May 16, 2012
“How much does it cost to run an air conditioner?” A very important question when choosing a cooling appliance. Manufacturers answer that question with “SEER”, or Seasonal Energy Efficiency Ratio. It is a mathematical formula to which the solution is a ratio of BTUs of cooling output to watts of electricity input over the course of a cooling season. Put more simply, it’s kind of like figuring the mileage a new car will get.
The mileage sticker on the window is a reference point. A car’s mileage is effected by how you drive: How fast you accelerate and decelerate, how much driving in town and how much on the highway, whether or not you use the cruise control and the overdrive or the four wheel drive.
The SEER rating on an air conditioner is like that reference point. The efficiency of an air conditioner depends largely on how you use it. Do you use a manual thermostat or a smart, programmable thermostat? Do you minimize doorway usage to keep outdoor air outdoors? Do you like to keep the house at 68 degrees or 73 degrees? Proper periodic maintenance also directly effects the system efficiency. Making sure the refrigerant is properly charged, the coil and filter are clean to allow sufficient air flow and the ducts are sealed will improve efficiency and reduce operating cost.
The advertised SEER rating is calculated in a laboratory under nearly ideal conditions. This is why the specifications will always say “up to” before the rating. Real life efficiency, like real life mileage of a car, will vary from the sticker number. But a system rated at 17 SEER will be more efficient than one rated at 13 SEER.
Today, it is rare to see systems rated below SEER 9 in the United States because aging, existing units are being replaced with new, higher efficiency units. The United States requires that residential systems manufactured after 2005 have a minimum SEER rating of 13.
Energy savings can be significant with more efficient systems. For example, by upgrading from an old SEER 9 to SEER 13, the power consumption is reduced by 30%. That can result in an energy savings up to $300 per year depending on the usage rate and the cost of electricity.




