Where Does Electricity Come From?

Power plants make electricity out of other forms of energy. Most electricity in the U.S. today comes from converting the heat energy released from burning fossil fuels--coal, natural gas and oil. The rest is generated from nuclear reactors and from renewable sources, such as sunlight, wind, falling water and geothermal heat (see Renewables, Unit 5).

In a typical power plant, a primary energy source like coal is burned to create heat, which is converted in a boiler to mechanical energy in the form of superheated, high-pressure steam. The steam is directed into a turbine, where it pushes on blades attached to a central shaft or rotor. The rapidly spinning rotor powers a generator.