Heat Pump vs Gas Furnace Calculator
A heat pump vs gas furnace calculator compares yearly fuel cost: for 40 million BTU, a 95% AFUE furnace costs $505 and a COP 3.0 heat pump costs $586.
Heat pump vs gas furnace calculator
A heat pump vs gas furnace calculator turns one yearly heating load into two bills. With 40 million BTU of heat needed, a 95% AFUE gas furnace at $1.20 a therm costs $505 a year. A heat pump at COP 3.0 and $0.15 a kWh costs $586. The gas side wins by $81 at those prices.
Change any of the five inputs and the gap moves, sometimes a lot.
The two formulas
Heat pump: kWh = annual BTU ÷ (COP × 3,412), then cost = kWh × electricity rate. One kWh equals 3,412 BTU.
Gas furnace: therms = annual BTU ÷ (AFUE ÷ 100 × 100,000), then cost = therms × gas rate. One therm equals 100,000 BTU.
Both lines answer the same question: how much money buys 40 million BTU of heat in the house.
Worked examples
Defaults: 40,000,000 BTU, COP 3.0, $0.15 per kWh, AFUE 95%, $1.20 per therm.
- Heat pump: 40,000,000 ÷ (3 × 3,412) = 3,907.8 kWh, × $0.15 = $586
- Gas: 40,000,000 ÷ (0.95 × 100,000) = 421.1 therms, × $1.20 = $505
An older furnace against a middling heat pump: COP 2.5, AFUE 80%, same prices.
- Heat pump: 40,000,000 ÷ (2.5 × 3,412) = 4,689.3 kWh, × $0.15 = $703
- Gas: 40,000,000 ÷ (0.80 × 100,000) = 500 therms, × $1.20 = $600
A bigger house with costly gas: 60,000,000 BTU, COP 3.5, $0.20 per kWh, AFUE 92%, $1.50 per therm.
- Heat pump: 60,000,000 ÷ (3.5 × 3,412) = 5,024.3 kWh, × $0.20 = $1,005
- Gas: 60,000,000 ÷ (0.92 × 100,000) = 652.2 therms, × $1.50 = $978
Cost to deliver one million BTU
This table uses 1,000,000 BTU so you can scan across prices.
| Heat source | At $0.15 per kWh | At $0.10 per kWh | At $0.25 per kWh |
|---|---|---|---|
| Heat pump, COP 2.0 | $21.98 | $14.65 | $36.64 |
| Heat pump, COP 2.5 | $17.58 | $11.72 | $29.31 |
| Heat pump, COP 3.0 | $14.65 | $9.77 | $24.42 |
| Heat pump, COP 3.5 | $12.56 | $8.37 | $20.93 |
| Heat pump, COP 4.0 | $10.99 | $7.33 | $18.32 |
| Gas furnace | At $0.80 per therm | At $1.20 per therm | At $2.00 per therm |
|---|---|---|---|
| AFUE 80% | $10.00 | $15.00 | $25.00 |
| AFUE 90% | $8.89 | $13.33 | $22.22 |
| AFUE 95% | $8.42 | $12.63 | $21.05 |
Find the heat pump row and the furnace column for your prices and compare the two dollar amounts. Multiply by your yearly BTU in millions to get the annual figure.
What the break-even looks like
At $0.15 per kWh, $1.20 per therm and a 95% furnace, the heat pump has to reach COP 3.48 to tie. At $0.10 per kWh the same furnace is matched at COP 2.3. At $0.25 per kWh it needs COP 5.8, which no ordinary heat pump reaches in cold weather.
COP changes with the weather
The COP printed in a brochure is measured at a stated outdoor temperature. In real winters it moves up and down. Use a seasonal figure from the manufacturer’s data for your climate, or run the calculator twice with a mild-weather COP and a cold-weather COP to see the range.
Mistakes to avoid
- Entering the furnace’s input rating (BTU per hour) as the yearly load. The load field is a yearly total of heat delivered.
- Using the heat pump’s cooling efficiency. SEER and EER describe cooling, so look for a heating COP or HSPF figure converted to COP.
- Forgetting standing gas charges or electric delivery fees that stay the same either way.
- Treating the result as the whole decision. Installation cost, existing ductwork and electrical capacity matter as much.
Related tools
If you are replacing equipment anyway, the furnace and AC replacement cost calculator totals the equipment and labor. Use the heat loss calculator for a rough load, the furnace size calculator to check capacity, and the electricity cost calculator to see what a given kWh figure costs on your rate. A licensed HVAC contractor should size and install either system.
Frequently asked questions
What is COP and why does it change the running cost?
COP is the heat delivered divided by the electricity used. A COP of 3 means 3 units of heat for every 1 unit of electricity, so a heat pump at COP 3 uses a third of the electricity a plain electric heater would. Higher COP means lower cost, and COP drops as outdoor temperature falls, so use a figure for your climate.
What is AFUE and how does it affect the gas side?
AFUE is the share of the fuel's energy that ends up as heat in the house. A 95% AFUE furnace sends 95 cents of every fuel dollar into the home and loses 5 cents up the flue. An old 80% unit loses 20 cents, so 40 million BTU of heat takes 500 therms instead of 421.
Is a heat pump always cheaper to run than a gas furnace?
No. At the defaults here ($0.15 per kWh, $1.20 per therm, 95% AFUE) a heat pump needs a COP of about 3.5 to match the furnace. With cheap electricity or expensive gas the heat pump wins easily; with the opposite prices the furnace can win.
Does this include equipment and installation cost?
No. The two results are yearly fuel and electricity cost only. Purchase price, installation, ductwork changes, electrical work, maintenance and any incentives are separate and often decide the comparison over ten or fifteen years.
How do I find my annual heating load in BTU?
Add up the heat your home needs over a winter. Your gas bill gives a starting point: multiply annual therms by 100,000 BTU and by your furnace's AFUE as a decimal. A professional load calculation is better, and our heat loss calculator can give a rough figure.
Estimates only. Verify quantities with your supplier before purchasing.