Renewable energy sources can be replenished.
More than 150 years ago, wood supplied nearly 90% of the nation's energy needs. As more consumers began using coal, petroleum, and natural gas, the United States relied less on wood as an energy source. Today, the use of renewable energy sources is increasing, especially biofuels, solar, and wind.
In 2015, about 10% of total U.S. energy consumption was from renewable energy sources (or about 9.7 quadrillion British thermal units (Btu)—1 quadrillion is the number 1 followed by 15 zeros). More than half of U.S. renewable energy is used for producing electricity, and about 13% of U.S. electricity generation was from renewable energy sources in 2015.
Renewable energy plays an important role in reducing greenhouse gas emissions. When renewable energy sources are used, the demand for fossil fuels is reduced. Unlike fossil fuels, non-biomass renewable sources of energy (hydropower, geothermal, wind, and solar) do not directly emit greenhouse gases.
The consumption of biofuels and nonhydroelectric renewable energy sources more than doubled from 2000 to 2015, mainly because of state and federal government mandates and incentives for renewable energy. The U.S. Energy Information Administration (EIA) projects that the use of renewable energy in the United States will continue to grow through 2040.
Why don't we use more renewable energy?
In general, renewable energy is more expensive to produce and to use than fossil fuel energy. Favorable renewable resources are often located in remote areas, and it can be expensive to build power lines from the renewable energy sources to the cities that need the electricity. In addition, renewable sources are not always available:
- Clouds reduce electricity from solar power plants.
- Days with low wind reduce electricity from wind farms.
- Droughts reduce the water available for hydropower.