Q - I am in the process of buying a new air conditioner. My current system is a 3 ton unit and it seems to run a long time to cool the house when it is especially hot outside.

Would getting a bigger unit, i.e. more tonnage be a more practical option?

Steve in Decatur

A - One would think so. A larger unit would produce more cool air faster thus shortening the run time of the unit and saving you money on your energy bill.

However one would be wrong.

While a larger unit would kick out more cool air over a shorter run time that would not really be good for your house.

The main function of your a/c unit is to reduce the amount of humidity in your home which makes it much more comfortable to live in. Shortening its run time will not remove enough humidity to make your house comfortable.

In fact, it will be just the opposite. Your house will feel cool, but it will be a clammy and yuck feeling. Ever been in a cave? That would be your home.

So when your hvac company comes out to size your house for the correct size unit (and every new install should come with an hvac company coming to your home to do a size calculation) you should get the correct size unit to keep your house cool and your humidity levels low.

Also, as a quick note - your system will run for a long time when it is 95 degrees outside and your thermostat is set for 78 degrees. Figure your a/c can only cool the outside air by about 17 degrees and you will see the work it is doing.