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The original was posted on /r/lifeprotips by /u/Isa-Me-Again on 2026-07-19 15:00:56+00:00.
::tldr:: if your central AC unit is struggling to keep your house cold and it takes long into the night to cool it back down after a hot day, a window AC unit may lower your electricity bill by reducing the workload of the central AC unit and allowing it to shut off earlier at night, and allows it to take breaks throughout the day.
Now for the long version lol. My electricity bill went down roughly 10% comparative to last years bill from the same month after buying a window AC unit.
Before the new unit, my central AC struggled during the summer to keep the house cool. I live in Lynchburg, Virginia where the summers are humid, and this one is particularly warm. Even with the central AC on, during the hottest part of the day the inside of the house would get up to 86°(30°c) and the central unit would continue pumping all day and not have the house cooled to 74° until about midnight.
Cut to this year where I was prepared for it and bought a window AC unit to help the hottest part of the house stay cooler. The Unit is a little 6,000 BTU meant to cool off my work-from-home office that had terrible airflow from the AC. I fully expected my bill to go up some, but I was okay with that for the comfort.
What I was not prepared for was my entire house staying at 74° the entire day and my bill going down. After contemplating what happened, it appears that the AC is able to shut off and on throughout the day rather than pumping the entire day, as well as the house not needing to cool down until midnight, as it needed to previously.
I hope this helps someone if they are in the situation I was in. Thank you for reading. Have a good one!