Power Sector Evolution
On this page:
- Installation of Pollution Controls
- Fleet Turnover
- Changes in Utilization of Existing Generation
- Reduced Demand Growth
- Looking Ahead
The United States electric power sector has changed significantly since the passage of the Clean Air Act Amendments of 1990. Since 1995, sulfur dioxide (SO2) emissions from power plants have fallen 95%, nitrogen oxides (NOX) emissions have fallen 89%, and carbon dioxide (CO2) emissions have fallen 25%. During this same period, total gross electricity generation from power plants increased by 13% as a result of increased electricity demand. To learn more about these trends, visit Power Plant Emission Trends and the Power Sector Programs Progress Report.
The following chart is interactive. Hover over the chart to see more details.
Over the past few decades, both market and regulatory forces have driven key changes in the electric power sector that account for most of the emissions reductions.
Emissions from power plants occur from the combustion of fossil fuels to generate electricity. In 2022, fossil fuels (including coal, oil, and natural gas) remained the most common energy sources for electricity production in the U.S. Information and resources on the impacts of SO2, NOX, mercury, and greenhouse gas emissions from combustion of fossil fuels can be found on the human health and environmental impacts webpage.
Installation of Pollution Controls
State of the art pollution controls such as flue gas desulfurization (FGD) (also known as scrubbers) and selective catalytic reduction (SCR) are used by power plants to reduce pollutants such as SO2 and NOX. While many large coal-fired power plants have retrofitted with these technologies over the past few decades, uncontrolled power plants remain in operation.
Fleet Turnover
According to data from the Energy Information Administration (EIA), between 1990 and 2022, coal generation fell from 54.6% of the U.S. electricity mix to 19.7% as many older plants chose to retire. A significant amount of natural gas generating capacity was built in the 2000s, particularly lower-emitting natural gas combined cycle (NGCC) plants. As a result, natural gas generation increased from 12.3% to 39.8% of the U.S. electricity mix during that same time. The trend of higher-emitting coal-fired power plants being replaced by lower-emitting natural gas-fired power plants has delivered substantial emission reductions from the electric power sector. Additionally, renewable energy production is currently the fastest growing energy source in the U.S., with solar and wind dominating new power plant construction. To learn more about the electricity mix in the U.S., visit the eGRID website.
Over the past two decades, the cost of renewable energy technology has decreased significantly, making it competitive with existing coal and gas generation. By 2021, the average cost of wind declined by 70% while the cost of utility scale solar declined by 80% since 2010. Wind generation tripled between 2010 and 2021 and solar capacity has grown from less than 1 gigawatt (GW) in 2008 to over 73 GW in 2022.
The following charts are interactive. Click a state to see how the CO2 intensity and electricity mix have changed between 2000 and 2022 in the chart below the map. Click the reset button to return to the nationwide change in electricity mix.
Changes in Utilization of Existing Generation
Coal and natural gas have been the largest energy sources for the electric power sector over the past three decades. Natural gas power plants, particularly natural gas combined cycle (NGCC), generally have a significantly lower emissions profile per MWh of electricity generated. As natural gas prices have shifted down over the past decade, not only were new NGCC power plants built, but the existing power plants began to operate more, displacing some of the higher emitting coal generation.
The chart shows the increasing generation at NGCC plants and decreasing generation at coal-fired plants over time, as measured by capacity factor. The capacity factor of a power plant is the amount of actual power generated compared to its maximum output.
Reduced Growth in Demand for Electricity
While the existing fleet of power generating sources has become lower-emitting on average, the overall growth in demand for electricity has also slowed over the past decade. Initiatives such as EPA’s Energy Star Program and other demand-side energy efficiency measures at the federal and local levels have helped reduce electricity demand growth.
Looking Ahead
In 2021, Congress passed the Infrastructure and Jobs Act which included provisions and funding targeting significant changes in the electric power sector. This included substantial investment in grid infrastructure, including new transmission lines, incentives to preserve nuclear generation, and investments in technologies like advanced nuclear reactors, clean hydrogen, and carbon capture.
In 2022, Congress passed the Inflation Reduction Act to extend and expand tax credits for renewable and net zero emitting energy sources, and provide extensive grants and funding opportunities for beneficial electrification.
These laws are expected to produce or elevate a suite of advanced emissions mitigation technologies such as:
- Hydrogen power
- Carbon capture and storage including direct air capture
- Battery storage
- Electric vehicles
- Demand-side technologies such as energy efficiency, distributed renewable energy, and managed electric vehicle charging.
Learn about how power plants emissions impact human health and the environment ▶