Definition: heat pump vs furnace at a glance
A furnace burns fuel (natural gas, propane, or fuel oil) to create heat. A flame heats a metal heat exchanger; a blower pushes air across that exchanger; warm air goes into your ductwork. Modern furnaces are 90–98% AFUE, meaning 90–98% of the fuel's energy becomes heat in your house.
A heat pump doesn't burn anything. It's the same refrigerant cycle as an air conditioner — it moves heat from one place to another — just reversible. In cooling mode, it pumps heat out of your house. In heating mode, it pumps heat into your house from outdoor air. Even at 5°F outdoor temp, there is heat in the air; the heat pump just concentrates it.
Cold-climate (CCHP) heat pumps from York, Mitsubishi, Bosch, and Trane now operate down to -13°F to -20°F and still deliver useful capacity. Five years ago this conversation was different.
When the heat pump wins in Wisconsin
- You're replacing AC and heating at the same time. A heat pump does both jobs in one box. If your furnace is dying and your AC is the same age, the heat pump premium is small compared to two separate replacements.
- Your electric rate is reasonable and your propane is high. Most of Walworth and rural Waukesha is propane country. We Energies and Alliant electricity at ~[verify: current 14–17¢/kWh residential rate] typically beats propane heating cost-per-BTU for the cold-climate models operating down to about 10°F.
- You have Focus on Energy + federal incentives lined up. Heat pumps qualify for the 25C federal credit (up to [verify: $2,000/year]), Focus on Energy rebates, and (for income-eligible) Inflation Reduction Act HEEHRA point-of-sale rebates. Stacked, the incentive picture is currently better than for furnaces.
- You care about indoor air quality and humidity control. A variable-speed heat pump runs longer at lower stages, which dehumidifies better in summer and gives more even temperatures in winter than a single-stage furnace.
When the furnace still wins
- You heat with natural gas. Below about 10°F — which happens 40–60 hours per winter in southeast Wisconsin — even a cold-climate heat pump's cost-per-BTU loses to a 95% AFUE gas furnace. If you have city gas, the pure-furnace economics still win for sustained deep cold.
- Your electrical service is limited. A heat pump on backup resistance heat can pull 60+ amps. Older Lake Country cabins with 100-amp service often need a panel upgrade to support it. That's not a deal-breaker — we do panel upgrades routinely — but it adds to the project.
- You want the fastest temperature recovery on a cold morning. A furnace at full burn delivers 90°F+ supply air. A heat pump delivers 90–100°F supply — comfortable but not "blast of hot air" warm. Some homeowners prefer the furnace feel; that's a real preference, not wrong.
Failure modes: the hybrid trap
The "dual-fuel" hybrid — a heat pump plus a gas furnace, switching at a crossover temperature — is genuinely the right answer for many southeast Wisconsin homes. But it has two common failure modes:
- Wrong crossover setpoint. The installer sets the changeover at 35°F because that was the default ten years ago — back when heat pumps lost efficiency fast. A modern cold-climate heat pump should switch over at 15–25°F depending on the specific unit and your utility rates. We re-program these on takeover jobs constantly.
- Two systems, one bad install. A hybrid has a heat pump, a furnace, a single thermostat, two refrigerant lines, and a complicated control sequence. If it's not commissioned correctly, you'll be running auxiliary resistance heat on mild days and never know. The commissioning report is what separates a good hybrid install from a bad one.
Proof: how we choose, with numbers
On a typical 2,400 sq ft East Troy home with propane heat (~$1,800–$2,400 annual heating cost) and a 14-SEER AC (8 years old), the swap math usually goes:
- Pure cold-climate heat pump: [verify: $11–$16k installed before incentives]. Operating cost ~[verify: 40–55% of prior propane bill on a 15-year lifecycle]. Loses some efficiency on the coldest 60–80 hours per winter.
- Dual-fuel hybrid (heat pump + 95% propane furnace): [verify: $13–$19k installed]. Best operating cost in nearly every Wisconsin winter we model. Most complex install — needs a great commissioning.
- Straight 95% propane furnace + new AC: [verify: $9–$14k installed]. Lowest up-front; highest operating cost; lowest incentive stack.
Action: get the right system, not just "a new system"
- Request an in-home heat-loss calculation. A Manual-J load calc is the right starting point — not a square-foot rule of thumb. We do this on every quote.
- Already have a quote? Bring it. Our Free Second Opinion is apples-to-apples — same equipment specs, same warranty, same scope of work.
- Read the rebate guide before you commit — the incentive picture matters more than ever right now.
