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How energy efficient are window air conditioners compared to a split system whole-house air conditioner?
Sunday, December 19, 2021
If you determine energy efficiency based only on the EER (Energy Efficiency Rating) numbers, window air conditioners score lower on average than a split system. Older window units, or recently purchased less-expensive ones, have an EER of about 9. More efficient (and more expensive) ones hover around a 12 EER, and the newer inverter-type window units are up at 15. The low EER of many window units is due to the fact that there is no minimum EER (or similar SEER) required by the government, and lower efficiency units are cheaper to produce.
New split system air conditioners, on the other hand, are mandated to be minimum 14, with some models rated at over 20. To give you an idea of the difference: a 20 rating uses half as much electricity as a 10 for the same amount of cooling. Most window air conditioners are also less efficient at dehumidification—an important factor for indoor comfort—than a split system.
Do Window Air Conditioners Use Too Much Electricity?
Most window air conditioners use about 1/3 more electricity per BTU of cooling than an average split system. But if you consider other factors, window units gain ground and may even be more cost efficient in some situations:
•• Window air conditioners can serve just one room. If you have a sun room that is only cooled occasionally, a window unit means the central HVAC does not have serve it year-round, or contend with the air leakage and back-pressure on the ducts from a closed vent when not in use. And a single person or couple that just uses one bedroom can choose to cool only that room overnight.
•• Good for locales that only need cooling briefly in the summer, like the Pacific Northwest, and can be removed at end of season.
•• No ducts, so no “duct loss.” Even brand-new and well-sealed ducts will warm the air several degrees in transit to rooms distant from the air handler. Older, leaky ducts even more.
Ductless mini-split air conditioners share all of these advantages and are much more energy efficient. They are also whisper quiet, a big plus compared twindow units. But mini-splits are way more expensive, and difficult to install for the average homeowner. Low cost and easy installation are the two big advantages that make window air conditioners always popular.
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To learn more about heating and air conditioning systems, see these other blog posts:
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