It will make a huge difference indoors when you need it the most.
During the Southern summers (and heatwaves that follow), we're always looking to our AC unit to work overtime. But if your home isn't feeling as cool as it should, you may need to try the 20-degree rule. This common HVAC trick is often misunderstood, but when it's done right, can make your home feel completely cooler and more comfortable on the hottest days. To make sure the confusion was behind us once and for all, we spoke to two professional HVAC experts for everything you need to know about using the 20-degree rule properly in your home this summer.
Meet the Experts
- Pete Green is the owner and founder of Go Green Plumbing, Heating, Air, & Electrical in Greensboro, North Carolina.
- Robert Dykes is the general manager of A1 Plus Electrical, Plumbing, and Air in Houston, Texas.
What Is The 20-Degree Rule?
Basically, the 20-degree rule refers to the amount of heat your AC unit removes from the inside of your home. This rule gets its name from the fact that it's designed to produce a 20-degree difference from the air that's going in the intake to the air that's coming out. What's good about this rule is that Robert Dykes, an HVAC expert in Houston, says a properly running system is designed to do this effectively.
"In other words, if it is a scorching 100°F day outside, a perfectly tuned, efficient AC system is realistically only going to cool the indoor temperature to about 80°F," he says.
How Does It Impact Your AC's Lifespan?
Not only does this rule make your home feel much more comfortable, but it also protects the longevity and efficiency of your central cooling system. The mistake that many homeowners make, according to Dykes, is that they set the gap between the outside and inside temperatures too far, like setting the thermostat to 70 on a 100-degree day.
"This takes a toll on your system," Dykes says. "Your unit won't cool the house faster or make it cooler. It will just run continuously without ever reaching the target temperature. This leads to short-cycling (turning on and off rapidly) or constant running, which can overheat the compressor, increase energy bills, and shorten the unit's overall lifespan."
Where the 20-degree rule helps with this is that it doesn't provide a gap that's too big for the system to handle. Instead, your unit doesn't have to work as hard to reach your set temperature, which means there isn't as much strain on put on your system that can affect its performance.
Other Factors That Affect Air Conditioner Performance
While a large gap can certainly take its toll on your unit, there are other factors that can play into how well your AC unit cools your home. One example is not setting consistent temperatures. HVAC expert Pete Green says keeping it set at a consistent temperature doesn't make your unit run as hard.
"If you are trying to change our system by 5 degrees, like from 75 degrees to 69 degrees, you're making your system work a little harder than it should. So if you keep your home at the same temperature, it typically doesn't have to work as hard," he says.
Along with this, there are a few other ways you can preserve the lifespan of your AC unit by controlling a few things indoors:
- Closing your curtains: According to Dykes, 30% of home heat comes from radiant heat through windows. He says using dark curtains or heavy blinds during peak sun hours can significantly reduce the thermal load on your AC unit.
- Using your ceiling fan: "Set ceiling fans to run counter-clockwise. But fans don't cool the room, they cool people by cooling the skin, which makes a room feel 4°F cooler than it actually is," says Dykes.
- Pre-cool the home: Dykes says, "If you know a heatwave is coming, you can pre-cool the home by lowering the thermostat a few degrees before the sun peaks in the early morning. It is easier for your AC to maintain a cool temperature than to recover from a hot house."
- Provide airflow: "One of the easiest things to do is to change air filters monthly during peak summer season. Clogged filters restrict airflow, forcing the blower motor to work harder and even causing the evaporator coils to freeze in some cases," says Dykes.