Updated: July 2024

There’s nothing quite like walking inside on a hot and muggy day and feeling that cool relief of an air-conditioned home. By maintaining a much lower temperature in our homes than the temperature outside, our air conditioners are what make the hot summers in the St. Louis area manageable. But how much of a temperature difference can your air conditioner achieve between indoor and outdoor air? Today we’re going to talk about the maximum temperature drop that your air conditioner can handle between indoor and outdoor air and what implications that has on your home’s thermostat settings!

How much can an air conditioner drop the temperature in your home?

Have you ever looked at your thermostat on an extremely hot day and noticed that it’s a few degrees warmer in your home than where your thermostat is set? You might think your air conditioner is just catching up, so you wait a few minutes while your system is running and check your thermostat again. To your surprise, it’s still warmer in your home than it’s supposed to be! Does this mean that your air conditioner isn’t working properly? Not so fast!

When air blows over your air conditioner’s cooling coils, the temperature of the airdrops is about 20 degrees. If your system were to cool down the temperature of your air any lower, the air coming out of your vents would be frigid and uncomfortable. What this means is that your air conditioner supports a maximum temperature drop of about 20 degrees between supply and return air.

On most days, a 20-degree temperature drop is perfectly fine and your home will stay right around the temperature at which you set your thermostat. On extremely hot days, however, your air conditioner might not be able to cool down your home to its normal temperature. If it’s 100 degrees outside, for example, your air conditioner might only be capable of cooling your home down to 80 degrees (although likely a bit lower since your indoor return air is usually cooler than the air outside).

Take an air conditioner’s maximum temperature drop in consideration when setting your thermostat

Now that you know about your air conditioner’s maximum temperature drop, you can use that information to choose the right thermostat setting when it’s extremely hot outside. If you know it’s going to be a very hot day, consider raising your thermostat setting a few degrees to ease the load on your air conditioner. This will help prevent your system from overheating and breaking down on a day when it’s already working overtime.

The worst thing you can do on an extremely hot day is to set your thermostat temperature even lower than usual in an attempt to make your home cooler. All this will do is force your air conditioner to work non-stop and will greatly increase the likelihood of something going wrong.

If you have any questions about the temperature drop your air conditioner can produce, or if you’d like a cooling system serviced or installed in your home, contact Jerry Kelly Heating & Air Conditioning, your St. Louis air conditioning contractor. We provide service all over the St. Louis area, including towns like Maryland Heights, O’Fallon, and St. Charles, MO.

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