Forced Air Furnace Btu Calculator

Natural gas for a furnace is priced by the therm or per 100 000 btus.

Forced air furnace btu calculator.

Furnaces are rated on their btus of energy consumption not their btus of energy output. If that same furnace has an efficiency of 95 the furnace will produce 95 000 btu of heat. For example if a furnace has a listed input rating of 90 000 btu s and an efficiency rating of 80 it will produce 90 000 btu input x 80 efficiency 72 000 btu actual output. This hvac calculator is the closest estimate to the actual manual j calculation done by hvac pros.

In the example above using an 80 efficient furnace the 2000 square foot home above would require a 100 000 btu input furnace which will produce the necessary 80 000 btu s output of heat. 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. Btu can also be used pragmatically as a point of reference for the amount of heat that an appliance generates. The higher the btu rating of an appliance the greater the heating capacity.

The heat load estimate is based on your climate region total square footage number of rooms or zones you want ceiling height insulation type number of windows and doors. 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. To avoid these headaches follow our detailed guide on how to accurately calculate the furnace size that is most suitable for your home. A heating degree day calculation using the month of july as a factor is a more precise way of estimating furnace size.

Variables let s talk about all of the variables that come into play when selecting a new air conditioner system or furnace. This hvac load calculator quickly estimates the size of your heating and cooling system in btu s. Different furnaces of the same input btu have different efficiencies measured in percentages. For example a furnace with an input btu can have an efficiency of 80.

That means the furnace will produce 80 000 btu of heat. The size of a furnace is based on how much heat it can produce in an hour as measured in btus or british thermal units.