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Premier Heating & Air Blog

Why an Oversized AC Is a Truly “Big” Problem


In a recent post, we debunked several common myths about air conditioning systems. We didn’t have space for all the major misconceptions people have about ACs (there are plenty!), but we wanted to write a specific blog post about one we didn’t include because it deserves special attention. This is the myth that “There’s no such thing as an air conditioner that’s too powerful.” Or, in HVAC terms, “an oversized AC.”

When people are looking for a new air conditioning installation in Conyers, GA, they often fall into the mistaken belief that it’s better to err on the side of an AC that’s too powerful rather than one that’s not powerful enough. It’s easy to see why this is a common belief. If the AC provides too much cooling, you can just adjust the thermostat, right? 

However, the sizing of an air conditioning system for a house is complex, and both undersized and oversized ACs create problems. An undersized AC won’t be able to cool the house fully, and an oversized AC will … well, we’ll get into that below.

An Oversized AC Will Short-Cycle

The main trouble with a central air conditioning system that is too powerful is that it will start to short-cycle.

Short-cycling is a common AC fault that can occur for a number of reasons. When an AC short-cycles, it fails to complete a regular cooling cycle and instead shuts down early, only to restart the cycle a short time later and repeat the process. The AC will become stuck in a rapid on/off repetition, with cycles lasting less than 10 minutes. (Normal cooling cycles last 15–20 minutes.)

The reason an oversized air conditioner will short-cycle is that it pushes out cool air in such high volume that the HVAC system will mistakenly believe it has finished cooling the house. The thermostat near the center of the home will signal to terminate the cycle early. This can’t be overcome by lowering the thermostat, as this will just cause the air conditioner to run less and leave the house too hot. The AC’s cooling output has to match the house—this is why professional sizing is critical.

The Trouble With Short-Cycling

You don’t want your AC to short-cycle for any reason because it puts enormous strain on its components. It’s not good for any powerful mechanical device to start and stop rapidly. A short-cycling AC will wear down quickly and need extra repairs or an early replacement.

On top of these problems, short cycling drains large amounts of power. An air conditioner uses the most electricity at start-up. So if your AC is short-cycling, you can expect to see extremely high electric bills.

Finally, short-cycling won’t allow an air conditioner to remain on long enough to evenly distribute cooling to the house. Many rooms will remain too warm.

The best way to avoid an oversized AC is to always rely on professionals like us to handle an air conditioner installation. We use extensive calculations to determine the correct size for an AC we install.

Experience the Premier Difference! Premier Heating & Air has been family-owned and operated since 2001.

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