A/C Efficiency Ratings and What to Look for When Buying New Cooling Equipment

August 26, 2014
Ross and Witmer

When you’re choosing new cooling equipment, the A/C efficiency ratings can help you identify the best system for your home and budget. The U.S. Department of Energy (DOE) requires all cooling equipment to prominently display the relevant ratings for each type. The terms include SEER (seasonal energy efficiency ratio), EER (energy efficiency ratio) and COP (coefficient of performance).

What Efficiency Ratings Mean

  • SEER refers to the seasonal efficiency of central cooling systems. The minimum starts at 13 and systems are available that go into the 20s. Engineers test the SEER by running a system for period equivalent to a season and measuring the amount of electricity it uses to cool a space to 80 degrees when the outdoor environment is held at 82 degrees.
  • The EER is similar to SEER, but the testing period is of a shorter duration at a higher temperature. Instead of 82 degrees, the equipment is tested at 95 degrees. Portable and window air conditioners¬†must prominently display the EER, while manufacturers of central systems don’t have to, although the EER is always available. The minimum for portable equipment is 9.7. It’s important to pay attention to the EER, since the rating indicates how well it cools under more typical summer temperatures.
  • The last of the A/C efficiency ratings is the COP. This rating is more commonly found on heat pumps for the heating efficiency, but it’s available for cooling systems, as well. The concept behind the COP is to reveal how much heat the system removes for each unit of energy it uses. The least efficient systems move one unit of heat per unit of energy consumed.You can calculate the COP by dividing the EER by 3.41. A system with an EER of 10 has a COP of 2.93, which means it moves nearly three times the heat per unit of energy used.

To learn more about A/C efficiency ratings and system selection, contact Ross & Witmer. We’ve provided exceptional HVAC services for Charlotte, Union, Mecklenburg and Gaston homeowners since 1945.

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