Heat Pump vs Gas Furnace Cost Calculator

Heat needed per year (MMBtu)

How much heat your home needs in a year, in million BTU (MMBtu). It is the heat delivered to the rooms, not the fuel you burn.

1. Gas furnace: add up the therms on your gas bills for the heating months. Subtract your non-heating baseline (a summer month's therms x the number of heating months). Multiply by your furnace efficiency (AFUE), and divide by 10. Example: 500 heating therms x 0.95 = 475, divided by 10 is 47.5 MMBtu.
2. Propane or oil: multiply gallons used by the energy per gallon (about 91,500 BTU for propane and 138,500 for heating oil), then by the furnace efficiency, and divide by 1,000,000.
3. Or ask a heating contractor for a load calculation (often called a Manual J), which estimates the heat your home needs.

The pre-filled 50 MMBtu is only an example. Colder climates and larger or leakier homes need more.

Gas furnace efficiency (AFUE)

AFUE is the share of the fuel your furnace turns into heat. Enter it as a decimal: 95% is 0.95.

1. Look at the label or data plate on the furnace (inside the cabinet or on the side), or the yellow EnergyGuide label on a new one.
2. Search the brand and model number with "AFUE" to find it.

Cannot find it? Older furnaces are often around 0.6 to 0.8, standard efficiency about 0.8, and high-efficiency models 0.9 to 0.98.

Gas price ($ per therm)

A therm is 100,000 BTU of natural gas, the unit many gas bills use.

1. Look at your gas bill for a "price per therm" or "gas charge" line.
2. If your bill is in ccf, one ccf is about one therm. If it is in Mcf (1,000 cubic feet), divide the price by about 10.
3. If you only see totals, divide the total gas charges by the therms used for an all-in price.

Heat pump efficiency (HSPF)

HSPF is the heat a heat pump delivers over a season for each unit of electricity. Higher is better.

1. For a heat pump you already have, check the label or data plate, or look up the model number in the AHRI directory (opens in a new tab).
2. For one you are considering, ask the installer for the HSPF or HSPF2 rating, or look it up on the manufacturer's specification sheet.
3. Newer HSPF2 ratings use a stricter test and are numerically lower than older HSPF ratings. Use the number for the model you are comparing.

A common range is roughly 8 to 10. Cold-climate heat pumps are designed to hold up better in very cold weather.

Electricity rate ($ per kWh)

This is what your utility charges for each kilowatt-hour (kWh) of electricity.

1. Open your latest electric bill (paper, email, or your utility's website or app).
2. Look for a line called "price per kWh", "energy charge" or "rate". It is often shown in cents, so divide by 100 (17 cents is 0.17).
3. If the bill only shows totals, divide the total electricity charges by the kWh used. This quick all-in rate includes fixed fees, so it runs a little high.
4. If your rate changes by time of day or by how much you use, use an average, or the rate that applies when you use the appliance most.

No bill handy? About 17 cents is a rough US average, so the pre-filled value is a fair start. Rates vary a lot by state and utility, so your own number is better.

See the average residential rate for every state