Everything You Want To Know About SEER

The efficiency of air conditioners is often rated by the Seasonal Energy Efficiency Ratio (SEER) which is defined by the Air Conditioning, Heating and Refrigeration Institute in its standard ARI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.

The SEER rating of a unit is the cooling output in Btu (British thermal unit) during a typical cooling-season divided by the total electric energy input in watt-hours during the same period. The higher the unit's SEER rating the more energy efficient it is…

Air conditioner sizes are often given as "tons" of cooling, where 1 ton of cooling equals 12,000 BTU/h (3.5 kW). 1 ton of cooling equals the amount of power that needs to be applied continuously, over a 24 hour period, to melt 1 ton of ice. The annual cost of electric energy consumed by a 72,000 BTU/h (21 kW) (6 ton) air conditioning unit, operating for 1000 hours per year, with a SEER rating of 10, and an electric energy cost of $0.12 per kilowatt-hour (kW·h) is:

(72,000 BTU/h) × (1000 h) × ($0.12/kW·h) ÷ (10 BTU/W·h) ÷ (1000 kW/W) = $864

The Seasonal Energy Efficiency Ratio (SEER) has the same units of Btu/W·hr, but instead of being evaluated at a single operating condition, it represents the expected overall performance for a typical year's weather in a given location. The SEER is thus calculated with the same indoor temperature, but over a range of outside temperatures from 65 to 104 degrees F, with a certain specified percentage of time in each of 8 bins each spanning 5 degrees F. There is no allowance for different climates in this rating. It just gives an indication of how the actual EER is typically affected by different outside temperatures over the course of a cooling season.

SEER rating more accurately reflects overall system efficiency on a seasonal basis and EER reflects the system’s energy efficiency at one specific operating condition. Both ratings are useful when choosing products, but the same rating must be used for comparisons. As of January 2006, all residential air conditioners sold in the United States must have a SEER of at least 13. ENERGY STAR qualified Central Air Conditioners must have a SEER of at least 14.

With existing units that are still functional and well-maintained, when the time value of money is considered, retaining existing units rather than proactively replacing them may be the most cost effective. However, the efficiency of air conditioners can degrade significantly over time. Therefore, maintenance (such as cleaning the coils) should be performed regularly to keep their efficiencies as high as possible.

But when either replacing equipment, or specifying new installations, a variety of SEERs are available. For most applications, the minimum or near-minimum SEER units are most cost effective, but the longer the cooling seasons, the higher the electricity costs, and the longer the purchasers will own the systems, the more that incrementally higher SEER units are justified. Residential split-system AC units of SEER 20 or more are now available, but at substantial cost premiums over the standard SEER 13 units. The higher SEER units typically have larger coils and multiple compressors, the cost reflects the additional complexity.

If SEER is all Greek to you that is OK,  Give Aaron’s Mechanical Service a call at 623-388-4436 for the right advice on your AC Unit!

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Aaron’s Mechanical Services
623-388-4436
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