Is running a window AC overnight expensive?
Yes, running a window AC overnight is just as expensive as running your unit at any other time. You will end up paying more on your monthly electric bill if you leave your AC running overnight.
Most window ACs consume 900 – 1,400 watts of electricity an hour. One kilowatt of electricity costs $0.23 at current market rates in the US. The historical average is closer to $0.13.
That means that every hour you run your window AC during the night you are paying $0.21 – $0.36 for the privilege. Over the course of an 8-hour night, the window AC will cost you $1.68 – $2.88.
There’s a misconception on some internet forums that running a window AC continuously is more efficient because your air conditioner expends more energy bringing your home up to temperature than it would maintaining a specific temperature.
But this isn’t how air conditioners work. Most air conditioning systems have a fixed output and will turn on or off depending on whether the temperature in your home is too hot or in an acceptable range.
That means you pay a flat rate whenever you put your air conditioner on. More time means a higher electric bill no matter the circumstances.
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Mark is a journalist who has written about home products for two years. He holds a masters degree with distinction from the London School of Economics and an undergraduate degree from the University of Edinburgh.