The grilled opening into a room by which the amount of warm air from a furnace can be directed or controlled; may include a damper.

The process of producing electricity by transforming other forms or sources of energy into electrical energy; measured in kilowatt-hours.

Alternating current is carried by conductors and a ground to residential, commercial, or industrial consumers. The waveform of the phase power appears as a single continuous sine wave at the system frequency whose amplitude is the rated voltage of the pow ...

A device that captures the heat from the exhaust air from a building and transfers it to the supply/fresh fresh air entering the building to preheat the air and increase overall heating efficiency.

The amount of heat produced from the complete combustion of a unit of fuel. The higher (or gross) heating value is that when all products of combustion are cooled to the pre-combustion temperature, water vapor formed during combustion is condensed, and ne ...

An elementary particle of an atom with a negative electrical charge and a mass of 1/1837 of a proton; electrons surround the positively charged nucleus of an atom and determine the chemical properties of an atom.

A hydrocarbon gas obtained from underground sources, often in association with petroleum and coal deposits. It generally contains a high percentage of methane, varying amounts of ethane, and inert gases; used as a heating fuel.

A device that produces mechanical energy directly from two heat reservoirs of different temperatures. A machine that converts thermal energy to mechanical energy, such as a steam engine or turbine.

A corporation, person, agency, authority or other legal entity that owns and/or operates facilities for the generation, transmission, distribution or sale of electricity primarily for use by the public.

The space within a building or structure that is normally occupied by people, and that may be conditioned (heated, cooled and/or ventilated).

A type of water heater that circulates water through a heat exchanger in a boiler. The heated water then flows into an insulated storage tank.

A company or individual that is not directly regulated as a utility. These entities produce power for their own use and/or sell it to regulated utilities.

A configuration of an electrical circuit in which the voltage is the same across the terminals. The positive reference direction for each resistor current is down through the resistor with the same voltage across each resistor.

A heating system that uses only outside air for combustion and vents combustion gases directly to the outdoors. These systems are less likely to backdraft and to negatively affect indoor air quality.

A unit or measure of solar radiation; 1 calorie per square meter or 3.69 Btu per square foot.

An instrument for measuring solar radiation.

A heat exchanger for recovering heat from flue gases for heating water or air.

The transmission of electricity through power lines.

All the components of the appliance used to condition interior air of a building.

The change in direction of a ray of light when it passes through one media to another with differing optical densities.