Why Does Air Conditioner Sizing Matter?

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The summer season can push cooling systems to their limits. Oftentimes, it becomes clear that an older AC unit cannot handle the high temperatures. If an air conditioner begins breaking down often, it’s time for a replacement. It can be hard to choose what type of air conditioner will work best. It’s tempting to get a similar model to your old one, but this could cause a similar mistake to happen in the future. It also might be tempting to get the biggest air conditioner, thinking it will cool down your house quickly. But, the best way to go about choosing a new air conditioner is to start fresh and rethink the needs of your house. One key factor of any new AC installation is air conditioner sizing.

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What Is A Manual J Load Calculation & Why Is It Important?

A Manual J load calculation looks at several influences to determine the cooling needs of a home. Licensed contractors will perform this calculation to understand what size of air conditioner your home needs to efficient cooling. Some contractors will even use advanced software to help with the precision of the calculation. It’s important to know many aspects of the house like the floor area, orientation, window sizes, ceiling height, building materials, heat generation of household appliances, window sizes, local climate, air leakage, and the number of occupants. This calculation shows the cooling load of the home. There is no guessing needed with the numerical value from the calculation. It will tell you how big or small of an AC unit you need.


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Air conditioners make your home feel more comfortable. Besides just cooling, ACs also reduce humidity with condensation. Vapor around the coils turns into water beads that run through the channels. Oversized units cool the house down so quickly that the cycle will end before condensation even occurs. There will still be humidity in the house which makes it feel uncomfortable and sticky. When this happens, people lower the temperature which uses more energy. Oversized units have shorter cycles which reduces indoor air quality. Less air goes into the filters, which in turn reduces the cleaning process.

Oversized units aren’t the only problem, undersized units have issues too. They can’t keep up with the home’s cooling needs, so it takes a long time before they can reach the wanted temperature. On some hot summer days, an undersized unit will have a hard time offsetting the sun radiating on your roof. They end up working harder but still falling short. Undersized ACs run constantly which means wear and tear will occur faster. Early replacements and frequent breakdowns are very common.

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A unit with a high SEER rating guarantees effective cooling power. Homeowners should consider other factors like sizing. Units with the wrong sizing will run sub-optimally with very short or long cycles. This causes lots of energy waste. Wear and tear limits the unit from running efficiently. Buying a new AC with a high SEER rating is pointless if it is not sized correctly.


A mismatched unit will end up costing a lot of money since you’ll end up spending more on your cooling system. The price of units increases with more horsepower so it’s important to consider your home’s cooling needs prior to choosing a unit. Energy is wasted with frequent cycling and it leads to high monthly bills. The stress on the parts can lead to many repairs and replacements. To avoid unneeded expenses, make sure you go through the process of proper sizing. Having a professional perform a Manual J calculation is a great approach.

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The Problem With Oversized AC Units

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In summary, oversized units cool spaces too quickly and lead to short cycles. This is problematic because it prevents effective lowering of humidity and there are no improvements in air quality. These issues cause an increase in energy consumption and your home will feel cool but humid.

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The Problem With Undersized Air Conditioning Units

Undersized units are just as troublesome as oversized units. They do not have enough cooling power to cool off a space. Furthermore, they won’t bring relief from the heat you need in the summer. They run constantly and fail to reach the chosen temperature. Components are always stressed and this leads to equipment failures and early replacements.



Air conditioner selection can be a complicated project. A smaller or bigger unit doesn’t guarantee good performance. Spaces have different needs, so not one size will work for every space. The right unit meets the unique sizing requirements. Sizing is very important when choosing a unit because it determines efficiency, cost, and comfort. To ensure you get the correct size, it’s essential to work with a licensed contractor who can calculate the perfect size for your space.

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Call McAllister Energy For Your Air Conditioning Requirements

McAllister EnergyMcAllister Energy offers superior heating and cooling services all throughout Camden County, New Jersey. We hire the best certified technicians who can provide you with excellent HVAC tune-ups, repairs, installations, and replacements. Each of our techs has the knowledge and experience to service your HVAC system correctly.

McAllister Energy guarantees the most competitive heating and cooling service costs in the area. Our maintenance services can improve your comfort, increase your energy efficiency while reducing your home cooling costs. If you happen to need an HVAC repair or replacement system, we can recommend the best one for your home while staying within your budget. We back all of our work with a guarantee to ensure your satisfaction. To schedule a service appointment, give McAllister Energy a call today. We offer free, in-home estimates.

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