Annual Fuel Utilization Efficiency. The AFUE percentage tells you how much energy is being converted to heat. The higher the number, the greater the efficiency.

The portion of your heating and cooling system that forces air through your home's ductwork.

British Thermal Units. The amount of heat it takes to raise one pound of water one degree Fahrenheit. The higher the BTU rating, the larger the heating capacity of the furnace or air conditioner.

The ability of a heating or cooling system to heat or cool a given amount of space. Heating is usually expressed in BTUs; cooling is expressed in tons.

The Air Conditioning, Heating and Refrigeration Institute (AHRI) puts heating and cooling equipment through rigorous certification processes to ensure systems deliver the promised performance at certain test conditions.

The Air Conditioning, Heating and Refrigeration Institute (AHRI) puts heating and cooling equipment through rigorous certification processes to ensure systems deliver the promised performance at certain test conditions.

The motor/pump that drives the air conditioning unit. It is responsible for pumping refrigerant throughout the system.

Part of the outdoor portion of a heating or cooling system, which releases or collects heat from the outside air.

Part of the outdoor portion of a heating or cooling system, which releases or collects heat from the outside air.

Part of the outdoor portion of a heating or cooling system, which releases or collects heat from the outside air.