Recommended BTUs:
Climate Zone BTU Range:
It is very important to size your heating and cooling system correctly for your home. If a
furnace or air conditioner is too small, it will run constantly and not be able to comfortably
heat or cool the space.
On the coldest or hottest days, the system will not be able to keep up. Alternatively, if the
system is sized too large, it will heat or cool the space too quickly, which will cause it to
cycle on and off more frequently, causing unnecessary wear and shortening the lifespan of the
system.
According to the Star Tribune, the constant cycling of an oversized furnace is less comfortable as well since certain areas of the home heat up too quickly and become too hot before the system turns off.[1] Both furnaces that are too small and too large will also cost you more to run, while still leaving your home uncomfortable. They’ll also wear out faster, costing you more in replacement costs.
There are several factors to consider when trying to figure out how many BTUs your furnace should output.
Experts suggest between 30 and 60 BTUs of heat per square foot of living space, which is a pretty
wide range.
The location of your home is a major factor in how many BTUs you’ll need. A home in the northern
region of the US will require more BTUs to heat than a home in the southern region because it
gets significantly colder in the north.
The ranges in the heating climate zone chart above assume a home with average insulation. Homes
that are poorly insulated may require 10% more BTUs due to heat loss through thermal transfer.
Very well-insulated homes and homes with a tight building envelope will require 10% fewer BTUs
to heat since very little heat is lost. It may be worth adding insulation to attic spaces and
walls to reduce the amount of energy needed to heat the home.
An energy audit can help you determine if this is necessary, or if you have other areas of
thermal transfer that can be eliminated to help lower your heating bills.