Imported electricity accounts for more than 30% of California’s total electricity supply. It comes from various sources, including coal, natural gas, nuclear power, hydropower, and other renewables.

Electricity is called secondary energy because it’s generated from a mix of primary energy sources, mainly natural gas in California. About 22% of the total California energy supply goes to producing electricity.

Residential use accounted for about 13% of total California energy consumption in 2013, primarily from electricity and natural gas. The top energy uses were space heating and water heating.

Commercial buildings including colleges, hospitals, hotels, retail, and offices accounted for 10% of theenergy used in California in 2013. Most of that energy was used for lighting and space heating.

Industry accounted for 21% of the energy used by California in 2013, primarily from natural gas and oil. The most energy-intensive industries in California are the oil industry and manufacturing.

Cars, trucks, buses, trains, ships, and planes compose the transportation sector, which is powered mostly by oil. California uses 40% of its total energy each year to move people and goods from one place to another.

There are many opportunities to improve California’s energy efficiency, but it’s impossible to avoid losing some energy as heat when converting energy from one form to another. The principles of physics place upper limits on how efficient a heat engine, power plant, or oil refinery can be.

Useful energy describes the amount of energy that went toward accomplishing the work that needed to be done, whether it was moving a car, lighting a bulb, or driving a turbine to generate power, as well as direct heat for space heating, cooking, manufacturing, etc.

The enormous quantity of energy consumed in California in one year is measured in Trillion (1 million million) British Thermal Units. California accounts for about 7% of the United States’ total energy consumption.

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California's deserts have considerable solar energy potential. California is the first state to get more than 5% of its utility-scale electricity generation from its solar resource. On a smaller scale, the California Solar Initiative offers cash back to consumers who install solar power systems on rooftops of homes and businesses.

California has only one operating nuclear power plant: Diablo Canyon, near San Luis Obispo. Nuclear plants don’t emit greenhouse gases or pollutants that are harmful to human health and the environment, but they do create radioactive waste that must be stored safely.

California has 287 hydroelectric plants, mostly in the eastern mountain ranges. Hydropower has averaged almost one-sixth of the state's net electricity generation in the past decade— its share varies with annual precipitation. With adequate snowpack, hydroelectric power can account for more than one-fourth of California's net electricity generation, but in 2013 it supplied less than 12%.

More than 13,000 wind turbines— 95 percent of all of California's wind generating capacity and output— are located in three primary regions: Altamont Pass (east of San Francisco), Tehachapi (southeast of Bakersfield), and San Gorgonio (near Palm Springs, east of Los Angeles). Wind provides 7.5% of California’s electricity generation.

The heat from Earth’s molten interior, which is often associated with volcanic or seismically active regions, provides geothermal energy. California, with its location on the Pacific "Ring of Fire," has 25 Known Geothermal Resource Areas, 14 of which have temperatures of 300 degrees Fahrenheit or greater. Geothermal provides about 7% of California’s electricity generation.

More than one-third of the energy consumed in California is from natural gas. Since California itself only produces about 10% of the natural gas it consumes, most of it must be imported.

California has been phasing out coal-fired power plants for electricity generation in an effort to reduce climate-changing impacts of fossil fuels. Other than the small amount currently consumed by the electric power sector, coal is still used in some industrial facilities.

California leads the nation in utility-scale electricity generation from biomass. Industrial and residential sectors also use biomass, mainly as a heat source. Nearly half of California’s biomass is converted into biofuels (such as ethanol and biodiesel) for use in the transportation sector.

Petroleum is the predominant fuel source in the transportation sector—gasoline, diesel, and jet fuel all come from crude oil. California ranks third in the nation in petroleum refining capacity and accounts for more than one-tenth of the total U.S. capacity.