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If you’re in the market for a new air conditioner, you’ll have a lot to consider. What features do you want? How efficient do you want it? How much do you want to pay for your new system? Do you want a central air conditioning system or a single-room system like a mini-split? While each of these questions is important, arguably the most important question to ask is what size air conditioner you should purchase. Purchasing an air conditioner that’s too large or too small for your purposes could lead to a lot of undesirable results, including actually costing you far more in the long run.

A/C Sizing Explained

Air conditioners are sized by the amount of air they can circulate over a period of time, generally measured in the form of “tons.” Contrary to what this might sound like, a “ton” in air conditioner capacity is not a unit of weight, but a unit of mass. A one-ton air conditioner can cool 12,000 British Thermal Units (BTUs) in one hour. A British Thermal Unit is the amount of energy required in order to change the temperature of one pound of water by one degree Fahrenheit.

For the average home, you’ll generally need anywhere between 1.5 tons and 5 tons of air conditioning capacity. Generally, anything over 5 tons is considered to be a commercial-grade air conditioner and isn’t suitable for your home. Don’t let anyone try to convince you otherwise: an HVAC company that simply tries to tell you the biggest air conditioner possible in order to make the most money doesn’t actually care about the outcome or your satisfaction. Why not? Let us explain

What Happens When Your A/C is Too Big?

When your air conditioner is too big for the space it’s cooling, lots of things can happen. For starters, a system that’s too big increases the air pressure throughout your duct system and in your home. When this air pressure difference is present, you’ll notice it’ll be hard to open the doors outside (especially on windy days), and you may even notice that going outside feels just a touch lighter, almost as though a small weight has been lifted off of your body. Finally, the air pressure difference can and will wear out the weather stripping and seals that are designed to keep the treated air in your home and untreated air outside where it belongs, leading to unwanted heat loss or gain.

There’s another problem with large air conditioners, however. An A/C that’s too big won’t cool your home efficiently, contrary to what you might think. Logic dictates that a system that has a much higher air throughput will force more cool air into your home and thus cool your home faster, meaning it needs to be run less often. However, this isn’t usually the case. Slow and steady is actually the most efficient way to cool your home in that modern air conditioners are designed to cool your home gradually while running for a longer period of time.

A system that’s too large will start “short cycling,” in other words rapidly turning on and off every few minutes. This usually results in significantly higher heating and cooling bills because systems burn the most energy when they’re turning on and getting up to speed. When systems are running smoothly, they actually burn very little energy compared to the startup process. A system that’s constantly turning on and off from short cycling will just drain energy, sapping money from your wallet and even shortening its own lifespan from the added wear and tear it will sustain.

What Happens When Your System is Too Small?

A system that’s too small isn’t as bad as a system that’s too large, but it’s still not necessarily a good thing. To put it simply, a system that’s too small will run constantly and struggle to keep up with the demand you’re throwing at it.

Unlike the systems from before which drained a ton of energy trying to cool your home rapidly, today’s systems are designed to keep you cool by working to evenly cool your entire home to one target temperature. A system that’s too small may make one room feel nice and comfortable, but the rest of your house will continue to be too warm. When the cool air from the treated room dissipates and spreads to the remaining rooms, it’ll be replaced by warm air again, which means the system will turn right back on, and the process just starts over again. As a result, your system runs far too long and too often, and you burn a ton of energy, which only costs you a ton of extra cash.

It’s strongly advised you seek the assistance of a Sterling air conditioning expert in order to determine the right size air conditioner for your home. Contact Donmar Heating, Cooling & Plumbing today at (703) 457-8676 to request a case evaluation!

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