U.S. power plants used renewable energy sources — water (hydroelectric), wood, wind, organic waste, geothermal, and sun — to generate about 13% of our electricity in 2011.
Most Renewable-Generated Electricity is from Hydropower
Renewable energy sources provided about 13% of total U.S. utility-scale electricity generation in 2011. The largest share of the renewable-generated electricity came from hydroelectric power (63%), followed by: wind (23%), biomass wood (7%), biomass waste (4%), geothermal (3%), and solar (<1%).
Electricity generation from renewable resources is primarily a function of generation capacity and the availability of the resource. The history of electricity generation has been different for each renewable source.
- Nearly all of the hydroelectric capacity was built before the mid-1970s, and much of it is at dams operated by federal government agencies.
- Biomass waste is mostly municipal solid waste which is burned as fuel to run power plants.
- Most of the electricity from wood biomass is generated at lumber and paper mills. These mills use their own wood waste to provide much of their own steam and electricity needs.
- The amount of installed wind generation dramatically increased in the past decade, due in part to Federal financial incentives and State government mandates, especially renewable portfolio standards.
- Unlike other renewable sources, a significant amount of solar power is generated by small-scale, customer-sited installations like rooftop solar (or, distributed generation). According to the Annual Energy Outlook 2012, these small solar facilities are projected to generate an estimated 6.74 billion kilowatthours of electricity in 2012.
- The contribution of renewable sources to electricity generation has evolved differently for each state.
The Availability of Renewable Resources Can Vary
Hydroelectric generation increases in some years and decreases in others, primarily due to variation in the amounts of rainfall and melting snowfall occurring in watersheds where major hydroelectric dams are located. The availability of biomass (wood and waste) and geothermal energy is generally consistent over the short term as is the generation from these resources. The availability of wind and solar energy has daily and seasonal patterns, so resulting generation fluctuates widely.
The United States Is Second in Renewable Electricity Generation
China leads the world in total electricity generation from renewable energy due to its recent massive additions to hydroelectric capacity, followed closely by the United States, Brazil, and Canada. However, the United States produces the most electricity from non-hydroelectric renewable sources; about 70% more than Germany, the next largest producer of non-hydro renewable electricity.
Why We Don’t Use More Renewable Energy
Although most renewable energy power plants have less environmental impact than fossil and nuclear power plants, there are two main reasons why we don’t use more renewable energy.
- Renewable Energy Technologies Are Often Expensive: Renewable energy power plants can be more expensive to build and to operate (in terms of dollars per unit of electricity output) than natural gas or even coal plants.
- Renewable Resources Are Often Geographically Remote: Many renewable resources are available only in remote areas, and building transmission lines to deliver power to large metropolitan areas is expensive.
Policies Aim to Increase the Use of Renewable Energy
Three kinds of policies to increase the use of renewable energy are:
- Tax credits: The Renewable Electricity Production Tax Credit, a federal incentive, has encouraged a major increase in generation from wind and other eligible renewable sources.
- Targets: Many states have Renewable Portfolio Standards (RPS), which require electricity providers to generate or acquire a certain portion of their power supplies from renewable sources. However, many RPS programs have "escape clauses" if renewable generation exceeds a cost threshold.
- Markets: A number of states have built Renewable Energy Certificates/Credits (RECs) into their Renewable Portfolio Standards. This allows electricity providers to sell renewable energy certificates/credits. Some states have made REC markets mandatory, requiring electricity providers to produce or acquire renewable generation to reduce reliance on fossil fuels to generate electricity. (Detailed information on federal and state renewable energy policies are available from the Database of State Incentives for Renewables & Efficiency.)
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