# The most popular renewable energy sources [ PDF ]

A renewable energy source means energy that is sustainable - something that can't run out, or is endless, like the sun. When you hear the term 'alternative energy' it's usually referring to renewable energy sources too. it means sources of energy that are alternative to the most commonly used non-sustainable sources like coal.

The most popular renewable energy sources currently are:
• Solar energy
• Wind energy
• Hydro energy
• Tidal energy
• Geothermal energy
• Biomass energy