Which Renewable Resource Produces The Most Electricity In The United States?

As climate change becomes an increasing threat and fossil fuels continue to be depleted, there is a rising global demand for renewable energy sources. In the United States, renewable electricity generation has doubled over the past decade, now accounting for 20% of utility-scale electricity generation. With ambitious renewable energy targets set for 2030 and beyond, it’s important to examine the current breakdown of renewable electricity sources in the U.S.

The main renewable energy technologies used for utility-scale electricity generation in the U.S. are hydroelectric power, wind power, solar power, geothermal power, and biomass power. Each has advantages and disadvantages in terms of cost, reliability, environmental impact, and scalability. This article will provide an in-depth comparison of which renewable resource currently produces the most electricity in the United States.

Hydroelectric Power

Hydroelectric power is generated by using dams on rivers to control water flow. As water in a reservoir builds up behind the dam, it flows through turbines and generators to produce electricity [1]. The force of moving water spins the turbines, which then spin magnets inside copper wire coils to generate an electric current. The larger the dam and water flow, the more electricity that can be generated. According to the U.S. Energy Information Administration, hydroelectric power accounted for 28.7% of total U.S. renewable electricity generation and 6.2% of total electricity generation in 2021

The scale of hydroelectric power in the United States is immense. The country has over 2,300 hydroelectric power plants, which together have a capacity of 80 gigawatts [2]. Some of the largest hydroelectric dams are on the Columbia River, including the Grand Coulee Dam in Washington state which is the largest power plant in the U.S. with over 6,000 megawatts of capacity [3]. While dams provide clean renewable energy, there are environmental concerns around habitat destruction and changes to ecosystems.

Wind Power

Wind turbines convert the kinetic energy in wind into mechanical power through rotating blades connected to a generator. As the blades spin, they turn an internal shaft connected to a gearbox that increases the rotations per minute to the level needed by the generator to produce electricity. The generator converts the mechanical rotation into electrical energy. Most wind turbines have a horizontal axis arrangement with two or three propeller-like blades facing into the wind.

Wind power capacity in the United States has expanded rapidly in recent years. According to the U.S. Department of Energy, wind power accounted for over 22% of new electricity generation capacity added in the country in 2022, second only to solar power (source). Total installed wind capacity grew from about 25 GW in 2000 to over 134 GW by the end of 2021. The DOE projects wind capacity to reach over 404 GW by 2050.

However, wind power output can vary based on wind conditions and is considered an intermittent renewable resource. Production is highest in windy months and may drop during low wind periods, requiring backup from other sources when electricity demand is high. The intermittent nature of wind can present grid integration and transmission challenges.

Solar Power

Solar photovoltaic (PV) panels convert sunlight directly into electricity using semiconducting materials that exhibit the photovoltaic effect. When sunlight hits the panels, electrons are knocked loose from the atoms in the semiconducting material, causing electricity to flow. The PV cells are wired together to form panels and arrays that can be mounted on rooftops or ground-mounted to generate electricity on both residential and utility scales.

The cost of solar PV panels has dropped dramatically over the last decade, leading to rapid growth in solar power capacity in the United States. According to the U.S. Energy Information Administration, utility-scale solar capacity grew from 2.5 gigawatts in 2010 to over 60 gigawatts by the end of 2019^[1]. Falling costs have made solar power competitive with fossil fuels in many parts of the country.

However, the intermittent nature of solar power creates challenges. Solar energy is only generated when the sun is shining, so storage systems or backup power are needed for times when sunlight is reduced, such as nighttime and cloudy days. Researchers are working on improving energy storage technology to overcome these limitations.

Geothermal Power

Geothermal energy harnesses heat below the earth’s surface to generate electricity. Hot water or steam trapped in fractured or porous rock is accessed by drilling and pumped to the surface to drive turbines that activate a generator. According to the U.S. Energy Information Administration, utility-scale geothermal power plants in the United States have an electricity generation capacity of at least 1 megawatt. https://www.eia.gov/energyexplained/geothermal/use-of-geothermal-energy.php

As of 2019, the installed geothermal electricity generation capacity in the U.S. was approximately 3,676 megawatts, with the U.S. leading global geothermal capacity at around 25%. However, geographical limitations restrict widespread adoption, as geothermal reservoirs require particular subsurface conditions only present in certain locations, such as western states like California and Nevada. https://en.wikipedia.org/wiki/Geothermal_energy_in_the_United_States

Biomass Power

Biomass refers to organic matter that comes from plants and animals and can be used as an energy source. Biomass contains stored energy from the sun. Plants absorb sunlight and use photosynthesis to convert it into chemical energy. When biomass is burned, the chemical energy is released as heat that can generate electricity with a steam turbine. Some common biomass fuels are wood, agricultural waste, and ethanol.

In 2021, biomass accounted for about 5% of total U.S. primary energy consumption, providing about 4.9 quadrillion BTU. The main biomass feedstocks for power generation are forestry and agriculture residues, organic waste from municipal and industrial sources, crops grown specifically for energy production, and methane from landfills. Currently, biomass provides about 1.5% of U.S. electricity generation.

While biomass can provide clean energy, some limitations exist. There are restricted supplies of biomass, and it may compete with food crops for land use. Burning biomass also produces air pollution in the form of soot, ash, carbon monoxide, nitrogen oxides, and volatile organic compounds. Overall, biomass represents a renewable fuel source that avoids fossil fuels and diverts waste, but its scale is constrained by restricted supplies.

Comparing Renewable Sources

When looking at renewable energy sources in the United States, some clear trends emerge. Hydroelectric power has historically been the largest renewable electricity source. However, wind and solar power capacity have grown rapidly in recent years. According to the U.S. Energy Information Administration, in 2021 hydroelectric power accounted for 30% of total U.S. renewable electricity generation, wind power accounted for 26%, and solar power accounted for 13% (EIA).

Overall renewable energy accounts for about 20% of U.S. electricity generation as of 2021. This represents substantial growth, as the renewable share was only 9% in 2008. Going forward, wind and solar are expected to continue their growth trajectories. The U.S. Department of Energy projects wind power capacity to more than double and solar capacity to quadruple between 2020 and 2050 (DOE). Since 2000, U.S. wind power generation has increased over 90-fold while solar has grown over 4,000-fold.

So while hydropower has historically led, other sources like wind and solar are seeing rapid gains. The energy mix is diversifying and renewables as a whole are claiming a steadily increasing share of total U.S. electricity generation.

Challenges for Renewables

While renewable energy sources like wind, solar, and hydropower offer many benefits, they also face some unique challenges compared to conventional power plants. One major challenge is intermittency and reliability. Wind and solar power depend on weather conditions and time of day, which makes their electricity generation variable and unpredictable. This complicates grid operations and matching supply with demand (Source).

Large scale storage and transmission capabilities are needed to store excess renewable electricity when supply exceeds demand and transport it to areas of need. However, these technologies are still developing and can be costly to implement at scale (Source).

Finally, most renewables currently have higher costs per kilowatt hour compared to conventional power from fossil fuels and nuclear energy. The capital costs of building wind farms, solar arrays, and dams are often higher than traditional power plants. However, costs are falling as technology improves and deployment expands.

Future Outlook

The future continues to look bright for renewable energy growth in the United States. According to the Renewable Electricity Futures Study by the National Renewable Energy Laboratory, renewables have the potential to supply 80% of total U.S. electricity generation by 2050 with continued advances in renewable technologies and sustained policy support.

For renewables to realize their full potential, continued policy support will be critical at both the federal and state levels. Tax incentives, renewable portfolio standards, and streamlined permitting processes for new projects will help drive further investment and deployment. Stakeholder engagement and community education will also be key to gaining public acceptance.

Emerging technologies like offshore wind, advanced geothermal, and wave/tidal energy show tremendous promise in the coming decades. For example, offshore wind capacity is projected to reach 22 GW by 2030 and 86 GW by 2050. Continued research, development, and demonstration will enable these resources to achieve commercial viability and make greater contributions to the renewable energy mix over time.

With the right policies and sustained technology innovation, renewables appear well-positioned to transform the U.S. energy sector and deliver major environmental and economic benefits. However, continued commitment by policymakers, industry, researchers, and the public will be essential to realizing this clean energy future.

Conclusion

In reviewing the major sources of renewable electricity in the United States, it’s clear there are several options available that can generate substantial amounts of power. Hydroelectric dams have historically produced the most renewable electricity due to the nation’s extensive dam system and rivers. However, over the last decade, wind power has emerged as a fast growing renewable source and now generates more electricity than hydroelectric dams. Looking forward, solar also has huge potential for growth thanks to photovoltaic technology improvements and declining costs. While no single renewable source currently generates the majority of US electricity needs, the combined contributions of hydroelectric, wind, solar, geothermal and biomass sources are increasing rapidly. With further investments and supportive policies, renewables appear well positioned to provide an ever greater share of the nation’s electricity. This transition promises to deliver economic, environmental and energy independence benefits.