Tuckers Air Conditioning, Heating & Plumbing Blog

The Thermostat and Your Air Conditioner’s Limits


It’s summer planning time, especially with our weather heating up to the point where we’ll need to have air conditioning systems running. Before you let your AC run too much, make sure to schedule regular maintenance service with us. It’s the best job you can have done for your air conditioning in Gaithersburg, MD. You’ll have reliable cooling at lower costs for the summer. 

Right now we want to talk about the thermostat that controls your AC and talk about something that many homeowners don’t know much about: the limits of what their ACs can do.

The Temperature Differential

You may have wondered just how cool your air conditioner can make the house. If your AC is in good working condition and is properly sized for the house, it should rarely have trouble meeting your needs for cooling. But does it have a limit on what it can do?

Yes, it does. It’s the temperature differential, which is how much the AC can change the temperature of the air indoors. When you look at the thermostat, you’ll see it goes down to 60°F (at least on most models). Can you realistically expect to get the house down to that temperature on a hot day? Almost certainly not, because the temperature differential for the standard residential central air conditioner is 20°F. That’s the most the AC can lower the inside temperature compared to the outside temperature. On a standard hot day when it’s 88°F, the lowest temperature the AC can cool the house to is 68°F. If the outdoor temperature is 100°F, the AC won’t be able to lower the indoor temperature to less than 80°F.

Understanding this will help you know how not to push the AC beyond its limits or force it to waste energy trying to reach a temperature it can’t. The bigger the difference between the indoor and outdoor temperatures, the harder the AC will need to run. Not only will it work at maximum power (the 20°F differential), but heat will move into the home faster. 

This is why we recommend raising the thermostat setting as high as you find comfortable during the summer, rather than trying to push it lower to compensate for the heat. We don’t recommend ever setting the thermostat to 60°F during summer: it’s a wasteful setting that the AC probably won’t be able to reach, and it’s too cold for most people anyway.

A recommended summer thermostat setting to help with energy savings is 78°F during the day when people are home. This helps slow down heat gain, and unless the outdoor temperature is above 98°F it will be within the AC’s power to make the house that cool. If it does get hotter, raise the thermostat accordingly—and take extra steps to cool down, like wearing lighter clothes, drinking plenty of liquids, and closing drapes and shutters to keep our radiant heat. At night, raise the thermostat by 8°F. We also recommend this setting for when you’re away: you don’t want to let the house get too hot while you’re gone, because it will take much more energy to cool it down again. 

At Tuckers Air Conditioning, Heating & Plumbing, we vow to exceed expectations at every turn. Schedule your AC services with us.