Hydro plants use the force of falling or flowing water to generate electricity. High-head plants use dam structures to take advantage of the force of falling water, while run of the river plants use river flow to spin the turbines. This energy source is renewable, free and results in no hazardous emissions or solid waste. Unfortunately, hydro power plants, especially large-scale reservoirs and dams, can adversely impact the environment and water life by changing the water temperature and preventing free movement of fish. Also, the amount of electricity generated is dependent on the flow and the area’s precipitation and cannot respond to the demand.

Biomass energy, or biofuel, comes from natural material, such as wood products, municipal solid waste, agricultural crops and even landfill gases. A few examples of large-scale biomass energy production include capturing and burning methane gas from farms and landfills, growing switchgrass as an agricultural crop and burning it along with coal. Biomass contains no sulfur, and therefore does not contribute to acid rain. It reuses waste, thus diverting it from landfills and saving landfills space. And since any CO2 emitted during the process of electricity generation is reabsorbed by new plant material, no new carbon dioxide is added to the atmosphere. Growing agricultural crops for energy production also helps stabilize the soil, reduces erosion and chemical runoff, controls flooding and enhances wildlife habitat.

Geothermal technology uses the natural warmth of the earth to heat and cool buildings and produce electricity. A geo power plant taps into steam or hot water reservoirs underground and uses the heat to drive an electrical generator. It has a minimal impact on the environment because it emits no nitrogen oxides, very few sulfur dioxides, and 1,000 to 2,000 times less carbon dioxide than a fossil fuel plant. Geothermal is the most energy-efficient heating and cooling system on the market, and can lower heating and cooling bills significantly.

The simplest way to take advantage of solar power is to use daylight instead of lighting powered by electricity. Building a house with "daylighting" techniques, according to the U.S. Department of Energy, can save 40% to 60% in lighting costs. Photovoltaic technology uses semiconductor material to convert sunlight directly into electricity. This technology is non-polluting, silent, and involves little maintenance since there are no moving parts. Photovoltaic power can also be stored in deep-cycle batteries for evening or back-up use. PV power plants, located primarily in California, use massive lenses and reflectors to concentrate the sun's energy on a fluid-filled pipe. The heated fluid is used to drive a conventional electric generator.

Wind is a free, non-polluting, renewable energy resource that is harnessed by a wind turbine. Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. This process is quiet, non-interfering, and has no undesirable effect on the environment. Thanks to two decades of innovative technological developments, modern wind turbines are highly reliable and cost effective. The communities in which wind projects are located receive substantial economic and community development benefits.