Air Conditioning June 23, 2026

What To Set My Thermostat to When It Is Hot

As summer temperatures rise, we all know how important air conditioning can be to our comfort. Many of us are tempted to crank down the thermostat to escape the summer heat. However, is there such a thing as too low of a thermostat temperature in the summer?

Our experts share the ideal temperature to set your thermostat to in hot weather, to maximize both comfort and efficiency.

Quick Summary

Northern Virginia summers regularly bring temperatures into the high 80s and 90s, and knowing how to set your thermostat correctly makes a real difference in both comfort and your energy bill. Here is what this article covers:

• The U.S. Department of Energy’s recommended summer thermostat setting and why it works
• A quick-reference temperature table matching outdoor heat to ideal indoor settings
• How to adjust your thermostat for when you are home, away, and sleeping
• The 20-degree rule and why going below it strains your AC
• Bonus tips for staying cool during Northern Virginia heat waves

If your AC is struggling to maintain comfortable temperatures no matter what you set the thermostat to, that is a system problem rather than a settings problem. Parrish Services provides AC repair and maintenance services across Northern Virginia to keep your system ready for the hottest days of the year.

What is the Best Thermostat Setting for Summer?

The U.S. Department of Energy recommends keeping your home at 78° Fahrenheit when you’re home and awake during the summer months. This temperature strikes a good balance between staying comfortable while limiting strain on your AC unit.

Of course, “comfortable” is subjective and varies from person to person. If 78° feels too warm for your preference, you can lower it a couple of degrees.

Just remember, every degree you raise the thermostat over 72° can save you up to 3% on cooling costs in hot weather.

Outdoor Temperature vs. Recommended Thermostat Setting

For a quick rule of thumb, follow our guidance below on what temperature you should set your thermostat based on the outdoor temperature:

Everyone has different comfort preferences and every home is built differently, so these are not hard and fast rules that you have to follow. Find the ideal thermostat setting for your home that allows you to maintain your comfort. Additionally, your AC’s ability to reach a given indoor temperature depends on the system’s size, age, condition, and the home’s insulation. If your system cannot maintain the recommended setting during a heat wave, a maintenance visit or AC repair may be needed.

Recommended Daily Thermostat Schedule

To maximize comfort and efficiency even more than the suggested 78°, you can change your thermostat settings throughout the day based on your routine. Programmable or smart thermostats can help make this even easier, too.

Thermostat Temperatures for When You’re Home and Awake

• 76°-78° is ideal during the day if you are home. This will keep you comfortable but still stay efficient and prevent your AC from running in too long of cycles.
• Use ceiling fans to help circulate the air and add a breeze to make it feel cooler.
• Avoid setting the thermostat too low. If it is 95° degrees out, even if you set your thermostat to 68° degrees, your AC will most likely not be able to reach this temperature and will just use more energy.

Settings for When You’re Away from Home:

• Raise your thermostat up a few degrees when you leave the house. This will reduce strain on your AC and limit energy consumption when you don’t need it.
• Setting your thermostat between 80°-85° when you’re away during the day or on vacation can boost energy savings.
• If you have pets that stay at home, we recommend keeping your thermostat between 78° and 80° so your furry friends can still stay safe and comfortable.

Best Temperatures for When You’re Sleeping:

• Most people sleep better when it’s cooler. In hot temps, the best thermostat setting at night is between 72°-75°.
• Try to use natural cooling, like opening windows and using fans. The outside temperature naturally gets cooler at night, so take advantage of the cooler hours.

The “20 Degree Rule”

We all have different preferences for the temperature we like our thermostat to be set at. Some people might think 78° is way too hot for their liking—and that’s okay!

When cooling your home, there is a general rule that you shouldn’t set your thermostat lower than 20 degrees below the outdoor temperature. For example, when it is 95° outside, you should set your thermostat to 75 degrees or above. Or, if it is 88 degrees, try to keep your thermostat set to 68° or above.

More than a 20° difference will strain your AC, increase energy costs, and possibly cause breakdowns or unwanted repairs. If you still think it is too warm, try some of the natural cooling suggestions below and take advantage of cooler temperatures at night.

Bonus Tips for Air Conditioning in a Heat Wave

Whether you live in Manassas, Gainesville, Centreville, Woodbrige, Haymarket, or the surrounding areas, Northern Virginia summers can get hot and muggy, with heat index values that regularly push into triple digits through July and August. That means your AC must work harder to maintain comfort during the peak of the season. If your home gets particularly warm or humid, try these tips for staying cool:

• Don’t set the thermostat too low, too fast: Dropping it to 65°F won’t cool your home faster; it will just keep your system running longer.
• Consider using a dehumidifier: Humidity control removes excess moisture and improves comfort at higher thermostat settings.
• Use a programmable or smart thermostat: Set schedules for when you are home, away, or sleeping to avoid unnecessary energy use.
• Keep doors and windows closed: Especially during the hottest part of the day, keep your cool air inside where it belongs.
• Close curtains and blinds: Sunlight streaming through windows can raise indoor temps fast. Use window coverings to reduce heat gain, especially on south-facing windows.
• Use ceiling, floor and window fans: Turning on your fans during the day can help you feel cooler by keeping air flowing. At night, try opening your windows if its cooler, and draw cool air in with window fans.

Keep Your AC Efficient with Parrish

The best way to keep your home comfortable all year round is to get regular air conditioning maintenance. Our professional HVAC technicians at Parrish can perform annual heating and cooling maintenance, as well as help you with emergency repairs when you need them most. Don’t hesitate to book your AC repair or replacement before the next heat wave.

The best way to keep your home comfortable all summer in Manassas, Gainesville, Centreville, Woodbridge, and across Northern Virginia is to keep your air conditioning system in top shape. Parrish Services offers HVAC maintenance, AC repairs, and AC replacements to ensure you have reliable cooling. If humidity is making your home feel warmer than the thermostat suggests, our whole-home dehumidifiers can help significantly. And if you are still adjusting your thermostat manually, upgrading to a Wi-Fi smart thermostat lets you set schedules and control your home’s temperature from your phone

Stay comfortable during a Northern Virginia summer with the help of Parrish Services. Contact our team today to schedule an appointment for air conditioning services in Manassas or the surrounding areas.

Frequently Asked Questions

What is the lowest you should set your thermostat to in summer?

Most homeowners are comfortable setting their thermostat between 72°F and 78°F during the summer, depending on personal preference and whether anyone in the home has specific comfort or health needs. Setting it much lower can increase energy use without providing additional benefits, especially if your AC system is already operating properly. You also should not set your thermostat to more than 20 degrees lower than the outdoor temperature.

Does setting the thermostat lower cool my home faster?

No. Your air conditioner cools at the same rate regardless of how low you set the thermostat. Lowering the temperature well below your desired setting won’t speed up the cooling process. Instead, try lowering your thermostat gradually, adjusting only by one to two degrees at a time.

When should I call Parrish for AC service instead of adjusting the thermostat?

If your home never reaches the temperature you’ve set, your AC runs constantly, blows warm air, or cycles on and off frequently, the issue may be with the HVAC system rather than the thermostat settings. Our experienced technicians at Parrish Services can inspect your air conditioner, identify the underlying problem, and recommend the right repair or maintenance to restore reliable cooling.