what does seer rating mean?

Understanding Efficiency Ratings

Understanding the rating methods used and how they apply to you is not difficult. A simple review of these terms can help you to make more informed buying decision. The terms that are used are:

• SEER - Seasonal Energy Efficiency Ratio This rating is used to compare electrical power consumption of an air conditioning unit and evaporator, like MPG on your car. A minimum SEER rating of 13 is required by the Dept Of Energy's new standard for all equipment manufacturers.

• AFUE - Annual Fuel Utilization Efficiency This rating is used to rate the gas consumption of a natural gas furnace. A minimum AFUE rating of 80% is required for all gas heating systems.

• CFM - Cubic Feet Per Minute The method of measuring air volume for fans and ducts. SEER ratings are based on air volume of 400 CFM per ton of air conditioning.

• BTU - British Thermal Unit Measurement of cooling or heating capacity. 12000 BTU's equal one ton of air conditioning. As an example a 4-ton air conditioner would have a capacity of 48000 BTU's.

The efficiency of the equipment or SEER rating is determined by the ratio of power consumption to actual BTU output of a given system. The higher the SEER or AFUE rating the less power or gas is used. In theory a 14 SEER air conditioning unit would operate at half the cost of a 7 SEER device or unit.

The question one must ask though is simply this. Does the unit actually perform to the SEER rating the manufactures claim? Should I simply find a unit with a high SEER rating and expect dramatic reduction in my light bills for years to come? The answer is sometimes but more often not.

The ratings of the equipment were calculated in a laboratory setting. There were no allowances made for the air duct system, no consideration for the actual installation, or the building in which it is installed. SEER ratings are based on the assumption that the air conditioning system is correctly installed in the home with a properly designed and installed duct system that is capable of delivering the standard 400 CFM per ton air volume.

Systems that are installed to old, deteriorated, and improperly sized ducts do not even come close to delivering the rated system efficiency. Proper installation of ductwork, grilles, refrigerant piping and system startup procedures are essential for a reliable energy efficient operation.

These ratings may be a good way to compare manufacturers cooling or heating equipment but are not reflective of how the system will actually perform in your home. There is a lot more to consider in the selection of a quality comfort system than SEER ratings alone.