Homeowner cuts $500 power bill to $70 by opening windows at night, but humid climates push back

A homeowner on the r/Frugal subreddit says a simple overnight cooling routine helped cut an electric bill from $500 to as little as $70 a month.

What happened?

Trying to shrink what they described as an unusually high $500 power bill, the solo occupant of a 950-square-foot, two-bedroom home revealed that they began leaving the thermostat at 60 degrees Fahrenheit when they were away. Once spring arrived, they said, they stopped running it altogether.

They didn't even have to do anything initially to keep a comfy temperature. That didn't last forever, though.

"Last couple weeks it reached 75-79 (too hot) so I open windows at night for 67-72 air and close them in the morning," they wrote. "My bills have consistently gone down to $70-$100 a month!"

The homeowner did add, "I acknowledge this wouldn't work in more extreme climates."

Why does it matter?

Where nights cool off substantially and the air stays relatively dry, a house can hold onto that overnight chill after the windows are shut in the morning. That in effect stores some of the coolness in the structure and easing the need for daytime AC.

Still, commenters were quick to note that climate matters.

That logic can flip in humid states such as Texas and Florida, commenters said, because opening windows overnight may pull damp air inside. The added moisture can make a home feel stickier and, if humidity stays too high, could raise mold concerns.

Some readers focused less on the window routine and more on the size of the bill, saying $500 to cool a 950-square-foot home could signal larger efficiency problems, including poor insulation, air leaks, or an aging AC system that needs service.

What are people saying?

Despite its drawbacks in other areas, many commenters backed the strategy while offering tweaks of their own.

"You can also put a box fan in the window to pull cool air in at night for extra benefit," one wrote. "I live in a moderate climate area and I use this tactic for the small number of days it gets hot here."

Others said humidity changes everything for those not lucky like the OP to live in a climate with dry air.

"It's not so much the heat that kills me, it's the humidity (Texas) and that's not really addressable with opening windows," they said. "We have dehumidifiers that run 24/7 and make keeping the house at 74 feel alright."

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