Renewable energy is generated by sources that can be replenished within a relatively short period of time. Solar, wind, water, biomass, and geothermal are all renewable energy sources.¹ Green energy, while similar to renewable energy, is a subset of sources that have the highest environmental benefits.² Clean energy sources emit low carbon, and include renewable energy sources along with nuclear power.³

Renewable energy sources have been used to generate heat and power for much of human history, and more relatively recently, electricity. Renewable energy makes up 12% of primary energy use in the United States and 11% worldwide.⁴ While there is still a strong dependence on fossil fuels for heating, electricity and transportation, the oil crises of the 1970s pushed for stronger investment into alternative energy sources. Additionally, the negative effects of climate change have increased public demand in finding non-fossil fuel based energy, aided by government incentives and standards.⁵

This guide focuses on resources relevant to researching the business of generating and distributing renewable energy. To that end, there are sections of this guide about the power grid and the electric power sector which consumes energy in order to generate and sell electricity. This guide does not include technical or engineering information on developing renewable energy technologies. Information on the power grid, climate change, and energy policy are included as they relate to the renewable energy industry. For information on corporate responsibility, which includes businesses that use renewable or green energies, see Corporate Social Responsibility: A Resource Guide. Additional information on green businesses is in Green Business: Sources of Information. Most of the guide takes a U.S. perspective, but international sources are included throughout.

For an excellent overview U.S. energy sources, there have been a number of Congressional Research Service reports on renewable energy topics, including: