At 40 to 45 btus per square foot you d need a 100 000 to 112 500 btu.
Gas furnace btu per square foot.
And in cold climates multiply the square foot number by 30 40.
It is approximately the energy needed to heat one pound of water by 1 degree fahrenheit.
For example in zone 3 to 4 which typically requires 40 45 btu per square feet you can determine that a 2 500 square foot home would need a 100 000 to 112 000 btu furnace.
For cooler climates a very broad estimate of furnace sizing is to select one that generates 40 to 45 btus per square foot.
A more efficient furnace will output more btus of heat than a less efficient furnace with the same btu rating.
Once you have the total square footage just multiply that number by 20 to find how many btus per hour you d need to heat or cool the space.
To learn how to adjust btu per square foot for special conditions scroll down.
But before we buy an 80 000 btu furnace there s furnace efficiency to consider as well.
1 watt is approximately 3 412 btu per hour.
Another variable in determining your energy needs is space both in terms of square footage and cubic footage.
Furnaces are rated on their btus of energy consumption not their btus of energy output.
The british thermal unit or btu is an energy unit.
Average square and cubic footage.
Then to calculate the output on a given gas furnace multiply it s efficiency rating by it s listed input rating to determine the actual btu output of heat.
1900 square feet x 40 heating factor from the chart above 76 000 btu required to heat your home.
2 000 square feet x 40 btus 80 000 btu output required thanks to the equation we know we need 80 000 btus of heat.
For example if you re trying to heat or cool 1 000 square feet you would multiply 1 000 by 20 and get 20 000 btus per hour.
Instead natural gas may be priced as dollars per therm.
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.
Another quick and easy way to estimate the number of btu s required is with this helpful chart.
Therefore the price per 100 cubic feet divided by 1 037 is equal to the price per therm.
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.
1 btu 1 055 joules 252 calories 0 293 watt hour or the energy released by burning one match.
