As energy codes tighten and environmental pressures push electrification to the forefront, homeowners and builders in all regions face a conundrum: how to adopt efficient electric heating without sacrificing comfort or reliability during cold weather. A growing number of HVAC professionals are finding an answer in dual-fuel solutions—pairing electric heat pumps with propane-fueled furnaces or boilers. The result is a system that offers the efficiency of a heat pump during milder seasons and the dependable, on-demand warmth of propane when temperatures plunge.

How Dual-Fuel Systems Work

At the heart of these systems is an electric air-source heat pump, which extracts ambient heat from outdoor air—even in cooler weather—and transfers it indoors either through forced air or hydronic tubing. But when outdoor temperatures drop too low for the heat pump to operate efficiently, the system seamlessly switches to a propane-powered furnace or boiler. In most setups, this changeover happens around 30°F, though performance can vary depending on the brand and efficiency of the heat pump.

“A lot of the high-end heat pumps claim to operate down to -13°F,” says Moose Harte, manager of residential construction services at Eastern Propane. “But what they don’t always tell you is that you may only be getting about 30% of maximum heat capacity at those temperatures. It’s not enough when you really need it.”

The Air-to-Water Method

While most dual-fuel applications rely on air-to-air heat distribution, there's rising interest in air-to-water systems, which provide an effective solution for homes with existing or planned hydronic heating systems. In an air-to-water setup, the heat pump extracts ambient heat from the outside air and transfers it into water, which is then circulated through in-floor radiant tubing, baseboard radiators, or even wall and ceiling panels. This method offers quiet, even, and draft-free heat distribution, which many homeowners find more comfortable than forced air.

When outside temperatures fall below the threshold where the heat pump can perform efficiently—often between 30°Fand 40°F—a propane boiler takes over, ensuring the home stays warm. These systems are especially valuable in regions where extended periods of freezing weather are common.

“The air-to-water method is a smart fit for homes with existing hydronic infrastructure,” says Ryan Klopfenstein, technical trainer at Eastern Propane. “It allows homeowners to take advantage of electric efficiency during moderate weather while still benefiting from the high heat output and reliability of propane when it really counts.”

Propane boilers used in these configurations typically maintain high efficiency—often between 95 and 98%—regardless of the outside temperature. This consistency and high output temperatures, combined with their ability to integrate seamlessly with radiant heating technology, makes them a key component of a robust and flexible dual-fuel system.

Why Dual-Fuel Makes Sense in Cold Climates

In areas like the Northeast, where winters are long and power outages are a concern, propane offers critical advantages. “If you lose power, running an electric heat pump requires a large generator,” Klopfenstein says. “But propane systems need far less electrical supply. A small generator can keep you warm.”

Harte adds that last winter served as a reality check for many homeowners who had gone all-electric. “We finally had a real winter. We got call after call from people whose mini-splits couldn’t keep up. Some homes never got above 50°F, and their electric bills were through the roof.”

While utilities continue to incentivize electric heat pump installations, industry professionals warn of potential consequences. “Nobody’s talking about the strain on the grid,” Harte says. “All-electric systems may look good on paper, but they’re not always practical—or affordable—in the field.”

Builder Concerns and Installation Strategies

Builders are paying attention. “For most, it comes down to cost,” Harte says. “We’re showing them that dual-fuel isn’t just reliable—it’s competitive, especially when you factor in propane for hot water, cooking, fireplaces, and even standby generators.”

One common strategy for new builds includes mini-split heat pumps for upper floors and conventional propane systems for the main floor. This hybrid approach reduces ductwork and labor costs while ensuring comfort and backup.

Another consideration is electrical infrastructure. “If you're installing all-electric systems, you may need to upgrade your electrical panel,” Klopfenstein says. “With propane, you can often avoid those costs entirely.”

Beyond the Furnace: Total Energy Integration

Introducing propane into a home doesn't just support heating—it opens doors to other applications. “Once you have propane on site, you can use it for water heating, which is often more cost-effective than electric,” Klopfenstein says. “You can cook with it, install a fireplace, and add a generator. It gives you options—and peace of mind.”

In the race toward energy efficiency and electrification, dual-fuel HVAC systems stand out as a pragmatic bridge between sustainability and reliability. For homeowners in cold climates, combining an air-source heat pump with a propane backup ensures comfort, reduces long-term energy costs, and preserves flexibility—even in the depths of winter.

“Heat pumps have their place, especially in shoulder seasons,” Klopfenstein says. “But when it gets really cold, you’ll be glad you have propane.”

Learn more about how builders are incorporating clean, energy-efficient propane into their projects.