Heat Pumps vs Gas Furnaces The Real Cost Compariso

I had a client named Theresa call me last winter. Her gas furnace was 22 years old. It still ran, but it made a noise like a dying animal. She knew she had to replace it. She’d heard about heat pumps. Her neighbor installed one and said it was amazing. But she also heard that heat pumps don’t work in cold weather. She asked me, “What should I do?” I told her the real answer: it depends on your house, your climate, and your electric rate.

Heat pumps are not new. They’ve been around for decades. But the new cold‑climate heat pumps are a different beast. They can extract heat from outdoor air down to -13°F or lower. That’s most of the continental U.S., except the very northern tip of Minnesota and North Dakota. In Denver, where I live, a cold‑climate heat pump works fine. In Theresa’s house in Boulder, it would work fine too.

The question is not whether a heat pump can work. It’s whether a heat pump will save you money compared to a gas furnace. And that depends entirely on the price of electricity versus the price of gas.

Here’s the math. A gas furnace with 95% efficiency converts one therm of natural gas (about 29.3 kWh of heat content) into 27.8 kWh of heat for your house. At $1.20 per therm, that’s $1.20 for 27.8 kWh of heat. That’s $0.043 per kWh of heat. A heat pump with a Coefficient of Performance (COP) of 3.0 moves 3 kWh of heat for every 1 kWh of electricity it consumes. At an electric rate of $0.14 per kWh, that’s $0.14 for 3 kWh of heat, or $0.047 per kWh of heat. Almost the same. If electricity is $0.15, the heat pump is more expensive. If gas is $1.00 per therm, the gas furnace is cheaper. If the heat pump’s COP is 4.0, the math changes.

Theresa’s electric rate was $0.14 per kWh. Her gas rate was $1.10 per therm. A 95% furnace would cost her $0.039 per kWh of heat. A COP 3.0 heat pump would cost $0.047 per kWh of heat. The gas furnace was cheaper to operate. But her furnace was old. A new 95% furnace would cost about $4,000 installed. A new cold‑climate heat pump would cost about $8,000. The heat pump was twice as expensive upfront. But the heat pump also provides cooling in summer. Her old AC was 14 SEER and nearing end of life. If she replaced both the furnace and the AC, that would be about $9,000. A heat pump that does both heating and cooling was $8,000. So she could replace two units with one, for less money.

That’s the hidden advantage of heat pumps. They combine heating and cooling. If you need to replace both, a heat pump can be cheaper than a new furnace plus a new AC. And the heat pump will be more efficient for cooling than a standard AC of the same SEER rating.

Theresa also qualified for a $2,000 federal tax credit for heat pumps. That dropped her net cost to $6,000. The furnace plus AC would have been $9,000 with no tax credit. Now the heat pump was $3,000 cheaper upfront. And the operating cost difference was small. So she went with the heat pump.

She’s had it for a year now. Her winter heating bills were about $15 higher per month than her old gas furnace, but her summer cooling bills were $30 lower because the heat pump is more efficient than her old AC. Net annual savings about $180. Plus she got rid of her gas meter and saved the $10 monthly customer charge. She’s happy.

But not everyone has the same numbers. I have another client, Steve, in rural Iowa. His electric rate is $0.12 per kWh. Gas is $0.80 per therm. A gas furnace is much cheaper to operate. His old furnace works fine. He doesn’t need a new AC because he uses window units. For him, a heat pump makes no sense. The payback would be 20 years.

The key variables are your local fuel prices and your climate. The Department of Energy has a simple rule of thumb. If your electric rate divided by your gas rate is less than 2.5, a heat pump might save you money. Wait, let me be precise. Compare the cost per BTU. A heat pump with COP 3.0 gives you 3 units of heat per 1 unit of electricity. At $0.15 per kWh, that’s $0.05 per kWh of heat. A 95% furnace gives you 0.95 therms of heat per therm of gas. At $1.20 per therm, that’s $1.26 per therm of heat, which is $0.043 per kWh of heat. The furnace is cheaper. So the breakeven is when $0.15 / $1.20 is about 0.125, not 2.5. Let me simplify.

Better to use an online calculator. But in general, if you pay more than $0.18 per kWh for electricity and less than $1.00 per therm for gas, a gas furnace is likely cheaper to operate. If you pay less than $0.12 per kWh and more than $1.50 per therm for gas, a heat pump is likely cheaper. Most people are in between.

Now, there’s another factor: climate. In very cold climates, the heat pump’s COP drops. At 0°F, a cold‑climate heat pump might have a COP of 2.0 instead of 3.0. That makes it less efficient. At -10°F, COP might be 1.5. So you need backup heat. That could be electric resistance strips or a gas furnace. Dual‑fuel systems are popular. The heat pump runs down to about 25°F, then the gas furnace takes over. That gives you the best of both worlds. But it also adds complexity and cost.

Steve in Iowa could consider a dual‑fuel system. But his gas is so cheap that he’s better off sticking with gas.

The other big change is the Inflation Reduction Act. It offers $2,000 tax credits for heat pumps, plus rebates for low‑ and moderate‑income households. In some states, there are additional incentives. In Colorado, Xcel offers a $1,000 rebate for cold‑climate heat pumps. Between federal and state, Theresa got $3,000 off.

The heat pump market is evolving fast. Ten years ago, heat pumps were not competitive in cold climates. Today, they are. Five years from now, they’ll be even better.

If you’re replacing a failed AC and your furnace is also old, a heat pump is a strong candidate. If your furnace works fine and you live in a cold climate, wait until it fails. Then evaluate.

I have a tool that helps with the comparison.