What Temperature Should You Set Your AC to in Summer?

There’s no single “right” number that works for every home, but there is a sweet spot most Orange County households land on: around 78 F when you’re home, and 82-85 F when you’re out. That balances real comfort against your energy bill and the wear on your system. Here’s how to think about it, and why cranking it lower doesn’t do what people expect.

What’s the short answer? Aim for 78 F

The U.S. Department of Energy points to 78 F as an efficient setting while you’re home and awake. It sounds warm on paper, but paired with fans and normal summer clothing it’s comfortable for most people, and here’s the key: the smaller the gap between your indoor setting and the hot air outside, the less your AC has to run. Every degree you drop meaningfully raises your cooling cost, because the system works harder and longer to hold it.

If 78 feels too warm for your household, that’s fine – set it where you’re comfortable. Just know that 74 costs noticeably more than 78, and 70 costs more still.

What should I set it to when I’m away?

Bump it up to 82-85 F when the house is empty. You’ll cut cooling costs during the hours no one’s benefiting from them. One caution for Orange County: don’t shut the AC off entirely on hot days. A house that’s baked all afternoon forces the system to work overtime to recover, and letting indoor humidity climb can invite mold and musty smells. A setback, not a full shutoff, is the move – and a programmable or smart thermostat automates the whole thing. If yours is old or unreliable, our thermostat service can sort out repair vs. upgrade.

Does a lower setting cool the house faster?

No – this is the most common myth. Setting the thermostat to 65 when you walk into a hot house does not cool it any faster. Your AC moves heat at a fixed rate no matter what number is on the display; a lower setpoint just makes it run longer (and risks freezing the coil). Set it to your target and let it work.

A simple summer plan

• Home & awake: around 78 F
• Sleeping: a couple degrees cooler if it helps you rest
• Away: 82-85 F (setback, not off)

Worth knowing: the DOE points to 78 F as an efficient summer setting, and setbacks while you’re away can cut cooling costs – the AC simply runs less when the indoor-outdoor gap is smaller. (Source: U.S. Dept. of Energy, Thermostats.)

Does coastal vs. inland Orange County change the number?

Where you live changes the feel. Inland homes – Irvine, Santa Ana, Anaheim – take a bigger afternoon heat load, so the system runs hardest from mid-afternoon on; a smart thermostat that pre-cools slightly before the peak can help. Coastal homes stay milder but more humid, so comfort is as much about humidity as temperature.

What if your AC can’t hold the setting?

Here’s the useful tell: if your AC runs constantly and still can’t reach a reasonable setpoint on a hot day, that’s not a thermostat problem – it usually means low refrigerant, a dirty coil, or an undersized system. Get it checked through our AC repair service before the next heat wave rather than fighting it with the thermostat.

We keep Orange County homes comfortable and efficient – and if your system is struggling to hold its setting, we’ll find out why. Reach out here.

Frequently asked questions

Is 72 F too low?

Not “wrong,” but it costs noticeably more than 78 and makes the system work harder. It’s a comfort-vs-cost tradeoff.

Should I turn the AC off when I leave?

In OC heat, a setback (82-85 F) beats a full shutoff – shutting off lets the house bake and humidity climb, forcing a hard recovery.

What’s the best sleeping temperature?

Many people sleep best a couple degrees cooler than their daytime setting; adjust to taste.

Does a smart thermostat really save money?

Yes – mainly by automating setbacks you’d otherwise forget. The savings come from not cooling an empty house.