Heat Pump vs Furnace After One Year of Real Data

Last March I pulled out a 14-year-old 80,000 BTU gas furnace and replaced it with a cold-climate heat pump. I live in zone 5, where January lows hit single digits a few times each winter and February isn't much better. People told me I'd freeze. People told me my electric bill would triple. I kept a spreadsheet anyway and tracked every month for a full year. Here's what actually happened.

The Numbers Month by Month

My old furnace burned natural gas at about 96 AFUE, which was decent. The gas bill during heating season ran $145 to $210 per month, depending on how cold things got. In the shoulder months it dropped to $40 or so for the water heater and cooking. Total heating cost for the prior winter was around $1,380.

The heat pump is a 3-ton cold-climate unit rated at COP 3.2 down to 17F and COP 2.0 at 5F. In practice my electricity for heating added roughly $85 to my bill in October, $130 in November, $155 in December, $190 in January, $170 in February, and $105 in March. That's $835 total for the heating season, or about $545 less than gas. My gas bill dropped to under $25 every month since the furnace isn't running.

Where it gets interesting is summer. The old system had a separate 2.5-ton AC unit that I also replaced. Last July my cooling bill was $95. This July it was $62 with the heat pump running in reverse. The higher SEER2 rating on the new unit (20.5 versus about 13 on the old AC) made a noticeable difference. Across the full year, counting heating savings plus cooling savings minus the increase in my electric base rate from the utility, I'm about $720 ahead.

Cold Weather Performance Below 20F

This was the thing I worried about the most. The short answer is that the heat pump handled it better than I expected, but not perfectly.

Down to about 25F it runs like nothing is wrong. The COP stays above 2.5 and the house holds temperature without any backup. Between 25F and 15F you can feel the system working harder. Run times get longer, and on a couple of nights when it was 18F outside and windy, the indoor temp drifted down from 70 to 67 before it caught back up. It never felt cold, but I noticed it.

Below 15F I had the electric resistance backup kick in three times during the year. Once at 8F in late January, once at 11F during a windchill event, and once at 6F in early February. That backup strip is expensive to run. Those three events probably cost me an extra $35 to $40 combined. If I lived somewhere that saw sub-15F weather regularly for weeks at a time, the math would start to shift.

Defrost cycles are real and a little strange if you've never seen them. The outdoor unit will periodically reverse itself to melt ice off the coils. It sounds like the system is switching to cooling mode for a few minutes, because it basically is. During a defrost cycle, the house doesn't get colder in any way I could measure, but the first time I heard it I went outside to check if something was broken. It runs a defrost maybe every 30 to 90 minutes when it's below 30F and humid. You get used to it.

Comfort and Noise Differences

The gas furnace blasted hot air at about 120F from the vents for 10 or 15 minutes, then shut off and let the house coast until it dropped a couple degrees, then blasted again. You could always tell where you were in the cycle. Near a vent it was almost too warm. Far from one it was cool.

The heat pump runs almost continuously at a lower output. Air comes out of the vents around 90 to 95F, which doesn't feel as warm to the hand, but the house temperature stays within about half a degree all day. I genuinely did not expect this to matter as much as it does. The consistency is better than what the furnace delivered. No hot blasts, no cold gaps.

Noise is a mixed bag. Inside the house it's quieter because the blower runs at a lower speed most of the time. The furnace would ramp up with a noticeable whoosh every cycle. The heat pump's variable speed fan is more of a constant low hum. Outside, though, the heat pump compressor is louder than I anticipated. My old AC condenser was tucked around the side of the house and I never thought about it. The heat pump outdoor unit is noticeably louder, especially in heating mode at low temperatures when the compressor is working hard. My neighbor hasn't said anything, but I think about it. If the unit were near a bedroom window, I'd want a sound blanket or a setback from the wall.

What It Cost to Install

The gas furnace it replaced would have cost about $4,800 to swap for another similar model, based on two quotes I got before deciding to go the heat pump route. One contractor quoted $3,900 and another $5,200, both for a 96 AFUE two-stage unit with installation.

The heat pump system came in at $12,400 all-in. That included the indoor air handler, the outdoor unit, a new line set, the electric backup strip, a new thermostat, and labor. I got the 30% federal tax credit, which brought my out-of-pocket cost down to $8,680. My state had an additional $1,000 rebate through the utility, so the effective price was $7,680.

If I compare that $7,680 to the $4,800 furnace-only replacement, the difference is $2,880. At $720 per year in energy savings, the payback on the incremental cost is about four years. That's not bad. But if I compare the full $7,680 to doing nothing and keeping the old furnace alive for a few more years, the payback stretches to over ten years. The honest framing depends on whether your existing system is due for replacement anyway.

One thing I didn't budget for was the electrical panel upgrade. My panel was full and couldn't accommodate the 40-amp breaker the heat pump needed. That was an extra $1,800 from the electrician. Some houses won't need this. Mine did. Ask your contractor to check before you sign anything.

Would I Do It Again

Yes, but I'd go in with different expectations. The savings are real but not dramatic in a zone 5 climate. The comfort improvement surprised me more than the bill reduction. And the cold weather performance, while solid for 95% of winter, does have limits that gas simply doesn't.

If I were in zone 3 or 4 where temps rarely dip below 20F, the heat pump would be a no-brainer. In zone 6 or 7 with extended stretches below zero, I'd probably keep a gas furnace as primary and add a heat pump as a supplemental system. Zone 5 is right on the edge where it works as a standalone system if you size it correctly and accept a few nights per winter where the backup strips earn their keep.

The thing I'm watching now is time-of-use electricity rates. My utility is rolling out a new rate structure next year that charges more during peak evening hours, which is exactly when heating demand is highest. If the peak rate lands where they're projecting, it could eat into about a third of my annual savings. That's the variable that will determine whether year two looks as good as year one.