Fuel Cost Comparison Calculator — Natural Gas vs Propane vs Electric Heat
Compare annual heating costs for natural gas, propane, and electric heat based on your home's heating load, local fuel prices, and equipment efficiency.
MMBtu/yr
$/therm
%
$/gallon
%
$/kWh
Formulas Used
Annual fuel cost (general):
Annual Cost = (Heating Load [MMBtu] / Efficiency) × (Fuel Price / Fuel Energy Density)
Natural Gas:
Therms needed = Heating Load [MMBtu] ÷ (AFUE/100) ÷ 0.1 [MMBtu/therm] Annual Cost = Therms needed × Price [$/therm]
Propane:
Gallons needed = Heating Load [MMBtu] ÷ (AFUE/100) ÷ 0.09150 [MMBtu/gal] Annual Cost = Gallons needed × Price [$/gallon]
Electric (Resistance or Heat Pump):
kWh needed = Heating Load [MMBtu] ÷ COP ÷ 0.003412 [MMBtu/kWh] Annual Cost = kWh needed × Price [$/kWh] COP (Coefficient of Performance) = Useful Heat Output / Electrical Energy Input Resistance heat: COP = 1.0 (100% efficient by definition) Heat pump (mild): COP ≈ 2.5 Heat pump (cold): COP ≈ 1.8
Effective cost per MMBtu delivered:
Cost/MMBtu = Annual Cost ÷ Heating Load [MMBtu]
Assumptions & References
- 1 therm = 100,000 BTU = 0.1 MMBtu (U.S. Energy Information Administration).
- 1 gallon propane = 91,500 BTU = 0.0915 MMBtu (DOE/EIA standard value).
- 1 kWh = 3,412 BTU = 0.003412 MMBtu (thermodynamic equivalence).
- AFUE (Annual Fuel Utilization Efficiency) measures how much fuel energy is converted to useful heat over a heating season. Minimum federal standard for gas furnaces is 80% AFUE; high-efficiency units reach 95–98%.
- COP (Coefficient of Performance) for heat pumps is the ratio of heat delivered to electricity consumed. COP > 1 because heat pumps move heat rather than generate it. Actual COP varies with outdoor temperature.
- Default heating load of 80 MMBtu/year is representative of a ~2,000 sq ft home in a moderate U.S. climate (ASHRAE climate zone 4–5). Actual loads depend on insulation, climate, and occupancy.
- Default prices: natural gas $1.20/therm, propane $2.50/gal, electricity $0.13/kWh — approximate 2024 U.S. national averages (EIA Monthly Energy Review).
- This calculator compares fuel costs only. It does not include equipment purchase, installation, maintenance, or carbon costs.
- Source: U.S. EIA — Heating Fuel Comparison Calculator; ASHRAE Handbook of Fundamentals.