AFUE% - "Annual Fuel Utilization Efficiency" is a measure of how efficient the furnace is over an entire heating season. The higher the number, the more usable heat you will get for every unit of fuel. A furnace with an AFUE of 80% will provide 80 cents worth of heat for every dollar of fuel. The government's established minimum AFUE rating for furnaces is 78%. For example, an AFUE of 90 means that 90% of the fuel is being used to warm you home, while the other 10% escapes as exhaust with the combustion gases.

Air Handler - The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. In some systems a furnace handles this function.

Balance Point - An outdoor temperature, usually between 30 degrees F and 45 degrees F, at which a heat pump's output exactly equals the heating needs of the home. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

BTU - British thermal unit. The amount of heat required to raise the temperature of one pound of water (about one pint) by one degree F.

Capacity - The ability of a heating or cooling system to heat or cool a given amount of space. For heating, this is usually expressed in BTU’s. For cooling, it is usually given in tons.

CFM - Stands for Cubic Feet per Minute. A measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air is being forced through the system.

Compressor - Part of a split system heat pump or air conditioner’s outdoor unit that controls the pressure applied to the refrigerant, necessary for taking in heat to warm your home or getting rid of heat to keep your home cool.

Condenser Coil - Part of a split-system air conditioner or heat pump. By converting refrigerant that is in a gas form back to a liquid, the coil sends heat carried by the refrigerant to the outside.

Damper - A type of "valve" used in ductwork that opens or closes to control airflow. Used in zoning to control the amount of warm or cold air entering certain areas of your home.

Down-flow - A type of furnace that takes cool air from the top and blows warm air to the bottom - common when your furnace must be located in a second-floor closet or utility area.

Electronic Air Cleaner (EAC) - An electronic device that filters out large particles and contaminants in indoor air. It then electronically pulls out tiny particles that have been magnetized, such as viruses and bacteria, drawing them to a collector plate.

Load Estimate - A series of studies performed to determine the heating or cooling requirements of your home. An energy load analysis uses information such as the square footage of your home, window and door areas, insulation quality and local climate to determine the heating and cooling capacity needed by your furnace, heat pump or air conditioner.

Evaporator Coil - Part of a split system air conditioner or heat pump located indoors. The evaporator coil cools and dehumidifies the air by converting liquid refrigerant into a gas, which absorbs the heat from the air. The warmest refrigerant is then carried through a tube to the outdoor unit (condenser coil).

Fan Coil - An indoor component of a heat pump or air conditioning system, used in place of a furnace, to provide additional heating on cold days when the heat pump does not provide adequate heating. It is usually backed up with an electric element.

Geothermal - Geothermal means "heat from the earth". A geothermal system is a heat pump which absorbs heat from either the ground or from water pumped from a well or pond. Both the ground and ground water tend to be warmer in the winter than outdoor air, enabling the system to operate more efficiently and less expensively.

Heat Pump - An air conditioner that contains a reversing valve that allows it to alternate between heating and cooling.

Heat Source - A body of air or liquid from which heat is collected. Heat pumps utilize the air outside the home which is used as the heat source during the heating cycle. Boilers utilize hot water as a heat source through fan coils or baseboard coils.

Horizontal Flow - A type of furnace, installed on its "side," that draws in air from one side, heats it and sends the warm air out the other side. Most often used for installations in attics or crawl spaces.

Humidifier - A piece of equipment that adds water vapor to heated air as it moves out of the furnace. This adds necessary moisture to protect your furnishings and reduce static electricity.

HSPF - The Heating Seasonal Performance Factor is a measure of the heating efficiency of a heat pump. The higher the HSPF number, the more efficiently the heat pump heats your home.

Matched System - A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together, and used according to design and engineering specifications.

Operating Cost - The day-to-day cost of running your home comfort equipment, based on energy use.

Outdoor Coil/Condensing Unit - The portion of a heat pump or central air conditioning system that is located outside the home and functions as a heat transfer point for collecting heat from and dispelling heat to the outside air.

Payback Analysis - Overall measure of the efficiency and value of your home comfort system. By combining your purchase price and ongoing operating costs, a payback analysis determines the number of years required before monthly energy savings offset the purchase price.

Reclaiming - Returning used refrigerant to the manufacturer for disposal or reuse.

Reciprocating Compressor - A type of compressor used in air conditioners that compress refrigerant by using a type of "piston" action.

Recycling - Removing, cleaning and reusing refrigerant.

Refrigerant - A chemical that cools air as it evaporates. Air conditioning systems use Refrigerant in the Evaporator Coil to cool air as it passes by.

Refrigerant Lines- Two copper lines that connect the Condenser (Outdoor) Coil to the Evaporator (Indoor) Coil.

Scroll Compressor - A specially designed compressor that works in a circular motion versus an up and down piston action like a reciprocating compressor.

SEER - Seasonal Energy Efficiency Ratio. A measure of an air conditioner's cooling efficiency. The higher the number, the more efficient the unit and the lower the operating cost. The government's established minimum SEER rating for air conditioners is 10. For new central systems, SEERs of 12 or higher are generally considered high-efficiency units. As of January 23rd 2006, the minimum SEER rating will be 13.

Single Package - A year-round heating and air conditioning system that has all of the components completely encased in one unit outside the home. These are more common in a commercial application, also known as Rooftops.

Split System - A heat pump or central air conditioning system with components located both inside and outside the home. The most common design for home use.

Supplementary Heat - The auxiliary or emergency heat, usually electrical resistance heat, provided at temperatures below a heat pump's balance point.

Tank-less Water Heater – A tank-less or on-demand water heater is a small heating unit located close to the point of use, which heats the water just before it is used. These units have no storage capability, and are usually not well suited for "whole house" use, as multiple units are typically needed.

Thermostat - Unit that monitors and controls your HVAC system products.

Ton - A ton is a measure of the size or cooling capacity of an air conditioner. One ton is equivalent to removing 12,000 BTUs of heat per hour. For example, a three ton air conditioner can remove 36,000 BTUs per hour.

Up-flow - A type of furnace that draws cool air from the bottom and blows the warmed air out the top into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.

Ventilator - A ventilator captures heating or cooling energy from stale indoor air and transfers it to fresh incoming air.

Zoning - A way to increase your home comfort and energy efficiency by controlling when and where heating and cooling occurs in a home. Programmable thermostats are used to control operating times of the equipment. Dampers are used to direct airflow to certain parts or "zones" of the home.