Is Your Air Conditioner Underperforming?

There are many reasons why your air conditioner may be underperforming. Your system could be low on refrigerant, your evaporator coil could be clogged, the filter could be dirty, or the air ducts that lead to each room in your house could be damaged or crushed. These problems can lead you to think your AC is undersized, and you should get a bigger air conditioner. Today I want to tell you why getting a bigger AC may not be the best idea.

The Owner’s Hunch

As the Chicagoland area grows outward, new neighborhoods have sprouted up very quickly. After the haste, many folks I’ve talked to have complained that their air conditioner seems to be undersized. And sometimes they are right!  Sometimes the HVAC contractor that installed that system didn’t consider that the house has 10-foot ceilings instead of the usual 8-foot ceilings.

Doing the Math

That isn’t the only thing we look at either. In both older and newer homes, the square footage of the house is important. The type of windows and doors, the orientation of the house, as well as the impact of any trees that might be covering the house are all also important.  And the insulation levels in the house are also important. All of these factors are used to figure out the proper size for a home’s AC unit.

Summer Heat

If your home’s air conditioner is undersized, you’ll know it because it will just run, and run, and run, even on 80- and 95-degree days. That’s warm, but nothing compared to some of the hotter weeks of the high 90’s! Most air conditioners these days are designed to be efficient to 95 degrees or less.  Anything hotter than that, and EVERYONE’S air conditioner is going to run non-stop.

Going Bigger

This is typical for a lot of the homes around the Chicagoland area. But some people wonder if a bigger sized system is a good idea. Here are some factors I would consider when considering the move to a bigger system:

Your air ducts are sized for the sized system you have now. If you get a bigger system you can really affect the static pressure of the system. Static pressure is like the blood pressure in your body. If your heart was too big for your body, it could cause complications with your blood pressure, right?  Well it’s the same with the static pressure of your HVAC system. The bigger air conditioner and its compressor won’t be able to operate under the same comfortable conditions as it would if it was properly sized. This will lead to early system failures of your new HVAC system.


A bigger system is also not going to feel as comfortable for your house. Humidity isn’t as big a deal out here in California, but in other areas of the country it is. Either way, the comfortability factor is compromised when you get a bigger system.

Imagine this. When you turn on the AC in your car on a hot day, the air comes on full blast until you start to feel nice and cold in there. Now, turn that AC back off, and it starts to feel muggy and strangely warm too quickly. The car walls, seats, leather and other things in the car haven’t gotten cool yet. That’s the same thing you’ll experience in a house with too big of a system.

The thermostat might satisfy at the temperature you’re asking for more quickly, but it kicks right back on quickly too. This can really mess with the humidity levels in your home because the system hasn’t run long enough for it to do its job, which is to cool your house AND dehumidify the house at the same time. Ideal humidity levels in our homes here are around 45-55%. Anything more than that and it really starts to feel sticky in there.

Wear and Tear

Another reason to size it right is because now that your larger system is constantly turning on and off all day on these hotter days, the motors will wear out faster. The most damaging time for a motor, especially your $2000 compressor, is when all that damaging heat and energy slam into that motor to get it running. Yes, it levels off once it’s running but the starting and stopping is what really hurts those expensive motors.

The right sized system runs for longer times but cools your house more effectively by getting your walls, your furniture, the carpet and ceilings cool as well as the occupants in the house. That’s why getting it right is so important.

In Summary

Getting a larger AC than you need might sound appealing, but it’s torture on your new system. It probably won’t last as long as it’s supposed to, and you’ll be buying a new system sooner than you should.

I hope this blog post has helped you understand the importance of not getting an oversized air conditioner for your home.