Window A/C or central A/C – which is more efficient?


Air conditioning uses a lot of energy in the average American home. This translates to significant carbon emissions for the environment and high energy bills for consumers.

According to the American Council for an Energy-Efficient Economy, residential air conditioning accounts for about 5 percent of the electricity used in the U.S. Considering that a lot of electricity is consumed by the commercial and manufacturing sectors, it is safe to assume that A/C is an even bigger portion of the average U.S. home energy bill.

So, which is more efficient, investing in a window A/C unit or central A/C? The issue is more complicated than it appears.

According to, central A/C units are technically more efficient, with top energy-efficiency ratings of 14 to 15. By comparison, the highest-rated window units go up to 10 or 11. It would appear from this that central A/C is better, but this does not take the full picture into account.

Even though central air conditioners are more efficient, homes that use window A/C units use less energy on average than homes with central A/C, the source explained. A central air conditioner cools the whole house, while a window air conditioner only cools one room. This means that on those hot nights that demand the A/C be kept running, there is significantly less overall energy being used.

Another important factor is that central A/C makes very little noise. This may seem irrelevant, but window A/C units almost always get turned off when homeowners leave the house – window A/C units do not. The ducts used to pump cool air around the house are also another variable for loss.

On the other hand, smart thermostats are becoming more popular in modern homes, which may lead central A/C units to be more efficient in real terms.