Heat pump vs furnace running cost
Put in what you actually pay and what your house actually needs. The calculator converts one annual heating load into gas cost and electricity cost, shows every step, and tells you the electricity price at which the two are equal.
Your scenario
The arithmetic, step by step
This is a scenario, not a prediction. It answers one question: at the prices and ratings you typed, what would each fuel cost to deliver the same amount of heat? It does not forecast your bill. HSPF2 is measured under a standard rating procedure at fixed test conditions, so a real winter in a real house, with its own temperatures, thermostat habits, duct or head placement, defrost cycles and any backup heat, will not match it. A colder climate than the rating condition pushes a heat pump's seasonal efficiency down; a milder one pushes it up. Nothing here includes equipment price, installation, maintenance, rebates or tax credits.
The formulas this calculator uses
There are only four, and they are all definitions rather than models. A therm is 100,000 BTU. A kilowatt-hour is 3,412.14 BTU. AFUE is the share of the fuel's energy that reaches the house over a season. HSPF2 is seasonal heating output in BTU divided by electricity input in watt-hours.
The implied seasonal coefficient of performance is the same HSPF2 figure in consistent units: HSPF2 ÷ 3.41214. An HSPF2 of 10.0 is a COP of about 2.93, meaning roughly 2.9 units of heat delivered per unit of electricity drawn, under the rating conditions.
Why the gas-use route is the honest one
A heating load in BTU is hard to know. A gas bill is not. If you burned 600 therms through an 80% AFUE furnace, 60 million BTU of gas energy went in and about 48 million BTU of heat came out into the rooms. That 48 million BTU is the load, and it is what the heat pump would have to deliver instead. Starting from the bill keeps the comparison grounded in something you can check, rather than in a heat-loss estimate neither of us has made.
Two cautions. A bill includes any gas used for water heating, cooking or a dryer on the same meter, so subtract a summer month's use times twelve before you start if the meter is shared. And a single winter can be colder or milder than normal, which moves the load without anything changing in the house.
What this calculator deliberately does not do
- It does not quote installed prices. The ENERGY STAR dataset contains no prices, and no verified regional installed-cost data is in this site yet. Any figure here would be invented.
- It does not size equipment. Sizing needs a room-by-room heat-loss calculation, not a bill.
- It does not model backup heat. When outdoor temperature drops below the point where a system's capacity meets the load, something else makes up the difference, usually electric resistance heat at a COP of 1. That raises real-world cost in a way a seasonal rating does not show. The published 5°F capacity on each system page is where to start on that question.
- It does not include rebates or tax credits. Those change the purchase decision, not the running cost.
For what the ratings themselves mean, read SEER2 vs HSPF2. For where every specification on this site comes from, see the methodology page.