Energy Efficiency and Window Air Conditioners

With unpredictable energy costs you’ll want to be sure to select the most efficient unit for the space you need to cool. This requires becoming familiar with a few key terms:


BTU refers to British thermal unit which is defined by the amount of energy required to raise the temperature of a room by a degree. While this is a good measurement to determine the power of the air conditioner, other factors need to be considered when purchasing a unit.

  • Size of the room being cooled (in square feet)
  • Volume of the room (rooms with higher ceilings have more volume than rooms with low ceilings)
  • Ambient Temperature compared to desired temperature (how many degrees does the unit need to cool the air)
  • Other Factors:
    1. Is the unit on the side of the house facing the sun?
    2. How many people are in the room?
    3. Are other heat sources in the room such as appliances and electronics?

What does ENERGY STAR mean?

ENERGY STAR is a government-supported program that promotes the protection of the environment through efficiency in home appliances. Products that are labeled with an ENERGY STAR rating have passed the strict energy efficiency guidelines determined by the EPA and the U.S. Department of Energy. Certified Energy Star room air conditioners are at least 10% more energy efficient than other units.


“EER” stands for Energy Efficiency Rating. The EER of an air conditioner can be found by dividing the BTU capacity by the wattage. The EER tells you the cooling capacity of the unit from a given amount of electricity. Choosing a higher EER will give you a more energy efficient air conditioner. Look for units with an EER of 10 or higher. Energy Star air conditioners have an EER rating of 10.7 or above.

“SEER”, or Seasonal Energy Efficiency Rating, is used to measure the efficiency of Mini-Split and Central Air units. While similar to EER, the SEER of an air conditioner is determined by dividing the annual BTU by the total watt hours. Look for units with a SEER of 12 or higher.

When comparing two similar units with the same BTU ratings, the unit with the higher EER or SEER rating may have a higher cost than the lower rated unit. However, the more efficient unit with the higher EER or SEER will cost less in energy consumption over the lifetime of the unit.

Kara Zorn

About Author

Kara Zorn is a wife and working mom who loves life hacks that help her schedule allow for as much quality family time as possible. She enjoys cooking with locally sourced food and produce and recently took up brewing Kombucha.

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