The Ideal AC Temperature to Set During a Heat Wave, According to an HVAC Pro

Key takeaways

• For optimal comfort and efficiency during a heat wave, set your thermostat to the highest temperature you find comfortable, typically between 75–78°F.
• A consistent thermostat setting helps your AC run more efficiently and prevents energy waste or wear on the system.
• Smart habits like using fans and closing blinds can keep your home cooler without overworking your air conditioner.

Most people look forward to the warm days of summer — you get to spend more time outside enjoying the fresh air and sun! But when temperatures rise to scorching triple digits, we immediately want to retreat indoors for relief from the heat. In these conditions, it’s natural to want to blast the AC so you can turn your home into an icebox, but it’s not the most energy-friendly or cost-efficient strategy. 

So, if you shouldn't crank down the temperature to achieve Arctic-like conditions indoors, what should you aim for? We decided to ask an HVAC expert for the best temperature you should set your thermostat to during a heat wave, so you can stay comfortable — while conserving as much energy as possible.

Meet our expert

• Elizabeth Shavers, general HVAC and plumbing manager at Oncourse Home Solutions

The best AC temperature to set during a heat wave

The Department of Energy suggests setting your AC to between 75 to 78°F, but ultimately, you should decide what’s best for your household: Their easiest-to-follow advice is to set the temperature to as high as is comfortable when you’re home, and then keeping the home just a little warmer than normal when you’re away.

Elizabeth Shavers, general HVAC and plumbing manager at Oncourse Home Solutions, thinks the latter approach is best. According to her, a specific temperature is less important than keeping your thermostat at a steady, moderate setting rather than making extreme adjustments. “Consistency prevents the AC from overworking while keeping your home comfortable without wasting energy,” she explains. 

The Environmental Protection Agency’s ENERGY STAR program advises upping the thermostat by 7°F when you’re away during the day and even 4°F when you’re asleep, if you can manage it. (They also recommend a programmable thermostat or timer, so the house can start cooling down gradually before you arrive or wake up.)

One thing you should never do, Shaver warns, is immediately crank the thermostat very low to try and cool your home faster. “This wastes energy and can strain the unit,” she explains.

Other energy-friendly tips for staying cool 

There are other things you can do to keep your home comfortable without dialing down the temperature on the thermostat even further. Here’s what Shavers recommends. 

• Schedule routine maintenance, and change your air filters regularly so your cooling system can run more efficiently. (This will also extend its lifespan and reduce energy costs.) 
• Keep blinds and curtains closed during the day to block heat from the sun — ConEdison reports that about 40% of unwanted heat comes through windows!
• Use ceiling or box fans to improve air circulation and help you feel even cooler.
• Avoid using heat-generating appliances like ovens and dryers during the hottest part of the day.
• Make sure doors and windows are properly sealed so that cool air stays inside.
• Keep furniture and rugs away from vents to allow for good airflow, and ensure any outdoor units are clear of debris and plants. 

This article was written by Leslie Corona from Real Simple and was legally licensed through the DiveMarketplace by Industry Dive. Please direct all licensing questions to legal@industrydive.com.