The cost of producing one additional unit of a product.

Fuels that cannot be easily made or "renewed," such as oil, natural gas, and coal.

A sinusoidal quantity having a frequency that is an integral multiple of the frequency of a periodic quantity to which it is related.

A device used to transfer heat from a fluid (liquid or gas) to another fluid where the two fluids are physically separated.

A term applied to warm-air heating systems that deliver heated air to rooms by means of registers or baseboards located along exterior walls.

A machine for converting mechanical energy into electrical energy by magneto-electric induction; may be used as a motor.

The angle at which a solar collector or module is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection.

A unit of electricity consumption of one Watt over the period of one hour.

A popular term used to describe the increase in average global temperatures due to the greenhouse effect.

The average power output of a wind energy conversion system at a given mean wind speed based on a Raleigh frequency distribution.

As a component of a heating or cooling appliance, rows of tubing or pipe with fins attached through which a heat transfer fluid is circulated and to deliver heat or cooling energy to a building.

A measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature. When the air is fully saturated, its relative humidity is 100 percent.

A device for measuring power consumption.

The maximum energy demand or load in a specified time period.

A device that can be set to automatically turn appliances (lights) off and on at set times.

Energy available from the movement of the wind across a landscape caused by the heating of the atmosphere, earth, and oceans by the sun.

A structure or media from which heat can be absorbed or extracted.

The amount of kinetic energy gained by an electron when accelerated through an electric potential difference of 1 Volt; equivalent to 1.603 x 10

An electrical device for converting alternating current to direct current. The chamber in a cooling device where water is separated from the working fluid (for example ammonia).

The loss of heat as the water circulates through a water heater tank and inlet and outlet pipes.