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’s AFUE, and whether the electric system is a heat pump or plain resistance heat. 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, 0.95 AFUE, $0.175 per kWh, heat pump), so you can watch it work before swapping in your own numbers.

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 honest: both fuels are charged for delivering the identical amount of heat. The default of 50 is a fair stand-in for a chunk of a heating season; if you know a month’s delivered heat, enter that, and if you don’t, leave the default and read the result as a per-50-units comparison you can scale.

Next come the two rates and the furnace’s AFUE. AFUE — Annual Fuel Utilization Efficiency — is the share of the gas energy that becomes usable heat: 0.95 means 95% of the energy in the gas ends up warming the house and the other 5% 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 your furnace’s rating (modern condensing furnaces sit around 0.90–0.98; older units run lower) along with your gas price per therm and your electricity price per kWh.

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’s coefficient of performance (COP) divides that figure — a COP of 3 means the heat pump moves three units of heat for every one unit of electricity, so it needs only a third of the electricity. Resistance heat is COP 1: every kilowatt-hour of electricity becomes one kilowatt-hour of heat and nothing is multiplied. Pick “Heat pump (COP 3)” for a modern system in mild conditions, or “Resistance (COP 1)” for baseboard heaters, electric furnaces, or strip heat.

Read the output as three numbers: the gas cost, the electric cost, and the winner with the dollar gap. On the defaults gas comes in at $78.95 and the heat pump at $85.46, so gas wins by $6.51 — close enough that your own rates can flip it. That is the real lesson: cheap gas against expensive electricity favors gas, the reverse favors electric, and your local heat-pump COP shifts the whole picture, so plug in your own bills. Note too how far a heat pump closes the gap — switch the same job to resistance heat and the electric cost jumps to $256.38, and gas wins in a landslide.

The formula

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’s COP to get the electricity it actually draws, then multiply by the electric rate:

gas cost = (therms ÷ AFUE) × gas rate
electric kWh = therms × 29.3
electric cost = (electric kWh ÷ COP) × electric rate

Worked example with the defaults — 50 therm-equivalents of useful heat. Gas: (50 ÷ 0.95) × $1.50 = $78.95. Electric as a heat pump: 50 × 29.3 = 1465 kWh, then (1465 ÷ 3) × $0.175 = 488.3 kWh × $0.175 = $85.46. Gas wins by $6.51 ($85.46 − $78.95). Swap the heat pump for resistance heat (COP 1) and the electricity is no longer divided: 1465 × $0.175 = $256.38, and gas wins big.

Two numbers do the heavy lifting. The 29.3 kWh per therm is the energy in a therm expressed in kilowatt-hours, so it converts useful heat from one fuel’s units to the other’s. AFUE handles the gas side’s loss: at 0.95, only 95% of the gas energy becomes heat, so you buy useful ÷ 0.95 worth of gas to deliver the heat you want. The heat pump’s COP works the opposite way on the electric side — it divides the electricity needed, which is why a COP-3 heat pump can run neck-and-neck with cheap gas while resistance heat cannot.

Frequently asked questions