Alternative energy refers to energy sources which are not based on the burning of fossil fuels or the splitting of atoms. Some definitions even include nuclear energy since this does not have the harmful effect of carbon emissions.

The renewed interest in this field of study comes from the undesirable effects of pollution both from burning fossil fuels and from nuclear waste by-products. Alternatives include: wind power, solar power, geothermal, tides and hydroelectric and biomass.

The term alternative energy is being used more and more interchangeably with renewable energy.