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.

Of the energy supplied to electric power plants, 12% is distributed as electricity to residential, commercial, industrial, and transportation sectors; 22% is exported; and 66% is unused, largely lost as heat in the conversion of fuel to electricity.

Residential use accounted for 19% of regional end-use energy consumption and 27% of greenhouse gas emissions in 2011.

Commercial and institutional spaces accounted for 12% of regional end-use energy consumption and 14% of greenhouse gas emissions in 2011. Most of that energy was used for heating, cooling, and lighting.

Industry accounted for 29% of regional end-use energy consumption and 23% of greenhouse gas emissions in 2011. Most of that went to energy-intensive industries: coke, cement, glass, chemicals, paper, and metals.

Moving the region’s people and goods from one place to another was responsible for 39% of regional end-use energy consumption and 36% of greenhouse gas emissions in 2011.

While it’s impossible to avoid losing some energy as heat when converting energy from one form to another, opportunities abound for capturing heat for productive uses, better utilizing renewable sources, replacing combustion engines with electric motors, and improving efficiencies.

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 regionally in one year is measured in trillion (1 thousand billion) British Thermal Units (Btu). One trillion Btu is approximately the amount of energy used by 10,000 homes in one year.

In this region, solar photovoltaic power production is currently employed on a small number of individual homes and commercial and industrial buildings, but no utility-owned solar electric power installations were operating as of 2011.

One nuclear power plant provides 11% of the electricity generated in the region. Though it produces electricity locally, its primary fuel—uranium— is imported exclusively from outside the region. Thus the flow diagram shows nuclear power as a net energy import for the region.

Hydropower is renewable, free of CO₂ emissions, and more reliable than solar or wind energy, except during periods of prolonged drought. Damming rivers and streams is disruptive to local ecosystems and the existing resource base is limited, but future projects may harness energy from waves and currents.

Wind energy in the region and nationally has grown considerably in recent years and has a large potential for further expansion. But as an intermittent source, it still awaits an effective way to store its energy output.

Regionally, a small number of homes and commercial buildings employ geothermal heat pumps to leverage the relatively constant temperature and substantial mass of the earth’s soil, bedrock, and groundwater as a heat source or heat sink for direct heating and cooling.

More than two-thirds of the region’s homes rely on natural gas for heating and powering appliances. Until recently, natural gas was a small contributor to regional electric power production, but it is rapidly increasing its share. In 2011, the region exported 56% of the natural gas it produced.

Coal dominates the region’s energy flow, representing more than half its total energy supply, the greatest contributor to electric power production, and the largest energy export. It is relatively inexpensive for its energy content, but coal is also a major source of CO₂ emissions and pollutants that impact human health and the environment.

Biomass—which includes organic material such as wood, methane from landfills, and agricultural crops—is burned to generate electricity or provide direct heat. Biomass is also used to make biofuels (such as ethanol and biodiesel), which are often mixed with petroleum-based transportation fuels.

Oil is the predominant fuel source in the transportation sector—gasoline, diesel, and jet fuel all come from crude oil. Industries use oil for space heating, process heating, and as a raw material for common products such as asphalt, plastics, and chemicals. Only a small amount of oil is produced within the region, so it must import 96% of the oil it consumes.