At least 35% of all Planet tapped primary energy is converted into electricity. Among Developed Nations an average of 42% of all primary energy is converted into electricity. Coal is used to generate about 40% of Planet electricity and its use is expanding as Developing Nations increase their energy demands. Natural gas meets 20% of electric production, hydro 16%, nuclear 16% and oil 7%. Hydro provides about 16% of Planet electricity. Other renewables provide less than 2%. Power plants (except hydro) use combustion technology to heat liquids to boil and expand as steam to turn turbines which turn generators which generate electricity.