Some types of generators use falling water or wind to turn the turbines. Other generators use steam. Steam is made by heating water. The heat comes from burning fuels, such as coal or oil, or from a nuclear reaction.

In a nuclear reaction, atoms of material such as uranium are split. This causes the atoms to release a lot of heat.

It costs money to generate electricity. How much it costs depends on where the materials needed to generate electricity are located. The cost can also depend on how much work and time it takes to generate electricity.