In the coming decades, additions to US electricity generation capacity are predicted by the USA's Energy Information Administration to be lower than in the recent past. In EIA's Annual Energy Outlook 2015 Reference Case, which reflects current laws and policies but does not include EPA's proposed Clean Power Plan, total generating capacity (including end-use generators like rooftop solar panels) increases from 1065 GW in 2013 to 1261 GW in 2040. The amount of capacity added is more than three times the amount that is expected to retire, with 287 GW added and 90 GW retired.
Capacity additions to 2017, much of which is under construction now, average about 17 GW per year and about half are nonhydro renewable plants (mainly wind and solar) prompted by federal tax incentives and renewable portfolio standards. From 2018 to 2024, projected additions average less than 4 GW per year, as earlier planned additions are sufficient to meet most growth in electricity demand. From 2025 to 2040, additions - primarily natural gas-fired and renewable technologies - average 12 GW per year. For comparison, the figure for 2000 to 2013 averaged 26 GW.
Natural gas-fired plants account for 58% of the capacity additions to 2040, while renewables provide 38% and nuclear 3%. Natural gas-fired combined-cycle plants are relatively inexpensive to build in comparison with new coal, nuclear, or renewable technologies, and are generally more efficient to operate than existing steam plants that may be powered by natural gas, oil, or coal.
Renewable additions are aided in the near term by federal tax credits, and in the longer term by rising natural gas prices and state renewable targets. The 109 GW of renewable capacity additions in the Reference Case are primarily wind (49 GW) and solar (48 GW) technologies, including 31 GW of solar photovoltaic installations from rooftop and other distributed generation installations.
Nuclear additions total 9 GW, including 6 GW of plants currently under construction and 3 GW projected to come online after 2029. New coal plants total just 1 GW, as high construction costs and uncertainty about future limits on greenhouse gas emissions reduce their competiveness.
The analysis in the AEO 2015 includes several cases that examine different assumptions of macroeconomic growth, world oil prices, and higher oil and natural gas resource availability, which yield a range of projected capacity additions. Policies such as the proposed Clean Power Plan, or the continuation of tax credits for certain renewable energy technologies that are scheduled to expire under current law are also expected to have a significant effect on projected capacity additions and retirements.