If you already have a working gas furnace and decent ductwork, you don’t have to choose between a heat pump and a furnace. You can run both. A dual-fuel system pairs a heat pump with your existing gas furnace and lets a smart thermostat decide which one runs, based on the outdoor temperature.
The result: heat pump efficiency for most of the Fraser Valley heating season, gas furnace headroom for the coldest nights, and full redundancy if either system needs service. For homes already on natural gas, it’s often the lowest-risk way to cut heating costs without ripping out equipment that still works.
This guide covers how dual-fuel works, what the switchover temperature is, who it suits, and what it costs. If you’re still deciding between the two systems in the first place, our heat pump vs. gas furnace comparison covers that. This post is about running both.
How a dual-fuel system works
A dual-fuel setup keeps your existing gas furnace and adds a heat pump to the same duct system. Both share the furnace’s blower and ductwork, so there’s no second set of vents or a separate air handler. Here’s the sequence on a cold morning:
The heat pump runs first. It moves heat from the outside air into your home using electricity, not combustion. This is the efficient mode, and it handles the large majority of the season.
When the outdoor temperature drops below a set point, the thermostat shuts the heat pump off and fires the gas furnace instead.
The furnace produces a burst of hot air through the same ducts until the home is back to setpoint.
As temperatures climb back up, the system returns to the heat pump.
Only one system runs at a time, and the thermostat handles the handoff automatically. The heat pump also becomes your air conditioner in summer, which the furnace could never do. One system, both seasons, plus a gas backup for the worst of winter.
The switchover temperature
The switchover point (sometimes called the balance point or changeover temperature) is the outdoor temperature at which the system stops using the heat pump and starts using the furnace. It’s the single most important setting in a dual-fuel install.
Set it too high and you burn gas you didn’t need to. Set it too low and the heat pump strains on the coldest nights when the furnace would do the job more cheaply. Two factors decide where it lands:
Economics: the temperature at which gas becomes cheaper per unit of heat than electricity, based on your BC Hydro and FortisBC rates and the heat pump’s efficiency at that temperature.
Capacity: the temperature at which the heat pump can no longer keep up with the home’s heat load on its own.
For most Fraser Valley homes, the switchover ends up around -2°C to -7°C, though a cold-climate inverter heat pump rated to -25°C can carry the load far lower if the economics favour it. We dial in the exact number during your Home Energy Assessment, using your real fuel costs and load, not a factory default.
A modern smart thermostat makes this setting easy to manage, and some models adjust the changeover automatically based on live energy pricing.
Who dual-fuel suits
Dual-fuel isn’t for everyone. It makes the most sense when three things are true:
You already have a working gas furnace. If it’s under 10 years old and running well, keeping it as backup means you’re not throwing away good equipment. If it’s at the end of its life, a straight heat pump replacement is usually the cleaner call.
Your ductwork is in good shape. Both systems share the ducts. If the duct system is sound and sized correctly, the retrofit is straightforward.
You’re on natural gas already. The gas line, meter, and venting are in place, so adding a heat pump to the existing furnace is a lower-cost path than a full system swap.
It’s a strong fit for homeowners who want the efficiency and cooling of a heat pump but want the reassurance of gas heat on the handful of nights each winter when temperatures really drop. If those conditions don’t apply, another option usually fits better: a home with no ducts is better served by a ductless setup, and a home coming off oil or baseboards gets more benefit from a full heat pump.
Cost and efficiency
Up front, a dual-fuel install costs more than replacing a furnace on its own, because you’re adding a heat pump to the system. But you’re not paying for a new furnace, and you gain air conditioning you didn’t have before.
The efficiency case is where dual-fuel earns its keep. Across a normal Fraser Valley winter, the heat pump does the heavy lifting:
Outdoor conditions | What runs | Share of the season |
|---|---|---|
Mild to cool (above switchover) | Heat pump | 85–95% |
Cold snaps (below switchover) | Gas furnace | 5–15% |
Because the heat pump handles most of the season at roughly three units of heat per unit of electricity, operating costs come down meaningfully compared to running gas all winter. The furnace only steps in for the small slice of hours when it’s cheaper or necessary. You get most of the savings of a heat pump with none of the worry about the coldest nights.
Heat pumps in the Fraser Valley typically cut heating costs 30 to 50% versus baseboards or oil, and a dual-fuel system captures the bulk of that while keeping gas as a low-cost peak-load tool. Because it uses ENERGY STAR certified, HPSC-eligible equipment, the heat pump side can also qualify for BC rebates. Worth reviewing our BC heat pump rebate guide before you buy, since the paperwork depends on a registered installer.
Redundancy for cold snaps
The quiet advantage of dual-fuel is redundancy. You have two independent heat sources in one system.
If the heat pump ever needs service mid-winter, the furnace carries the home. If gas service is interrupted, the heat pump covers heating down to its rated capacity. For homeowners who remember a hard cold snap and want a fallback, that redundancy is real peace of mind.
It also means the coldest, most demanding nights are handled by the furnace at full output, so the heat pump never has to run flat-out at its efficiency floor. That tends to be easier on the equipment and keeps comfort steady when it matters most.
One honest note: both systems still need electricity to run. The furnace needs power for its blower, ignition, and controls even though it burns gas. If riding out a power outage matters to you, a generator covers either system.
FAQ
What is dual-fuel heating?
Dual-fuel heating pairs a heat pump with a gas furnace on the same duct system. The heat pump handles most of the heating season efficiently, and the furnace takes over automatically when outdoor temperatures drop below a set switchover point. Only one runs at a time, and a smart thermostat manages the handoff.
What temperature should the switchover be set at?
For most Fraser Valley homes it lands somewhere around -2°C to -7°C, but the right number depends on your gas and electricity rates and your home’s heat load. We calculate it during the Home Energy Assessment using your real fuel costs rather than a generic factory setting.
Do I need to keep my old furnace for dual-fuel?
That’s the whole idea. Dual-fuel is designed for homes that already have a working gas furnace in good condition. If your furnace is near the end of its life, a straight heat pump replacement is usually the better value. If it has years left, keeping it as backup makes sense.
Is dual-fuel cheaper to run than a furnace alone?
In most cases, yes. The heat pump carries 85 to 95% of the season at high efficiency, and the furnace only fires on the coldest nights. That mix typically costs less to operate than running gas all winter, while still giving you gas headroom when you need it.
Does a dual-fuel heat pump also provide air conditioning?
Yes. The heat pump reverses in summer to cool your home, so a dual-fuel system gives you central air conditioning that a furnace alone never could. One system covers heating, cooling, and gas backup.
Can a dual-fuel system qualify for BC rebates?
The heat pump portion can, provided it uses eligible ENERGY STAR equipment installed by an HPSC-registered contractor. As a registered installer, we handle the rebate paperwork as part of the job. See our rebate guide for the current stack of programs and amounts.
Cohesive Mechanical is the Fraser Valley’s trusted HVAC and plumbing experts - based in Chilliwack, serving Abbotsford, Langley, and the Lower Mainland since 2017. Done right the first time. Clean installs. Clear communication.
Not sure if dual-fuel is right for your home? Book a free quote and we’ll run the numbers during a no-charge Home Energy Assessment. Learn more about our heat pump installations or furnace repair and replacement.
Related: Heat Pump vs. Gas Furnace: Which Is Right for Your Fraser Valley Home? and Smart Thermostats: Getting the Most From Your Heat Pump
