projects. These “balance of system” costs are primed for major reduction through smarter and smaller power electronics, streamlined installation technologies and processes, and project development approaches that leverage low-risk capital and better customer education.

Source: Bony, Lionel, Newman, Sam, and Doig, Stephen. 2010. Achieving Low-Cost Solar PV: Industry Workshop Recommendations for Near-Term Balance of System Cost Reductions. RMI.

Unlike solar and windpower, which have had orders-of-magnitude reduction in cost as experience and manufacturing have scaled, the cost of building a nuclear reactor has increased over time. A reactor ordered today is 5–8 times more expensive per watt of capacity than a reactor built in the 1970s.

Source: Koomey, J., and N.E. Hultman. 2007. “A Reactor-Level Analysis of Busbar Costs for US Nuclear Plants, 1970–2005.” Energy Policy 35 (11): 5630–42.

Nuclear power plants have a history of major cost overruns and missed deadlines. Of plants whose construction was started prior to 1977, the average actual construction costs were two to three times higher than the average projected cost. The average project was extended at least three years beyond its original completion date.

Source: Energy Information Administration. 1986. An Analysis of Nuclear Power Plant Construction Costs. Washington, D.C.: U.S. Department of Energy.

There are currently 308 GW of coal-fired capacity and 185 GW of gas-fired capacity in operation in the United States. Assuming normal operating lives, 95% of the coal capacity and 99% of the gas capacity will be retired by 2050.

Sources: U.S. Energy Information Administration. 2008. "Existing Electric Generating Units in the United States". Washington, D.C.: U.S. Department of Energy.
U.S. Energy Information Administration. 2009."New U.S. Electric Generating Units by Operating Company, Plant and Month". Washington, D.C.: U.S. Department of Energy, December.
U.S. Energy Information Administration. 2010. "New U.S. Electric Generating Units by Operating Company, Plant and Month". Washington, D.C.: U.S. Department of Energy, December.

Any electricity future dependent on significant coal or gas resources brings with it the added risk of fuel availability. The McKelvey diagram is a useful visualization for classifying resources by their degrees of geologic assurance and economic recoverability.

Source: McKelvey, V.E. 1972. “Mineral Resource Estimates and Public Policy.” American Scientist 60 (1): 32-40.

RMI’s Migrate scenario explores a U.S. grid relying on nuclear power for 36% of annual generation. The required ramp-up of nuclear power would generate around 160,000 tons of nuclear waste over the next 40 years.

Sources: Alvarez, Robert and Jan Beyea, et al. 2003. “Reducing the Hazards from Stored Spent Power-Reactor Fuel in the United States.” Science & Global Security 11 (1):1.
Energy Information Administration. 2002. Annual Spent Fuel Discharges and Burnup, 1968–2002. Washington, D.C.: U.S. Department of Energy.
Peterson, Per. 2003. “Will the United States Need a Second Geologic Repository?” The Bridge, National Academy of Engineering 33 (3).

RMI’s Migrate scenario explores a U.S. grid relying on nuclear power for 36% of annual generation. The required ramp-up of nuclear power would generate around 160,000 tons of nuclear waste over the next 40 years.

Sources: List of sources available here

Buildings or industrial facilities with both heating loads and electricity demand can typically benefit from combined heat and power (CHP) generation. This technology allows both heat and electricity to be produced at a marginal cost less than that of both produced separately.

Source: Based on example in: Masters, Gilbert. 2004. Renewable and Efficient Electric Power Systems. Hoboken, New Jersey: John Wiley and Sons, Inc.

Buildings or industrial facilities that operate combined heat and power (CHP) generators purchase a fuel (typically natural gas) and use it to generate electricity onsite, capturing the waste heat for the facility’s heating demands. Whether or not the operator can generate electricity cheaper than they can buy it is dependent on the current costs of fuel and electricity as well as the efficiency of their unit, and is quantified by the spark spread.

Source: U.S. Environmental Protection Agency. “Combined Heat and Power.”

By 2050, 50% of the U.S. vehicle fleet will be electrified —more than 150 million cars and light trucks in all. With an average battery pack size of 18.4 kWh, this would amount to nearly 2,900 GWh of energy storage capacity. The addition of such a large and potentially unpredictable load could present problems for grid management if electric vehicle charging is not handled effectively.

Sources: Kromer, Matthew, and John Heywood. 2007. Electric Powertrains: Opportunities and Challenges in the U.S. Light-Duty Vehicle Fleet. Laboratory for Energy and the Environment.
Lovins, Amory B., and David Cramer. 2004. “Hypercars, Hydrogen, and the Automotive Transition”. International Journal of Vehicle Design 35 (1): 50-85.
U.S. Energy Information Administration. 2010. Annual Energy Outlook 2010. Washington, D.C.: U.S. Department of Energy, April.

There is some uncertainty in the reliability of the U.S. electricity system in a “business-as-usual” case. Although the U.S. electricity grid has a proven track record with conventional generation mixes, outages and grid disturbances are on the rise.

Sources: North American Electric Reliability Corporation. 2011. “Events Analysis: System Disturbance Reports.”
U.S. Department of Energy. 2011. “Electric Disturbance Events (OE-417) Annual Summaries.” Office of Electricity Delivery & Energy Reliability.

Together, wind and solar will account for 71% of total U.S. installed capacity in 2050 in Rocky Mountain Institute’s Transform case, up from 4.4% in 2010. Along with hydro, geothermal, and biomass, renewables will meet more than 80% of 2050 U.S. electricity demand.

Sources: Ackerman, Thomas, and Poul Erik Morthorst. 2005. “Economic Aspects of Wind Power in Power Systems.” In Wind Power in Power Systems, 384-410. England: John Wiley and Sons, Ltd.
Exeter Associates, K. 2007. Review of International Experience Integrating Variable Renewable Energy Generation. California Energy Commission.
GE Energy. 2010. Western Wind and Solar Integration Study. Prepared for National Renewable Energy Laboratory.
Terra Magnetica. 2010. “Siemens Launches Permanent Magnet-Based Gearless Wind Turbine”. April 25.
U.S. Energy Information Administration. 2010. "Electric Power Annual 2009". Washington, D.C.: U.S. Department of Energy, November 23.
Wiser, Ryan, and Mark Bolinger. 2011. 2010 Wind Technologies Market Report. Lawrence Berkeley National Laboratory, June.
Xcel Energy. 2010. “Xcel Energy’s Wind Energy Program.” Presented to Wind Energy Prediction - Research and Development Workshop, May 11.

The dynamic nature of variable renewable resources presents challenges to conventional electricity system operations. Production from wind and solar resources, in particular, is both variable (fluctuating throughout the day according to availability of the “fuel”) and uncertain (weather forecasting is required and by definition is not always accurate).

Sources: RMI analysis based on:
Electric Reliability Council of Texas. 2004. “FERC Form No. 714-ERCOT.”
GE Energy. 2010. Western Wind and Solar Integration Study. National Renewable Energy Laboratory.

Production from wind and solar resources, in particular, is both variable and uncertain. However, with good resource and demand forecasting and high availability of flexible demand and supply side resources, it is possible to operate an electricity system reliably with a high percentage of variable renewable energy.

Sources: RMI analysis using data from:
Electric Reliability Council of Texas. 2004. “FERC Form No. 714-ERCOT."
GE Energy. 2010. Western Wind and Solar Integration Study. Report prepared for the National Renewable Energy Laboratory.
National Renewable Energy Laboratory. 2011a. National Solar Radiation Data Base 1991–2005 Update. National Renewable Energy Laboratory.

A load-duration curve is a useful tool for comparing the impacts of different renewable portfolios on the grid. In this Rocky Mountain Institute analysis of renewable adoption on the Electric Reliability Council of Texas (ERCOT) grid, a generation mix of 25% solar and 15% wind yields the flattest load-duration curve over the year.

Source: RMI analysis using data from: Electric Reliability Council of Texas. 2004. “FERC Form No. 714-ERCOT.”

Different renewable portfolio compositions place differing demands on the generation and storage resources of the grid. In hours when variable renewable supply is not enough to meet the full load, the remaining demand must be met with dispatchable generators. When variable renewable supply exceeds the full load, the excess renewable supply must be stored or curtailed. The frequency of over or under-supply is highly dependent on the amount and mix of variable renewables on a given system.

Source: RMI analysis using data from: Electric Reliability Council of Texas. 2004. “FERC Form No. 714-ERCOT.”

Bulk energy storage can be incredibly useful in integrating variable renewable generation and providing ancillary services to the grid. The ultimate application of a particular energy storage technology is largely determined by its discharge time.

Source: Electricity Storage Association. 2011. “Storage Technologies: Technology Comparison."

Recent studies evaluating the cost of integrating variable renewables that account for up to 30% of a system’s peak-load range from 0.1 to 1.0¢/kWh.

Sources: Acker, T. et al. 2007. Final Report: Arizona Publiuc Service Wind Integration Cost Impact Study. Northern Arizona University, September.
Electrotek Concepts. 2003. We Energies System Operations Impacts of Wind Generation Integration. Electrotek Concepts, Inc., March 10.
EnerNex Corporation. 2007. Final Report: Avista Corporation Wind Integration Study. EnerNex, March.
EnerNex Corporation, and Idaho Power. 2007. Operational Impacts of Integrating Wind Generation into Idaho Power’s Existing Resource Portfolio. EnerNex, October.
Pacificorp. 2010. Pacificorp 2010 Wind Integration Resource Study. Pacificorp, September 1.
WindLogics, Inc. 2006. Final Report: 2006 Minnesota Wind Integration Study Volume II - Characterizing the Minnesota Wind Resource. WindLogics, Inc., November 30.
Zavadil, R. M, and others. 2004. "Xcel Energy and the Minnesota Department of Commerce–Wind Integration Study–Final Report.” EnerNex and WindLogics Inc., September 28.
Zavadil, R.M. 2006. Final Report: Wind Integration Study for Public Service Company of Colorado. EnerNex, May 22.

Rocky Mountain Institute’s four scenarios for the future U.S. electricity system ( detailed here ) all have different penetrations of demand response programs.

Source: RMI analysis using data from: The Brattle Group, Freeman, Sullivan & Co., and Global Energy Partners, LLC. 2009. A National Assessment of Demand Response Potential. Federal Energy Regulatory Commission, June.