Garden Heating fuel cost comparison
You cannot compare a therm of gas with a kilowatt-hour of electricity directly, which is exactly why heating costs are so hard to reason about. Converting everything to the cost of one million BTU of delivered heat, after efficiency losses, puts every option on the same axis.
How this is calculated
Cost per million BTU = (1,000,000 ÷ energy content of the fuel ÷ system efficiency) × price. Electricity holds 3,412 BTU per kWh, natural gas 100,000 per therm, propane 91,500 per gallon, heating oil 138,500 per gallon. A heat pump divides by its COP instead, because it moves heat rather than making it.
Source: Fuel energy contents and the cost-per-MMBtu method follow US Department of Energy / EIA guidance
Worth knowing: A heat pump's COP falls as it gets colder, so a single figure flatters it in a cold climate — the seasonal average (HSPF) is what matters over a winter, and cold-climate models hold efficiency far better than older ones. This compares fuel cost only, not equipment cost, installation, or the fact that many homes cannot get natural gas at all.
Common questions
What is a COP?
Coefficient of performance — how many units of heat a heat pump delivers per unit of electricity it consumes. A COP of 3 means three times as much heat out as electricity in, which is possible because it moves existing heat rather than generating it. That is why heat pumps beat electric resistance so decisively.
Why is electric resistance always the most expensive?
Because it is capped at 100% efficiency — one unit of electricity becomes exactly one unit of heat. A heat pump running at COP 3 does the same job for a third of the electricity. Any electric heater sold as "100% efficient" is telling the truth and hiding the point.
Does this include the cost of the equipment?
No — fuel only. A heat pump may cost far more to install than a gas furnace while costing less to run, so the payback period depends on both. Use this to understand the running side, then weigh installed cost separately.
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