Renewable electric generation is a broad category fueled by sources that can be naturally replenished. There are many types of renewable fuels and technologies used (see individual links for a more detailed description of each type):
- Biofuel — Organic non-fossil fuel burned directly to create steam for a steam turbine, or biogas used in a gas turbine
- Geothermal — Hot water or steam extracted from underground reservoirs in the earth's crust that is used to drive steam turbines
- Hydro — Moving water from impoundment (such a reservoir) or diversion that drives a water turbine
- Hydrokinetic – Electricity derived from the movement of water including waves, currents, and tides
- Municipal Solid Waste (MSW) — Garbage incinerated in a furnace or fluidized bed combustor to create heat and then steam to drive a steam turbine
- Solar — Sunlight applied to a photovoltaic cell or sunlight used to heat liquids to create steam that is then used in a steam turbine
- Wind — Electric generator whose shaft is driven by the force of moving air
Wind and utility-scale solar PV projects are often cost-competitive with other generation alternatives on a 10-year overall cost basis. But O&M costs vary greatly by technology. The two big advantages of renewable power are that many technologies have no ongoing fuel cost (wind, solar) and environmental impacts are generally minimal. One drawback is that many renewable sources are variable and not always available. Thus, system operators must plan for other flexible resources when including renewables in the generation mix.
Development of renewable generation — especially wind and solar power — has accelerated in recent years. Factors fostering this development include rapidly falling costs for wind and solar photovoltaic projects, concerns over future gas prices, concerns over environmental impacts of fossil fuel generation, renewable portfolio mandates in some states, green power programs offered by some utilities and retail marketers (which allow consumers the choice to be served by green power), and large corporate energy users choosing to invest in renewable power.