What temperature should you set your AC to save money?

The single biggest lever on a summer electric bill is the number on the thermostat — bigger than any filter change or weekend of caulking windows. Here's what the setting actually does to your cost, and the habits worth changing.

The rule of thumb

The U.S. Department of Energy's standard guidance is 78°F when you're home and awake, higher when you're out or asleep. Every degree above that you're used to holding cuts cooling energy by roughly 6-8%. Going from 72°F to 78°F — a common gap — can mean a 25-35% drop in AC runtime over the summer.

That's a starting point, not a rule: humidity, sun exposure and personal tolerance all shift where "comfortable" actually sits for your house.

Why cranking it down when you walk in costs more, not less

Setting the thermostat to 65°F to cool a hot house "faster" doesn't make the system work faster — most residential units cool at a fixed rate regardless of the target. All a lower setpoint does is keep the compressor running longer after the room is already comfortable, because it won't stop until it hits that number. Set it to the temperature you actually want and leave it.

Let it drift when no one's home

A programmable or smart thermostat that lets the house rise 4-7°F while you're at work, then cools back down before you're back, saves real money over keeping it cold all day. This is different from the old "just leave it running at one temperature all day is more efficient" myth — for AC specifically, setback saves energy, because a warmer house loses less heat into the outside air per hour, so there's less to remove overall.

Sleep settings

78-80°F feels warm to sit still in, but most people sleep fine 2-4°F above their daytime comfort setting, especially with a fan running. If summer electric bills are painful, this is one of the lower-effort changes available.

Combine it with airflow, not just the number

A ceiling or box fan doesn't cool the air, but the wind-chill effect on skin lets most people feel comfortable 3-4°F warmer than they would sitting still. Run fans only in occupied rooms — they add nothing in an empty one and just use extra electricity.

See it in dollars, not degrees

The abstract "6-8% per degree" is easier to act on once it's a number. Put your AC's size and your new daily hours into the AC electricity cost calculator at your state's rate, and compare a 72°F routine against a 78°F one to see the actual monthly gap.