Renewable energy sources can be replenished.
More than 150 years ago, wood supplied nearly 90% of the nation's energy needs. As the use of coal, petroleum, and natural gas expanded, the United States became less reliant on wood as an energy source. Today, using renewable energy sources like wood to meet the nation's energy needs is becoming more popular.
In 2014, consumption of renewable energy sources in the United States totaled about 9.6 quadrillion British thermal units (Btu)—1 quadrillion is the number 1 followed by 15 zeros—or about 10% of total U.S. energy consumption. About 13% of U.S. electricity was generated from renewable energy sources in 2014.
More than half of U.S. renewable energy use is for producing electricity. Biomass (wood and waste) is the second most commonly used renewable energy source. Biomass is used to produce heat and steam for industrial purposes, and it is also used for space heating. Biomass also includes biofuels like ethanol and biodiesel, which are used for transportation.
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 production and use of biofuels and nonhydroelectric renewable energy sources doubled from 2000 to 2014, mainly because of state and federal government mandates and incentives for renewable energy. The use of renewable fuels is expected to continue to grow over the next 25 years. The U.S. Energy Information Administration (EIA) projects that the United States will use nonrenewable fuels to meet most of its energy needs through 2040.
Why don't we use more renewable energy?
In the past, renewable energy has generally been more expensive to produce and use than energy produced using fossil fuels. Renewable resources are often located in remote areas, and it can be expensive to build power lines to the cities where the electricity produced from renewable energy is needed. The use of renewable sources is also limited by the fact that they are not always available—cloudy days reduce electricity generated from solar installations; days without wind reduce electricity from wind farms; and droughts reduce the water available for hydropower.
How do we measure renewable energy?
Each energy source is measured, purchased, and sold in different forms. Many units of measurement are used to measure energy. Learn more about converting energy units in the Energy units and calculators Energy Explained section.