How Many Air Conditioning Btus Do I Need?

There is a lot of science behind air conditioning.  Determining just how to cool large spaces with a central air system (or alternately, smaller units designed to cool a single room) requires a lot of thought, mathematics, and engineering to ensure that you enjoy optimal temperature control, and that machinery doesn’t get overtaxed and expire before its time.

One of the measurements used to determine the appropriate size of air conditioning unit for your space is the BTU.  What are BTUs, how can they help you determine air conditioner sizing for your needs, and do you need more than one source of AC in your home?  Here are a few things to consider.

What are Air Conditioner BTUs?

BTUs, or British Thermal Units, are a measurement of thermal (heat) energy.  Originally, this method of measurement related to the amount of energy needed to increase the temperature of one pound of water by one degree Fahrenheit (at sea level).  In terms of air conditioning (or alternately, heaters), the listed BTU rating conveys the number of BTUs an AC unit can remove from the air hourly, with 0.24 BTU being the rough standard for changing the temperature of a pound of air by one degree F.

However, it’s not exactly convenient to try to figure out how many pounds of air are in a room, which is why BTU ratings are linked instead to cubic feet.  All you need to know is the approximate square footage of your space so you can compare it to a chart to see the appropriate BTU rating needed to cool your living spaces.

What Air Conditioner Size Do I Need?

You might think that as long as you choose a unit that meets minimum requirements for BTUs, you’re in the clear, but this isn’t necessarily true.  Purchasing a unit too big for your space is just as bad as getting one that’s too small.  A small unit will run constantly without adequately cooling, boosting energy costs and burning out before long.

An overly large unit, on the other hand, will cost more than necessary up front, and it will cycle on and off frequently and for short periods, causing uncomfortable temperature ups and downs and failing to minimize humidity.  So, how can you choose the right size?

The general rule of thumb is to choose a unit at a measurement of roughly 20 BTU per square foot of living space.  Of course, ceiling height could also play a role, which is why cubic measurements are wise, and the number of people sharing the space is also important.  Consider adding about 600 BTU for every person over two that shares living space.

How Many Air Conditioners Do I Need?

If you’re using a central air system for heating and cooling, you should need only a single unit, perhaps with appropriate dampers and zoning to direct the cool air where you need it most.  If you add more people to the household or you don’t have central air to begin with, wall and window units are an alternative, and you’ll probably want one for each room that you spend significant time in.

Here at Rowland Air Conditioning, we have years of experience in calculating and installing the proper size air conditioning system for your home. Give us a call for a free estimate of what the possibilities are to make you cool and comfortable.