When purchasing a heat pump or air conditioner, consumers are often overwhelmed by the array of efficiency ratings, abbreviations and acronyms used to describe or explain the products. Read on to help lessen the mystery of purchasing a home comfort system.


Heating, ventilating and air conditioning…refers to the indoor comfort industry.


Air-Conditioning Heating and Refrigeration Institute refers to a non-profit, voluntary organization comprised of heating, air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners to provide you with a standardized measure of comparison. So, AHRI ensures a level of quality within the industry.


The Department of Energy is a federal agency in charge of setting industry efficiency standards and monitoring the consumption of energy sources.


A watt is a unit of energy. It measures the amount of power an electrical appliance uses.

Kilowatt (KW)

A kilowatt equals 1,000 Watts. A kilowatt hour (kWh) is the amount of kilowatts of electricity used in one hour of operation of any equipment.


British thermal unit is the amount of heat that will raise or lower one pound of water by one degree Fahrenheit. A Btuh is how many Btus are used per hour.


Heat pumps and air conditioners are generally sized in tons. Typical sizes for single family residences are between two and five tons. Each ton equals 12,000 Btu’s per hour. The term ton originated when we used to cool or refrigerate with ice. A ton of refrigeration (TR or TOR), also called a refrigeration ton (RT), is a unit of power used in some countries (especially in North America) to describe the heat-extraction capacity of refrigeration and air conditioning equipment. It is defined as the rate of heat transfer that results in the freezing or melting of 1 short ton (2,000 lb; 907 kg) of pure ice at 0 °C (32 °F) in 24 hours.

It is important to note that actual capacity is not constant and will change based on outdoor or indoor temperatures. The published capacity rating of air conditioners and heat pumps is based on performance at the AHRI standards of 95 F outside temperature, 80 F inside dry bulb temperature and 67 F wet bulb temperature. It’s important to note that at 75 F indoors and 50% relative humidity an air conditioner won’t put out its full rated capacity.


Annual Fuel Utilization Efficiency. For furnaces and boilers it’s kind of like miles-per-gallon or MPG for cars. It’s a standard measurement of how efficiently a furnace converts energy from the fuel it uses into warm air for your home.


Seasonal energy efficiency ratio is how we measure the efficiency of an air conditioner, or a heat pump when in the cooling mode of operation. The SEER rating is a measure of the average amount of cooling Btu’s produced by supplying one watt of power to the cooling unit. In the past, a unit with a SEER of 8.00 was considered standard efficiency, and a unit with a 10.00 SEER was considered high efficiency. After January 1, 1992, the minimum SEER required by the DOE changed to 10.00 SEER and 15.00+ SEER was considered high efficiency. As of January of 2006 the minimum air conditioner efficiency has gone to 13 SEER and units are currently available up to 20 SEER.


Heating seasonal performance factor is similar to SEER, but it measures the efficiency of the heating portion of your heat pump. Like SEER, industry minimums have been raised recently, and the minimum is now 6.80 HSPF.


Coefficient of performance compares the heating output of a heat pump per watt of power input to the amount heat you would get from electric resistance heat for the same power input. COPs vary with the outside temperature. As the temperature falls, the COP falls also, since the heat pump is less efficient at lower temperatures. ARI standards compare equipment at two temperatures, 47 F and 17 F, to give you an idea of the COP in both mild and colder temperatures. For clarification, if a heat pump has a COP of 4 that means it will produce 4 times more heat per watt of power input than resistance heat.

Decibel (db)

A decibel describes the relative loudness of a sound. Some common sounds are fairly close to a typical air conditioner or heat pump’s sound level: human voice, 7.0 decibels; blender, 8.8 decibels.

Sound Rating Number (SRN)

Sound is measured in bels (a bel equals 10 decibels). The SRN of a unit is based on ARI test, performed at ARI standard rating conditions. Average sound rating range from 7.0 to 8.0 decibels. The lower the SRN rating, the quieter the unit.

Indoor Coils

A homes air conditioning system consist of two main components the outdoor unit (air conditioner or heat pump) and the indoor coil, or air handler. Combinations of various units will result in different efficiency ratings. Make sure you get a system that is matched and has a AHRI documented efficiency rating.

The Price of Quality

There is more to buying a furnace, heat pump or air conditioner than ratings. The quality of construction and materials used as well as the reliability of the manufacturer and installing contractor can all affect your long-term satisfaction and comfort. Top quality, high efficiency equipment will cost more initially, but it will save you money on utility bills and service calls for years to come. Be sure to weigh all the factors before choosing your new system.