What Size Heat Pump Do I Need? A Plain-English Guide

Heat pumps are sized in tons, and one ton equals 12,000 BTUs per hour of heating or cooling. Get the size wrong and you pay for it every month.

Why size matters

• Too big and it short cycles, wears out faster, and leaves the house clammy in summer.
• Too small and it runs nonstop and leans on expensive backup heat when it's cold.

Why square footage rules fail

You'll see rules like one ton per 500 to 600 square feet. They're a starting point at best. Two homes the same size can need very different systems depending on insulation, windows, air leaks, ceiling height, sun exposure and whether you're heating a 1920s bungalow or a 2015 build.

The right way: a load calculation

A proper installer runs a load calculation, often called Manual J, using your home's real measurements and construction. That's the number the system should be sized to.

Try the quick estimator

Want a ballpark before your quote? Use our heat pump size estimator. It gives a rough range, not a final answer.

What to ask your installer

• Did you run a load calculation, and can I see it?
• How does the system perform at our coldest design temperature?
• Is a variable-speed system a better fit for my home?