What are Dual-Fuel HVAC Systems? Are They Worth It?
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Author
Andrew Blok
Electrification and Solar Writer and Editor
Heat pumps are highly efficient heating and cooling machines that perform reliably in even the coldest climates. Heat pumps are widely installed and performing well in frigid places like Scandinavian countries and the state of Maine.
Still, some people switch to heat pumps in steps, installing one alongside an existing gas furnace. What are the pros and cons of installing a dual-fuel HVAC system like that. And is it necessary, or are heat pumps too good to need the backup?
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What is a dual-fuel HVAC system and how does it work?
A dual-fuel system (sometimes called a hybrid heat system) consists of two main components:
- An electric air-source heat pump: This sits outside and handles both cooling in the summer and heating during mild-to-cold weather.
- A natural gas or propane furnace: This sits inside and takes over when temperatures drop below the heat pump's optimal efficiency range.
How it works
The system typically uses an economic balance point — a specific outdoor temperature (depending on your heat pump and electricity rate) programmed into your thermostat. The idea is that you’ll use the heat pump when it’s cheaper to run and switch to the furnace when it’s cheaper to run.
- Above the balance point: The heat pump is incredibly efficient. It doesn't create heat; it moves it from the outside air into your home.
- Below the balance point: Because some heat pumps can get less efficient as it gets colder outside, they may be more expensive to run. When this temperature is reached, your gas furnace can fire up.
As heat pumps get more efficient, this type of dual-fuel system may become less valuable. As the temperature at which it’s cheaper to run a gas furnace gets lower and lower, there may be fewer instances where it’s worth maintaining two systems.
Pros and cons of dual-fuel systems
| Pros | Cons |
|---|---|
| Extremely high efficiency in moderate temperatures (200%-400% that of a gas furnace or electric resistance heating). | Lower efficiency once the gas furnace takes over. |
| Can lower monthly utility bills by using the cheapest fuel source available. | Higher upfront installation cost compared to a single unit, and multiple machines. |
| Heat pump delivers best in class comfort. | Requires maintenance for two different types of systems. |
| Reduces carbon footprint by using electricity for the majority of the year. | Still relies on fossil fuels for peak winter heating. |
| Heat pump portion can be powered by rooftop solar panels. | You must buy gas, oil, or propane. |
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Should you get a dual-fuel HVAC system?
The value proposition of a dual-fuel system is based on two ideas: that heat pumps may not keep up with frigid temperatures and the ability to switch between fuels allows you to opt for either when that system is cheapest to run.
According to the U.S. Department of Energy, heat pumps can reduce electric bills for most Americans, and trim electricity use for heating by approximately 50% compared to electric resistance heating like baseboard heaters. And, 13 million homes that use natural gas for heat could also save by switching.
The specifics of a location’s gas and electricity prices, paired with its climate, will determine how much it costs to heat your home with each fuel, but research shows that most Americans can save with a wholesale switch. A dual-fuel system will also have higher maintenance costs, since it includes two distinct systems, each with their own service and repair needs.
Modern cold-climate heat pumps are capable of heating homes in frigid temperatures. While older models struggled to keep up with frigid temperatures, that's not the case anymore, according to sources like the state of Maine, where heat pump installations have outpaced adoption goals. It says that “properly sized heat pumps can be used to heat virtually any home or business.”
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Frequently asked questions
Is a dual-fuel system more expensive to install?
Yes. You are essentially paying for two pieces of equipment (a heat pump and a furnace), though many are installed when people add a highly efficient heat pump to an existing furnace system.
Do I need a special thermostat?
Yes. You need a "dual-fuel compatible" smart thermostat that can communicate with both the outdoor unit and the indoor furnace to manage the switch-over point automatically. Many smart thermostats have this capability.
How long do these systems last?
Typically, the furnace can last 15–20 years, while the heat pump (which works year-round for both heating and cooling) lasts about 10–15 years. Regular maintenance is key to longevity.
Disclaimer: This content is for educational purposes only. Palmetto does not provide tax, legal, or accounting advice. Please consult your own tax, legal, and accounting advisors.
