How High Should You Set Your AC While You're on Vacation?

By Michael Franco

August 30, 2025

Heading out for a summer getaway? Before you grab your suitcase and lock the front door, take a moment to consider your thermostat. Adjusting your air conditioning while you’re away is a simple way to save money and energy — but crank it too high (or turn it off entirely), and you could return to a house full of unpleasant surprises.

This May Also Interest You: 10 Ways to Make Your Central Air Conditioner More Efficient

So, what’s the right temperature setting when you're not home? The answer lies in finding the sweet spot between energy efficiency, protecting your home, and maintaining indoor air quality.

Finding the Most Energy-Efficient Thermostat Setting

If you’re leaving your house for more than a day or two, the U.S. Department of Energy recommends setting your thermostat 7 to 10 degrees Fahrenheit higher than your usual temperature. In most cases, that means somewhere between 80 degrees F and 85 degrees F while you're away during the summer.

That range reduces your cooling costs without letting your house get uncomfortably hot — or worse, causing heat-related damage to electronics, food items in your pantry, or wood furniture. The idea is to cut back on unnecessary cooling while keeping the house from becoming a sauna.

Should You Turn Off the AC Completely?

It’s tempting to shut everything down and eliminate cooling costs altogether. But turning your air conditioner completely off during hot, humid months is generally not a great idea — especially in areas where summer temperatures soar past 90 degrees F and humidity is high.

An overheated home can lead to more than discomfort:

Humidity build-up can cause mold and mildew, particularly in basements, bathrooms, or closets.
Wood floors and furniture may warp or crack if the indoor temperature and moisture levels fluctuate too much.
Appliances and electronics can suffer in extreme heat, particularly if they’re located in enclosed or poorly ventilated areas.

If you're gone for a weekend and live in a dry, mild climate, turning off the AC might be fine. But for longer trips or if you live in a hot and humid region, keeping the air conditioner on — just at a higher setting — is usually the smarter move.

Will a Higher Setting Help Prevent Mold?

Absolutely. Mold loves moist, stagnant air — especially when it's paired with warmth. Setting your thermostat around 82°F to 84°F while you're away allows your AC to run just enough to keep humidity levels in check and discourage mold growth.

If your thermostat has a humidity control feature, aim to keep the indoor humidity under 60% to reduce the risk of mold growth. You can also boost your defenses by:

Leaving interior doors open so air can circulate
Running ceiling fans on low settings
Using a dehumidifier if your area tends to be very humid

For particularly mold-prone homes (think basements or beach houses), keeping a close eye on both temperature and humidity is essential.

What’s a “Safe” AC Temp for Your Home?

“Safe” can vary depending on your home, climate, and what’s inside. Generally, 78°F to 85°F is a safe range that balances protection and energy savings. This range ensures:

Materials inside your home stay stable
Pets or plants (if left behind) aren’t harmed
Mold and mildew have a harder time developing
Energy usage is dramatically reduced

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Do Smart Thermostats Adjust Automatically?

If you have a smart thermostat, you're in luck. Many models now include a “vacation” or “away” mode that automatically adjusts your temperature settings when you leave — and some even learn your habits over time to make intelligent guesses about when the house is unoccupied.

Most smart thermostats let you control the temperature remotely using an app, so if you forget to make changes before heading to the airport, no worries — you can log in and adjust your settings from anywhere.

Some advanced models can:

Monitor indoor humidity and alert you if it rises too high
Return to your preferred temperature just before you get home
Integrate with smart home systems to coordinate with blinds, fans, and dehumidifiers

Smart thermostats are particularly useful if your summer plans change frequently or if you tend to forget to adjust settings manually.

Final Thoughts

Before heading out on vacation, take a few minutes to raise your thermostat to a smarter setting. You’ll protect your home, cut down on cooling costs, and return to a space that’s still comfortable — not stuffy. If you have a smart thermostat, activate vacation mode or set a custom schedule that matches your travel dates.

By keeping your home just cool enough to stay safe and dry, you'll give your AC a break without coming home to a moldy mess or soaring energy bills.

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