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What's a watt?

What's a watt? A primer

March 1, 2001


Douglas Clement Senior Writer

1 watt is a small amount of power; technically, one joule per second. It takes approximately 746 watts to equal 1 horsepower.

1 kilowatt = 1 thousand watts
1 megawatt = 1 million watts (or 1 thousand kilowatts)
1 gigawatt = 1 billion watts (or 1 thousand megawatts)

A kilowatt-hour is a kilowatt of electricity supplied to a circuit for one hour.

A 100-watt bulb burning for 10 hours requires 1 kilowatt-hour of electricity. In 1998, the average U.S. price for 1 kilowatt-hour of electricity was 6.74 cents.

A typical American household uses 857 kilowatt-hours of electricity each month, or about 10 megawatt-hours a year.

The United States had 776 gigawatts of generating capability in 1998 and during the course of the year, those generators produced 3.6 billion megawatt-hours of electricity. Ninth District states (including all of Wisconsin, but excluding Michigan) had 35.6 gigawatts of capability and produced 172 million megawatt-hours of power.

The largest electricity generator in the United States is the Grand Coulee Dam in Washington, with a net capability of 7.1 gigawatts (7,100 megawatts). In the Ninth District, the largest generator is Minnesota's Sherburne coal plant with a capability of 2.3 gigawatts.

A typical nuclear power plant built in 1980 generates 1.1 gigawatts (1,100 megawatts) of electricity. An average 1985-era coal plant generates 600 megawatts. Modern combined-cycle natural gas turbines are smaller, around 250 megawatts.

Micropower generators are far smaller, generally well under 10 megawatts (though some definitions extend the range as high as 50 megawatts). Microturbines can generate from 30 to 300 kilowatts; fuel cells range from 1 to 300 kilowatts. Hybrid fuel cell/turbines currently under development could be scaled between 400 kilowatts and 10 megawatts.

Sources: U.S. Energy Information Administration, EPRI, Edison Electric Institute and Worldwatch Institute


Douglas Clement
Senior Writer

Douglas Clement was a managing editor at the Minneapolis Fed, where he wrote about research conducted by economists and other scholars associated with the Minneapolis Fed and interviewed prominent economists.