Furnace System GuideFurnace tool
Furnace Operating Cost Calculator
Estimate annual heating therms and natural gas cost from furnace input BTU, AFUE, daily run hours, season length, and your gas rate.
Screening estimate only.A professional Manual J load calculation is authoritative for final furnace sizing and equipment selection. Confirm every result with a licensed HVAC professional.
Screening result
- Annual therms
- Annual cost
Fine Print and Sources
Screening estimate only. These tools use only the values you enter and simple planning math. A professional Manual J load calculation is authoritative for equipment sizing, room loads, and final purchase decisions. Confirm with a pro before you buy.
Method: one therm equals 100,000 BTU. Annual therms equal input BTU per hour times run hours per day times season days, divided by 100,000. Annual cost equals therms times your gas rate. Actual cost varies with thermostat settings, weather, duct losses, and part-load behavior.
- US Department of Energy furnaces and boilers: explains furnace efficiency, AFUE, and why proper sizing and a load calculation matter.
- Energy Star furnaces: describes AFUE tiers and how higher-efficiency condensing furnaces reduce fuel use.
- US EIA natural gas prices: use current residential gas prices to set a realistic dollars-per-therm rate.