California's Electricity Consumption and Production: Getting a Handle on the Numbers

Electricity consumption is measured in watts, the amount of energy converted per unit time. A typical household heater converts electrical energy to heat energy at a rate of 1,500 watts, or 1.5 kilowatts (kW). The total consumption of energy by the space heater over the course of an hour is (1.5 kW x 1 hour = 1.5 kilowatt-hours (kWh). On average California households use about 15 to 25kWh/day, or 450 to 750 kWh/month. More than half of residential electricity consumption is used for lighting and refrigeration.

California's total electricity consumption in 1999 was about 253,000 gigawatt-hours (one gigawatt-hour (GWh) is 1 million kWh). Residential consumption accounted for 30% of the total, followed by commercial (35%), industrial (21%), agricultural (7%) and other (6%) uses. In 2001, the Independent System Operator (ISO)-controlled areas of California consumed about 19,000 GWh/month on average. The peak demand for electricity at any one time is just as important as consumption. California's rotating outages in 2000 and 2001 were used to keep peak demand from exceeding the rate at which power plants could provide electricity. In 2001, the highest peak demand for electricity occurred in August and was about 41 GW (or 41,000 megawatts (MW)).

California's total electricity production in 1999 was about 276,000 Gwh. The production amount exceeds consumption because some electricity is used for transmission and distribution. About 31% of production was from natural gas and oil facilities, 15% each from hydroelectric and nuclear facilities, 13% from coal facilities, 8% from geothermal, waste, wind and solar facilities. The remaining 18% of California's electricity was imported from out of state.

California's power plants meet both consumption and peak demand needs through their generating capacity. Total in-state generating capacity in 1999 was about 53,000 MW. More than half of the state's electricity generating capacity is provided by natural gas (and some oil) plants. Hydroelectric capacity is also large (27%) but production is highly variable, depending on the water available. The largest electricity generating facilities are the state's two nuclear power plants, each with a capacity of about 2,100 MW. Average capacities of cogeneration natural gas plants and hydroelectric, coal, geothermal, waste, wind and solar plants range from 10 to 57 MW. The average capacity of non-cogeneration gas and oil plants is about 355 MW. Total (or overall) production depends on the number of hours a plant runs as well as its generating capacity, and often plants are taken off-line for maintenance or lack of the resource fuel.

Conversion factors: 1 gigawatt (GW) = 1 thousand megawatts (MW) = 1 million kilowatts (kW)

LWVC Board Update originally published June 7, 2002