Household Heating Tool
Gas Furnace Operating Cost Calculator
Calculate residential gas furnace heating costs by input capacity (Btu/hr) or heating output rating with AFUE efficiency percentage, runtime hours, and therm gas pricing.
Gas Furnace Cost Calculator Inputs
Estimated Gas Furnace Operating Cost
Calculated Input Capacity
100,000 Btu/hr
Therms Consumed
150.0 therms
Daily Heating Cost
$8.75 / day
Estimated Heating Period Cost (30 days)
$262.50
At 100,000 Btu/hr input and 5 runtime hours/day over 30 days, the furnace uses 150 therms of gas ($262.50 total at $1.75/therm).
Calculation Assumptions & Limitations
Formula: Input Btu/hr = Heating Output Btu/hr ÷ (AFUE % ÷ 100). Therms Used = Input Btu/hr × Total Hours ÷ 100,000. Usage Cost = Therms × Gas Rate per Therm.
- Furnace heating output rated at 80,000 Btu/hr with 80% AFUE seasonal efficiency (input capacity: 100,000 Btu/hr).
- Burner runtime estimated at 5 hours per day over 30 active heating days (150 total runtime hours).
- Natural gas pricing assumed at $1.75 per therm (1 therm = 100,000 Btu).
- Calculates volumetric natural gas usage cost only. Electricity needed for the furnace blower motor (typically 300W to 800W) is not included.
- Thermostat cycling, outdoor winter temperatures, building insulation, and duct losses alter actual burner firing hours.
- Utility fixed monthly customer charges, delivery fees, and taxes are excluded.