Summer has officially arrived with the summer solstice on June 20th.

While it technically wasn't summer by the calendar's standards, Iowa has surely felt the heat of summer for almost all of June. By now, most Iowa homes have used their air conditioner at some point, and if you don't want to throw money down the drain, you should be following the 20-degree rule throughout the summer.

Did you know leaving your AC set to 65, 70, or even 75 degrees might be a complete waste of money, depending on how hot it is outside?

20 Degree Rule

The 20-degree rule is pretty straightforward and can help save you money all summer. What it means is that you should never set the temperature on your thermostat more than 20 degrees cooler than the temperature outside. If it's 100 degrees outside, you should put your thermostat at 80 degrees.

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This may sound like a nightmare to some people, but I've got some bad news for you. According to Frederick Air, most air conditioner systems can't handle more than a 20-degree difference between the outside temperature and the inside temperature.

If it's 100 degrees outside and you have your AC set at 70 degrees, you're going to end up putting more strain on the unit to reach a temperature that it isn't designed to reach. This will cause the unit to run constantly, which will cause unnecessary wear and tear. Not only that, you can watch your bill skyrocket, as your unit can't reach the temperature you're hoping it does.

Logic Behind The Rule

The simple logic behind using the 20-degree rule is based on how an AC unit functions. When an AC unit is running, it not only helps remove heat from the home but also helps remove humidity from your house.

If your unit is asked to cool the air more than 20 degrees below the outside temperature, its ability to do its main two functions diminishes. This will cause extra wear and tear and constant running, which drastically affects your bill every month.

Generally, your AC temperature will be fine when Iowa has temperatures in the 80s. When we hit 90+, you may want to consider adjusting your thermostat. It happens every summer in Iowa and we go on 5-day, 6-day, or week-long stretches of temperatures in the 90s.

If it's going to be 90+ one day and drop down to to the low 80s the next, you're probably fine leaving your temperature for one day but when we go on those long stretches of 90 degrees or more, it would be smart to adjust your thermostat accordingly.

Imagine the AC bill for a house like this! I bet it takes some time to cool down this massive home!