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What Size Air Conditioner Do I Need for My House?

What Size Air Conditioner Do I Need for My House?

Air conditioners are measured in tons. The bigger the size (1-ton, 2-ton, etc.), the more heat it can remove from your home. 

And the size you need depends on many different factors. To ensure that you’re getting the perfect size for your home, you need to hire a professional technician to perform a “heat-load calculation”.

What is a heat-load calculation?

Heat-load calculations involve a complete home inspection and software calculation by a professional technician. The results determine how much cooling a house truly needs every hour and breaks the cooling needs down room-by-room.

Load calculations focus on a long list of variables such as your home’s:

  • Geographical location 
  • Height of ceilings
  • Number of windows
  • Type of windows
  • Insulation level
  • Number of people


Manual J load calculations are approved by the Air Conditioning Contractors of America (ACCA) and offer accurate AC system sizing. Photo Courtesy of Energy Vanguard

Caution: Lazy technicians = improperly-sized AC’s

Because heat-load calculations take time and attention to detail, many technicians skip it and use rules of thumb to determine your AC size. 

However, a technician who doesn’t perform a heat-load calculation is more likely to suggest the wrong size air conditioner.

Now you may be thinking, “is an incorrectly sized AC really all that bad?

Yes. 

Buying an AC that is too small for your house means that it has to work harder than it was designed to without ever cooling your home off.

If you buy an AC that is too big for your house, it will cool your house too quickly and cycle on/off much more than it should. 

Both situations lead to inefficient cooling, higher energy bills, and system damage.

To avoid getting stuck with the wrong size, be on the lookout for technicians who base the size of your new air conditioner only on the square footage of your house. Yes, this is one of the factors you should consider when choosing your AC size, but it shouldn’t be the only one. 

A house with a smaller square footage may require a bigger AC system than a larger house if the smaller house has worse insulation, bigger windows, higher ceilings, more windows, etc.

This video does a good job of explaining why square footage can’t be the only basis for your home’s air conditioner size.

Another lazy rule of thumb that some air conditioning companies use is to just give you the same size AC as your old system. This could leave you with the wrong size AC because

  • Your old air conditioner may be sized incorrectly
  • You or a previous owner may have updated your home (with newer insulation, better windows, etc.)

Find the right AC size for your house

If you’re in the Minneapolis or Saint Paul area, MSP can help you determine the correct AC size needed for your home. Our technicians always perform thorough heat-load calculations.

Get started with a free quote.

Further reading:

Categories: Air Conditioning