We're Always Open Call Us Today!

Sizing Your Furnace or Air Conditioner

Sizing your air conditioner is important.

Here’s what you need to know.

A couple times a year we get calls from customers who have had their new furnace installed by another HVAC contractor.

They proceed to tell me that it doesn’t heat their home properly, or that one of the rooms isn’t warm enough.

I always ask if they had a heat calculation done on their home prior to installation, and almost always they answer,

“I don’t know what that is.”

Make sure that when you have a HVAC company give you a free estimate on a new furnace or air conditioner they do a heat gain or heat loss calculation.

It’s common practice, and unacceptable if they don’t use a furnace size calculator to determine the right furnace or AC unit for you.

What is a heat calculation?

A furnace size calculator is used to perform a heat calculation to determine how much heating or cooling your house needs, using BTU’s (British Thermal Units).

A few factors are required for this calculation, including:

  • Size of your home
  • Insulation
  • How many floors you have
  • Windows
  • The duct runs

Why is a heat calculation so important?

The size of your furnace or air conditioner plays a large role in efficiency, directly impacting your monthly energy costs, so using a furnace size calculator is essential.

Here’s why:

  • If a furnace is too small for your home, it will have to work extra hard in order to bring your home to the proper temperature, compromising its efficiency
  • If a furnace is too large, it will heat your home too quickly, cycling on and off constantly, thus driving your efficiency down as well

Ask the HVAC Company who is visiting your home to provide you with details of their heat calculation. If they haven’t made one, be sure to ask them which furnace size calculator they used to determine the right size system.


You don’t need to worry about the sizing of your HVAC equipment too much as Metro Heating and Cooling will use a furnace size calculator to perform a heat calculation for you.

We’ll determine the exact size furnace or air conditioner you need to keep your home hot or cold as required.

Contact Us at (651) 294-7798 to tell us what you need.

Schedule a HVAC repair anywhere in the Minneapolis or St. Paul area today by calling (651) 294-7798 or by requesting an estimate online.


Contact Us

1220 Cope Avenue East, Maplewood, MN 55109