Changes

'''Alternative energy''' (also referred to as '''renewable energy''') refers to an energy source that is naturally replenished, such as wind, sunlight, rain, tides, and [[geothermal energy|geothermal]] heat.  The generation of [[electricity]] by means of alternative energy sources is generally more expensive than traditional, coal-powered generators.<ref>[http://portsmouthrienergy.com/A2.pdf Portsmouth Sustainable Energy Cost Analysis]</ref><ref>[http://www.nytimes.com/2009/03/29/business/energy-environment/29renew.html ''New York Times'' Online]: Cost Works Against Alternative Energy, March 2009.</ref>

'''Alternative energy''' refers to energy sources that do not come from fossil fuels.<ref>[http://www.mms.gov/offshore/RenewableEnergy/Definitions.htm U.S. Department of the Interior Offshore Energy and Minerals Management - Renewable Energy Program Definitions]</ref> This term is often used interchangeably with '''renewable energy''', which refers to an energy source that is naturally replenished, such as wind, sunlight, rain, tides, and [[geothermal energy|geothermal]] heat.  The generation of [[electricity]] by means of alternative energy sources is usually more expensive than traditional, [[coal]]-powered generators.<ref>[http://portsmouthrienergy.com/A2.pdf Portsmouth Sustainable Energy Cost Analysis]</ref><ref>[http://www.nytimes.com/2009/03/29/business/energy-environment/29renew.html ''New York Times'' Online]: Cost Works Against Alternative Energy, March 2009.</ref> However, because renewable energy has no fuel costs and often requires less maintenance than fossil fuel generators, renewable energy is usually less expensive than fossil fuel-derived energy once initial capital costs are covered.<ref>http://www.ren21.net/pdf/RE_GSR_2009_update.pdf</ref> Renewable energy generators and power plants usually emits little-to-no pollution while operating, though they can cause other environmental effects, such as effects on neighboring ecosystems.<ref>[http://www.ucsusa.org/clean_energy/technology_and_impacts/impacts/environmental-impacts-of.html Environmental Impacts of Renewable Energy Technologies]</ref>

There is debate whether to classify hydroelectric dams as renewable.

There is debate whether to classify hydroelectric dams as renewable.