Energy Glossary

Here is a quick overview of terms used in this guide and that you’ll need to know as you gather information about your home heating and cooling options.

AIR SOURCE HEAT PUMP A heating-cooling unit that transfers heat in either direction between the air outside a home and the indoors.

AIR SUPPLY FOR COMBUSTION The air that a furnace, boiler or space heater requires to burn fuel.

AQUASTAT A thermostat that controls the water temperature in a boiler.

BOILER The heating unit used with a hot water (hydronic) distribution system.

CENTRAL AIR CONDITIONER A unit that cools an entire house by removing heat from the inside air and releasing it outside.

CONTROLS Devices such as a thermostat that regulate a heating or cooling system.

CONVENTIONAL GAS FURNACE OR BOILER A gas heating unit with an annual fuel utilization efficiency (AFUE) less than 70%. It exhausts through a masonry chimney (which should be lined) or metal “B” vent.

COST-EFFECTIVE HEATING/COOLING SYSTEM One that produces good value for money after all costs (purchase, installation, financing and energy charges) are considered.

DISTRIBUTION SYSTEM The components of a heating or cooling system that deliver warmed or cooled air, or warmed water, to the living space.

DOMESTIC HOT WATER Hot water used for household purposes.

EARTH ENERGY SYSTEM (ground source heat pump) A heat pump that transfers heat from the earth or ground water in cold weather and transfers it to the house through an underground piping system for space heating, cooling or water heating. The process reverses in warm weather, and heat is discharged to the ground or water.

ELECTRICAL RESISTANCE HEATING Heat produced by passing electricity through a resistor.

FLAME RETENTION HEAD BURNER A higher-efficiency burner in an oil furnace. It produces a hotter flame and operates with a lower air flow, thus reducing heat loss up the chimney.

FLUOROCARBON REFRIGERANTS The fluids commonly used in refrigerating and air conditioning equipment to create the cooling effect. These fluids can damage the environment.

FORCED AIR A distribution system in which a fan circulates air from the heating or cooling unit to the rooms through a network of ducts.

FOSSIL FUEL A naturally occurring carbon or hydrocarbon fuel such as natural gas, propane and oil, formed by the decomposition of prehistoric organisms.

FURNACE A heating unit that uses a forced air distribution system.

GROUND SOURCE HEAT PUMP Another term for an Earth Energy System.

HEAT EXCHANGER A structure that transfers heat from one gas or liquid to another gas or liquid. For example, the hot combustion gases in a furnace to the circulating household air or, in a boiler, to the circulating hot water.

HEAT RECOVERY VENTILATOR (HRV) A device used in central ventilation systems to reduce the amount of heat that is lost as household air is replaced with outside air. As fresh air enters the house, it passes through a heat exchanger heated by the warm outgoing air stream and is preheated.

HIGH-EFFICIENCY (condensing) FURNACE OR BOILER A heating unit with an annual fuel utilization efficiency (AFUE) of 90% or more. It has a second stainless steel heat exchanger that removes additional heat from exhaust gases. Water vapor condenses as the exhaust cools. The unit vents through a narrow plastic wall pipe instead of a chimney.

HYDRONIC SYSTEM A distribution system in which hot water is circulated through a network of pipes to radiators, wall panels or an under-floor heating system.

INSTALLED COST The total of the purchase price and the installation costs of equipment.

INSTANTANEOUS WATER HEATER A device that heats water as required but does not store it. The unit is usually located near the point of use.

INTEGRATED (combo) HOT WATER SYSTEM A system that provides both space and water heating from a single heat source.

KILOWATT A unit of electrical power used to measure the heating capacity of electric equipment. One kilowatt (kW) equals 1,000 watts (W).

MID-EFFICIENCY NATURAL GAS OR PROPANE FURNACE OR BOILER A gas heating unit with an annual fuel utilization efficiency (AFUE) of 78 to 82%. Some models exhaust through the basement wall.

NEW OIL FURNACE Efficiencies (AFUE) range from 78 to 86%. Has flue gases that may be exhausted through a chimney or a side wall vent.

R-2000 A performance standard for new homes under a voluntary government/industry program. Builders meet the standard by offering an integrated package of features designed to meet the R-2000 requirements. The package includes high insulation levels, air-tightness, heat recovery ventilation and efficient heating/cooling systems.

RETROFIT Replacement of one or more components of an existing system.

SEASONAL EFFICIENCY A performance rating that considers the heat (or ‘cool’) actually delivered to the living space, the total energy available in the fuel consumed, and the impact the equipment itself has on the total heating or cooling load through an entire heating or cooling season. HSPF, AFUE, SEER and EF are seasonal efficiency ratings.

SEER seasonal energy efficiency ratio

SETBACK THERMOSTAT A programmable thermostat with a built-in timer. You can adjust it to vary household temperature automatically.

SPACE HEATER A heating unit that supplies heat directly to the room where it is located and is not connected to a distribution system.

STORAGE-TYPE WATER HEATER A tank that heats and stores hot water.

TON A measure of the cooling capacity for central air conditioners and heat pumps.