Should You Turn Off Your AC When You Leave for Vacation?

It feels obvious: you are leaving for a week, no one is home, so switch the AC off and stop paying to cool an empty house. In a mild climate, that logic mostly holds. In an Oklahoma August, it can cost you more than it saves, and occasionally a lot more.

The better move is almost never off. It is up. Here is why, and what to actually set. 
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What happens to a closed-up Oklahoma house with the AC off

Turn the system fully off during a 100-degree stretch and your home does not just get warm, it becomes an oven, easily reaching the 90s or higher indoors and staying there day and night. Two things go wrong in that heat:

• Humidity takes over. With no AC running, moisture builds with nothing to remove it. Days of high indoor humidity is how you return to musty air, mildew in closets and bathrooms, warped wood and furniture, and in bad cases mold. Your AC is not just a thermostat, it is your home's dehumidifier, and switching it off stops that job entirely.
• Your stuff suffers. Sustained heat and humidity are hard on electronics, wood instruments, artwork, candles, and anything that melts, warps, or grows mold.

So the "savings" from a week of off can quietly turn into a cleanup, or a repair, that costs far more.
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The answer: set it up, not off

For a summer trip, set your thermostat to around 85°F. That is warm enough to use very little energy while you are gone, but cool enough to keep the house from overheating and to keep humidity in check. You get most of the savings of "off" without any of the risk. If your system has a humidity setting or you run a dehumidifier, keeping humidity below 50 percent matters as much as the temperature.

Do not push it higher than the mid-80s thinking more is better. Past that point you stop saving much more and start letting humidity run wild, which is the exact problem you are trying to avoid.
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A smart thermostat makes this effortless

This is where a smart thermostat earns its keep. You can set the higher "away" temperature, then, from your phone on the drive home, drop it so the house is comfortable when you walk in instead of cooling down for hours after you arrive. Many will also alert you if the indoor temperature or humidity climbs too high while you are gone, which is genuinely useful, since a failure that goes unnoticed for a week is a far bigger problem than one you catch the same day.
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Don't forget the rest of the away checklist

A few things that pair with the thermostat setting:

• Close all blinds and curtains before you leave to block solar heat gain, so the AC barely has to run.
• Consider pets and plants. If anyone or anything living is staying behind, set the temperature for their comfort and safety, not just energy savings.
• Change the filter before a long trip so the system runs efficiently the whole time.
• Don't fully close vents in empty rooms, which can throw off system pressure while you are gone.
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When it's fine to set it higher

The mid-80s guidance is for our summer. If you are traveling in a mild stretch, or leaving for the winter, the calculus changes. But during peak Oklahoma heat, resist the urge to shut it down completely. Set it up, close the blinds, and come home to a house that is dry, sound, and easy to cool back down.

Direct Air is a family-owned Oklahoma City HVAC company, and if you want a smart thermostat that handles all of this automatically, or a quick check that your system is trip-ready, we can help. Learn more about our AC service in Oklahoma City, or contact us before your next trip.
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Serving Homeowners Across the OKC Metro

Direct Air keeps homes comfortable and protected for travelers in Norman, Moore, Oklahoma City, and throughout the area: Edmond, Yukon, Mustang, Midwest City, Del City, Choctaw, Nichols Hills, Newcastle, Purcell, El Reno, and Weatherford, OK.
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Frequently asked questions

Should I turn off my AC when I go on vacation? In an Oklahoma summer, no. Set it to around 85°F instead. Turning it off lets the house overheat and humidity build, risking mildew, mold, warped wood, and damage to electronics, which can cost far more than you saved.

What temperature should I set my AC to when I'm away in summer? About 85°F. It uses very little energy while keeping the home from overheating and controlling humidity. Avoid going much higher, since that lets humidity climb.

Will leaving my AC on while away waste money? Setting it to 85°F uses far less energy than keeping it at your normal comfort temperature, and much less than the cost of the moisture or heat damage that can occur with it fully off.

Can I control my AC from my phone while on vacation? With a smart thermostat, yes. You can set an away temperature, cool the house before you arrive home, and get alerts if the temperature or humidity climbs too high while you are gone.

Should I close the vents and blinds before leaving? Close the blinds to block solar heat so the AC barely runs. Leave vents open, since closing too many can disrupt system pressure while you are away.