Gas vs Electric Heating Calculator

How to use the gas vs electric heating calculator

This tool settles the gas-versus-electric heating argument the only fair way, by pricing the exact same amount of useful heat from each side. You enter how much heat you need in therm-equivalents, the price of gas and the price of electricity, your furnace AFUE, and whether the electric system is a heat pump or plain resistance heat, and the tool returns the gas cost, the electric cost, and the winner with the gap between them.

Everything is pre-filled with a representative example — 50 therm-equivalents at $1.50 per therm and 0.95 AFUE, against $0.175 per kWh at COP 3 — so you can watch it work before swapping in your own numbers. The point is that efficiency is what makes the comparison honest, and both sides get it applied.

Start with the useful heat needed, entered in therm-equivalents: the heat actually delivered into your rooms, not the raw fuel burned to make it. One therm-equivalent is the same quantity of warmth whether it comes from gas or electricity, which is what makes the comparison legitimate, because both fuels are then charged for delivering identical results.

The default of 50 is a fair stand-in for a chunk of a heating season. If you know a month delivered heat, enter it; if you do not, leave the default and read the result as a per-50-unit comparison you can scale linearly. Doubling the heat doubles both costs, so the winner and the percentage gap stay the same however you scale it.

Next come the two rates and the furnace AFUE. Annual Fuel Utilization Efficiency is the share of the gas energy that becomes usable heat: 0.95 means 95 percent of the energy in the gas ends up warming the house and the other 5 percent goes up the flue. Because of that loss, the gas energy you must buy is the useful heat divided by AFUE, not the useful heat itself.

Enter the rating on your own furnace. Modern condensing furnaces sit around 0.90 to 0.98 while older atmospheric units run considerably lower, and the current federal minimum for new non-weatherized gas furnaces is 80 percent AFUE, a level unchanged since 2007; the Department of Energy finalised a rule in December 2023 raising it to 95 percent for units manufactured on and after 18 December 2028.

That 95 percent rule is in force but it is not settled law. The DC Circuit upheld it in November 2025, and in June 2026 the Supreme Court vacated that decision and sent the case back for reconsideration. Treat the 2028 date as the current requirement rather than a certainty, and check where the case stands if you are planning a replacement around it.

How much does heat pump versus resistance change it?

Then choose the electric type, because it changes the answer completely. A therm of useful heat is about 29.3 kWh of energy, and a heat pump coefficient of performance divides that figure: a COP of 3 means the unit moves three units of heat for every one unit of electricity, so it needs only a third of the electricity a resistance heater would.

Resistance heat is COP 1, where every kilowatt-hour of electricity becomes one kilowatt-hour of heat and nothing is multiplied. Pick heat pump for a modern system in mild conditions and resistance for baseboards, electric furnaces or strip heat. Read the output as three numbers — gas cost, electric cost, and the winner with the dollar gap — and remember the result is a running-cost comparison, not equipment advice and not a bill prediction.

The formula, worked line by line

The comparison is built on one idea: price the same useful heat from each side. On the gas side you divide the useful heat by AFUE to get the gas energy you actually have to buy, then multiply by the gas rate.

On the electric side you convert the useful heat to kilowatt-hours, divide by the system coefficient of performance to get the electricity it actually draws, then multiply by the electric rate. Skip either efficiency term and the answer is meaningless, because you would be comparing fuel purchased against heat delivered.

The two efficiency terms work in opposite directions, which is the thing worth internalising. AFUE is always below 1 and therefore always increases the gas you must buy: a 95 percent furnace needs 1.053 units of gas energy for every unit of heat delivered.

COP is normally above 1 and therefore reduces the electricity drawn: a COP of 3 needs 0.333 units of electrical energy for every unit of heat. Nothing is being created from nothing — a heat pump moves ambient heat rather than making it, which is why it can exceed 100 percent while a furnace never can.

gas cost = (therms ÷ AFUE) × gas rate
electric kWh = therms × 29.3
electric cost = (electric kWh ÷ COP) × electric rate
cost per million BTU delivered = the same expressions run on 10 therm-equivalents

Three caveats that decide real outcomes. COP is not a constant; it falls as the outdoor temperature falls, which is why the Northeast Energy Efficiency Partnerships cold-climate specification sets a floor of COP 1.75 at 5°F at maximum capacity and why many systems fall back to resistance strips in deep cold, landing on the bottom row of the table.

Ratings changed too: HSPF2 and SEER2 replaced HSPF and SEER for US equipment on 1 January 2023 under the appendix M1 test procedure, so an HSPF2 of 7.5, the split-system minimum, corresponds to a seasonal COP of about 2.2. And this is running cost only — it says nothing about equipment price, installation, rebates or cooling, and it is not financial advice.

Questions people ask