Global warming: Similar to global climate change, but refers more specifically to temperature, whereas global climate change encompasses the broader changes associated with elevated greenhouse gas levels, such as dryer deserts, increased numbers of hurricanes and warmer oceans.

Graywater or greywater: Waste water from a household source other than a toilet. This water can be used for landscape irrigation, depending upon the source.

Green building: A building constructed or renovated to incorporate design techniques, technologies and materials that minimize its overall environmental impacts.

Greenhouse effect: The heating effect due to the trapping of radiation from greenhouse gases produced from natural and human sources.

Greenhouse gases: While gases like carbon dioxide, methane, nitrous oxide, ozone and water vapor naturally occur in the earth’s atmosphere, human activities -- most notably the burning of fossil fuels to produce heat and electricity -- can artificially increase concentrations. They're called greenhouse gases because they remain in the atmosphere and intensify the sun’s heat, just like the glass walls of a greenhouse. Greenhouse gases are the primary source of global climate change.

Green power: A popular term for energy produced from clean, renewable energy resources.

Greenwash: Misinformation disseminated by a company or organization so as to present an environmentally responsible public image.

Hybrid system: A renewable energy system that includes two different types of technologies that produce the same type of energy.

Hydroelectric power: Electricity produced by the force of water falling through a hydroturbine that spins a generator.

Incandescent: Lighting that uses an electrically-heated filament to produce light in a vacuum or inert gas-filled bulb.

Insulation: Materials that prevent or slow down the movement of heat.

Insulation blanket: A pre-cut layer of insulation applied around a water heater storage tank to reduce heat loss from the tank.

Kilowatt (kW): A standard unit of electrical power equal to one thousand watts.

Kilowatt-hour (kwh): A unit or measure of electricity supply or consumption of 1,000 watts over the period of 1 hour.

Megawatt: One thousand kilowatts or 1 million watts.

Megawatt-hour: One thousand kilowatt-hours or 1 million watt-hours.