On the other hand if you live in a 5 000 square foot home get a unit with 100 000 btus.
80000 btu furnace square footage.
If that same furnace has an efficiency of 95 the furnace will produce 95 000 btu of heat.
A more efficient furnace will output more btus of heat than a less efficient furnace with the same btu rating.
But there are also rule of thumb estimations you can use to pick a furnace size for your home.
Different furnaces of the same input btu have different efficiencies measured in percentages.
You need a heater with at least a 21 780 btu output.
For cooler climates a very broad estimate of furnace sizing is to select one that generates 40 to.
It s been developed by fireplace industry experts.
For instance a furnace with 80 000 btu input and an 80 efficiency rating will only produce 64 000 btus.
2 000 square feet x 40 btus 80 000 btu output required.
For this example using an 80 efficient furnace the 1900 square foot home above would require a 90 000 btu input furnace that produces 72 000 btu s of heating which is close enough to the 76 000 btu s required using the climate heating factor.
Thanks to the equation we know we need 80 000 btus of heat.
Our btu calculator is the best there is for fireplaces stoves and inserts.
If your house measures between 2 035 and 2 070 square feet a 80 000 btu per hour unit is best and more than 3 390 square feet requires a 120 000 btu per hour furnace.
But before we buy an 80 000 btu furnace there s furnace efficiency to consider as well.
Btu charts furnace output and air conditioner size for a bungalow bungalow area sq ft furnace output btu hr air conditioner size ton built after year 1980 built before year 1980 built after year 1980 built before year 1980 up to readmore.
That means the furnace will produce 80 000 btu of heat.
For example if your uninsulated garage is 484 square feet your formula is 484 200 x 9 000 or 21 780.
For example a furnace with an input btu can have an efficiency of 80.
Consult an hvac expert for.
For example if a furnace is rated at 100 000 btus and is 80 efficient then the heat output will be 80 000 btus 100 000 x 8.
Find a heater with a btu output that matches your results.