Renewable energy utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. Renewable energy technologies range from solar power, wind power, and hydroelectricity to biomass and biofuels for transportation. Approximately 13 percent of primary energy comes from renewable energy sources, with most of this coming from traditional biomass like wood-burning. Hydropower is the next largest source, providing 2-3%, and modern technologies like geothermal, wind, solar, and marine energy together produce less than 1% of total world energy demand. The technical potential for their use is very large, exceeding all other readily available sources.

Renewable energy technologies are sometimes criticized for being unreliable or unsightly, yet the market is growing for many forms of renewable energy. Wind power has a worldwide installed capacity of 74,223 megawatts (MW) and is widely used in several European countries and the USA. The manufacturing output of the photovoltaic (PV) industry reached more than 2,000 MW per year in 2006, and PV power plants are particularly popular in Germany. Solar thermal power stations operate in the USA and Spain, and the largest of these is the 354 MW SEGS power plant in the Mojave Desert.  The world's largest geothermal power installation is The Geysers in California, with a rated capacity of 750 MW.  Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18 percent of the country's automotive fuel.  Ethanol fuel is also widely available in the USA.

While there are many large-scale renewable energy projects, renewable technologies are also suited to small off-grid applications, sometimes in rural and remote areas, where energy is often crucial to human development.  Kenya has the world's highest household solar ownership rate with roughly 30,000 small (20-100 watt) solar power systems sold per year.

Climate change concerns coupled with high oil prices and increasing government support are driving increasing renewable energy legislation, incentives and commercialization. EU leaders reached agreement in principle in March that 20 percent of the bloc's energy should be produced from renewable energy fuels by 2020, as part of its drive to cut emissions of carbon dioxide, blamed in part for global warming.  Investment capital flowing into renewable energy reached a record $74 billion in 2007.  Some very large corporations such as BP, GE, Sharp, and Shell are investing in the renewable energy sector.