Getting a new AC unit? Bigger is better.  Right? Not always.  Purchasing the right size AC unit for your home will balance keeping your home cool and energy efficient.  Heating and cooling our homes can account for nearly half of our power bill each month. Electricity is expensive. You don’t want to waste it on running a unit that is too big. On the other hand, getting an undersized unit will not keep your house cool. When we talk about “size”, we are talking about capacity to cool, not physical size.

How big does your new AC unit need to be?

So, how much capacity do you need for your home?  You can perform a crude estimate. An air conditioner unit’s capacity to cool is measured in tonnage as well as BTU (British Thermal Unit) per hour.  One ton is equal to 12,000 BTUs per hour. Here in Florida, you will generally need 1 ton for every 450 – 600 square feet of conditioned space. However, this is only an estimate.  There are many other factors to consider to accurately calculate the correct capacity needed for your home.

Factors to consider for a new AC

These factors include how many people live in your home, heat transfer between walls, number of windows – type and direction they face, insulation type and R-value, ceiling height, presence of sunlight or natural shade, number of heat generating appliances, et cetera.  To make a wise investment in a new AC unit, there really is no substitute for using a reputable HVAC company that can accurately determine your needs.

Why not err on the side of caution and get an AC unit that is larger than recommended for my home?  The larger the unit, the higher the upfront cost. Air conditioners use a LOT of electricity. A larger than needed unit will result in higher monthly power bills than a properly sized unit.  An oversized unit will cycle on and off many times throughout the day and won’t get rid of humidity as well as a properly sized unit. This quick cycling also results in more wear and tear. An oversized AC unit does not cool as evenly as a properly sized unit.

What if you save a little money upfront and purchase a unit that just doesn’t have enough capacity to get the job done?  You guessed it. It will not keep your house at a comfortably cool temperature on the hottest days. While a larger unit uses lots of energy, an undersized unit will run almost constantly during the summer and will also result in higher bills than a properly sized unit.

If you need a new AC unit for your home, your best course of action is to use a reputable HVAC installer that can accurately calculate the size unit you need for your home.  Many units fail before they should because of improper installation. Don’t invest a significant sum in a great AC unit with a good warranty and try to save a few dollars hiring a terrible installer.

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