Why Does Air Conditioner Sizing Matter?

image of question marks depicting why air conditioner size matters

Air conditioners need to work hard to beat the summer heat. Some of the older models are unable to keep up with the load. Once these start to break down frequently, you must consider getting an air conditioner replacement, or else you will suffer under the sun. Perhaps the only problem is in choosing the right air conditioning unit for the upgrade. It is common for homeowners to seek out something like what they already have, but this might not always yield the best results. You should also banish the notion that the biggest cooling unit will deliver the optimum performance. Home air conditioning is far more complicated than these simplifications make it out to be. If you want a more precise selection process, then ask a professional HVAC contractor to help you determine the proper air conditioner sizing to meet your needs.

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The Importance of a Manual J Load Calculation For HVAC Systems

A Manual J Load calculation is an advanced computation of a home’s cooling needs based on multiple factors. It provides more accurate results (cooling load) than simple rules of thumb. It is something that licensed contractors can provide since they have the training to perform it with precision. Due to the complexity, many use advanced software to crunch the numbers and get immediate results. Contractors will make sure that they input the correct numbers for vital measurements such as the floor area, the ceiling height, the window sizes, insulation rating, the air leakage, the number of people in the home, the heat generated by appliances, and many more. All these will make the result more reliable, allowing you to find the right size for your air conditioner.

Indoor Comfort

image of woman feeling comfortable on couch with central air conditioning system

The job of air conditioners is to cool the air and reduce the humidity to increase indoor comfort. These two tasks are equally important, even though cooling tends to get more focus. Air conditioners bring down humidity by cooling the air around the coils and triggering condensation for the moisture present in the immediate environment. Vapor becomes water beads around the coils, which eventually move down to the condensate lines and out of the system.

This process takes time and it cannot be rushed. Oversized cooling units don’t provide enough time for condensation to happen. They cool down the house so fast that they also go back into idle more quickly. Despite the low indoor temperature, people still feel hot and sticky because of the high humidity, affecting indoor air quality. They might try to push the temperature deeper for relief, yet they never feel any better because they are not addressing the root cause of their discomfort. This short-cycling of oversized air conditioning units may even reduce indoor air quality because less airflow is moving through the filters.

On the other hand, using undersized cooling units is not any better. These will not have enough cooling power to counter the sun’s heat, especially during the hottest days of summer. Even in less extreme conditions, it might take these units a long time before they reach the thermostat’s temperature settings. The HVAC system will push itself to attain the target but the stress will result in greater wear and tear than usual. Service life might be shorter than expected. Along the way, the air conditioner may fail frequently and need repairs.

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Air Conditioner Efficiency

efficiency rating depicting energy efficient home cooling system

Air conditioner unit efficiency is an important specification to consider when choosing a new air conditioner. The SEER rating is the number to look for if you want to keep energy consumption down and ensure manageable cooling costs. Just remember that a high SEER rating is not enough. You must also ensure a proper match between the air conditioner size and the house. A mismatch will prevent the unit from achieving its SEER rating in actual use, thus making the number meaningless. The sub-optimal performance results in wasted energy and higher bills. It also means that the system will be working harder than it really should, further increasing wear and tear. If you want the unit to achieve its potential, then you need to take air conditioner sizing seriously.

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Air Conditioner Cost

As we have already shown, incorrectly sized air conditioners will put you at a disadvantage in many ways. Performance and efficiency will not be as high as you would hope. There is also a financial cost to the air conditioner size mismatch. Inefficiencies will push consumption up, and you will pay for all the extra kilowatt-hours. The strain on the system will result in premature component breakdown. You might have to pay for the replacements and repairs. Check your warranty and verify the extent of your coverage. You may also lose a lot of productive hours because of an ineffective AC, and this might affect your income if you are working from home. It is truly wiser to pay for a professional Manual J calculation now than to deal with all these expenses in the future.

The Problem with Oversized Air Conditioners

feeling hot and sticky due to air conditioner short-cycling

Let’s summarize what we have discussed so far. Oversized air conditioners should be avoided because they will overpower the space. They will cool the house down for sure, but far too quickly. There will not be enough time to work on reducing indoor humidity levels, so it may not feel as comfortable as the owners want. What’s more, large air conditioners come with a hefty price tag and HVAC installation costs. There is no need to spend so much on something that you don’t really need, especially if it will bring problems due to the mismatch.

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The Problem with Undersized Air Conditioning Units

Both extremes are bad for homeowners. Just like oversized ACs, undersized units are also undesirable. They will not be able to cool the house down when you need them the most. They will struggle when the mercury rises to its highest levels, which is dangerous of seniors, children, and pets. There is no reason to own an air conditioner if it cannot deliver on its basic task. It will try its best, but it will only stress its components without achieving its goals. You will end up having to pay for costly repairs.



When you are shopping for a new air conditioner replacement, remember that the middle way is often the best path. Do not go too high or too low. The biggest AC won’t provide the stronger performance. It may just overpower your home and make you pay dearly for the mistake. Instead, be mindful of the exact needs of your space. Find a unit that matches its requirements based on scientific computations. Do not leave anything to chance.

Call Hart Home Comfort for Your HVAC Requirements


Hart Home Comfort offers superior HVAC services in Nassau County, Suffolk County, and Queens, New York. We have the best technicians in the industry with years of experience and well-earned certifications. You can count on us to handle any service that you may need for your air conditioner, including proper unit sizing for replacements.

We provide competitive pricing across all services which are backed by a satisfaction guarantee. If you need reliable and affordable cooling solutions, then give us a call today. Let’s schedule an appointment so that we can give you a free in-home estimate. Call Hart Home Comfort today!

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