Energy output from a system that equals energy input.

The amount of heat in a quantity of matter at a specific temperature and pressure.

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

The amount of heat introduced to a space from all heat producing sources, such as building occupants, lights, appliances, and from the environment, mainly solar energy.

The heat that flows from the building interior, through the building envelope to the outside environment.

A device that transfers heat by the continuous evaporation and condensation of an internal fluid.

An electricity powered device that extracts available heat from one area (the heat source) and transfers it to another (the heat sink) to either heat or cool an interior space or to extract heat energy from a fluid.

A water heater that uses electricity to move heat from one place to another instead of generating heat directly.

The ratio of fuel energy input as heat per unit of net work output; a measure of a power plant thermal efficiency, generally expressed as Btu per net kilowatt-hour.

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

A structure or media that absorbs heat.

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

A device or media that absorbs heat for storage for later use.

The amount of heat that a material can absorb and store.

The flow of heat from one area to another by conduction, convection, and/or radiation. Heat flows naturally from a warmer to a cooler material or space.

A gas or liquid used to move heat energy from one place to another; a refrigerant.

Any coefficient used to calculate heat transmission by conduction, convection, or radiation through materials or structures.

The quantity of heat necessary to raise the temperature of a specific mass of a substance by one degree.