10 Air Conditioning Mistakes You Can’t Afford to Make

Updated: Dec. 17, 2023

Ignoring proper air conditioning management raises your energy bills, decreases the efficiency of your system and ultimately requires repairs. Avoid these 10 common mistakes and reap the cool rewards!

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air conditioner with landscaping
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Ignoring Sizing Requirements

HVAC pros carefully size air conditioning units to match the number of cubic feet in a new building. When purchasing a new AC unit or renovating your house, the homeowner must make sure the unit fits the space properly.

Installing an air conditioning unit rated for a smaller space than your home causes it to work overtime cooling the air. Overworked air conditioners wear out more quickly and struggle to meet the demands of the thermostat. An air conditioning unit rated for a larger space than you have constantly turns on and off, wearing itself out and growing undependable over time.

Pay attention to capacity and pick the right unit for the space you have. Ignoring these nine air conditioner myths pays dividends over time.

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vacuum air conditioner
Family Handyman

Never Cleaning Fins and Coils

Air conditioner coils and fins help the evaporators inside the house and the condensers outside absorb and release heat. This process of moving heat is vital, but layers of dust and grime impede it. If you never check your coils, that grime decreases efficiency and costs you money. Clean your air conditioner at the beginning of the warm season and check it from time to time, particularly after storms or high winds to make sure your coils and fins stay clear.

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Ignoring Your Air Filter

Your home’s air filter removes dust, allergens and more from the air passing through the system. You must replace these lightweight cardboard-and-wire constructs regularly. After six months or so, that filter becomes so choked with dirt that air has a tough time getting through, and the unit can’t really do its job anymore. That not only increases the dust in your home, it greatly decreases airflow for your air conditioning unit.

You can improve energy use for your air conditioner by five to 15 percent just by replacing a dirty filter. So make sure you install a new filter a couple of times a year. And remember to check and change it after particularly dusty activities, like cleaning ductwork, a big demolition or refinishing a wood floor.

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Not Updating (or Setting) Your Thermostat

In today’s technology climate, you may regard programmable thermostats with a yawn, but that doesn’t mean you shouldn’t have one. Programmable thermostats let you set temperatures for various times throughout the day, saving you money and managing your cooling without constant attention. Many advanced thermostats like Google’s Nest thermostat can learn your home’s rhythms, so the thermostat can shift to accommodate repeated schedules. It also allows you to change the temperature from an app.

If you lack one of these programmable or smart thermostats, the time to upgrade is now. Save money and enjoy more accurate cooling with a thermostat replacement, particularly if your current thermostat lags a couple of decades behind the times. Find out if it is cheaper to leave the air conditioner on all day.

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Not Checking Your Drain

Not Checking Your Drain

Many air conditioning systems use drains that collect condensation and prevent moisture issues by channeling water outside of the house. These drains can be easy to miss, but they have an important job. A clogged and overflowing drain creates bad news for your air conditioning system and even worse news for surrounding floors and walls, which can sustain permanent damage. So keep your drain line clean, and consider snaking it with a wire every year or two so gunk doesn’t accumulate.

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Setting the Temperature Too Low

This common mistake goes back decades, when many homeowners didn’t understand how air conditioning systems worked. People frequently turned their thermostats way down, thinking it would cool the space faster. It doesn’t.

Air conditioners run at full power or turn off. Thus they work just as hard to lower the temperature one degree as they do to lower it by 20 degrees. Larger changes just cause it to run longer. So program your thermostat to exactly where you want it, not lower than you need.

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fix air conditioner
JP WALLET/Shutterstock

Avoiding Replacement

The initial cost of replacing your air conditioning unit is high, but that doesn’t mean you should avoid a new purchase. Don’t make the mistake of keeping your old air conditioner long after you should. If you’re planning to buy a new one, you must check out this environmentally sustainable moss air conditioner.

Older air conditioners that perform poorly cost you more in repairs and run less efficiently than new models, even when they were new themselves. By replacing air conditioning units aged 10 to 12 years or more, you could start saving money on monthly bills by investing in a newer, more efficient version. Plus: These simple tricks will keep your house cool all summer long.

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Never Arranging a Check-Up
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Never Arranging a Check-Up

As we mentioned, most air conditioning systems use refrigerant that absorbs heat from the house and disperses it outdoors. This refrigerant compound is important to air conditioner operation, but small amounts can escape over time, making the system less efficient. How do you know if you need to add refrigerant? Arrange for an experienced technician to test your air conditioning system and top off your refrigerant, if needed.

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Using the AC When No One Is Home

Using the AC When No One is Home

When setting schedules, pay attention to when the house actually has people in it. During the week when your family is away at work or school, turn the temperature up significantly to save money. Don’t set the air conditioning to lower the temperature when no one benefits from it.

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Forgetting About Your Windows
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Forgetting About Your Windows

A lot of heat enters the home through windows, especially open windows. If you really want to control heat in your house, pay attention to your windows, too. Keep them closed with blinds or drapes drawn during the hottest parts of the day, particularly windows facing the sun. In the evening, open upstairs and downstairs windows to encourage the natural flow of cooler air. The less work an air conditioner has to do, the better! Plus: 12 aha! ideas for keeping your house cool this season.