Best Dual Fuel Heat Pumps in the USA: 7 Systems Compared

It is a complete heating strategy that combines two different technologies: an electric heat pump and a combustion furnace. The heat pump can provide both cooling and heating, while the furnace provides a second source of heat when the control system determines that furnace operation is appropriate.

That arrangement can be particularly useful in American homes that already have forced-air ductwork and a gas furnace. Instead of replacing an aging central air conditioner with another air conditioner, a homeowner can potentially install a heat pump and retain the furnace as the second heating source.

Carrier describes dual fuel as a system that combines an electric heat pump with a gas furnace and automatically alternates between them according to conditions. Trane similarly describes a dual-fuel system as a heat pump plus furnace, with the heat pump normally providing heating before the furnace takes over under colder conditions. Carrier’s dual-fuel explanation and Trane’s technical explanation both emphasize automatic changeover between the two heat sources.

The important question is therefore not simply, “Which heat pump is most efficient?”

The better question is:

Which heat pump, furnace and control combination makes sense for this particular house, climate, fuel prices and heating load?

This guide examines seven current heat-pump options that can be incorporated into dual-fuel configurations, including variable-speed split systems and packaged dual-fuel equipment.

Quick Comparison: 7 Dual Fuel Heat Pump Options

Important: The efficiency figures above are manufacturer-published maximum ratings and can depend on the exact indoor coil, furnace, blower, controls, region and AHRI-rated combination. They should not be interpreted as the efficiency of every possible installation.

What Is a Dual Fuel Heat Pump?

A dual fuel system combines two heating sources:

1. An electric heat pump that transfers heat between the outdoors and the house.
2. A combustion furnace that burns natural gas, propane or another approved fuel to produce heat.

The heat pump also provides air conditioning during summer.

During moderate weather, the heat pump can provide heating without operating the furnace. When outdoor conditions become colder, or when the selected control strategy determines that furnace operation is preferable, the system changes heating sources.

Why Install a Heat Pump If You Already Have a Gas Furnace?

This is the fundamental reason dual-fuel systems exist.

A furnace is very effective at producing heat, but it can only heat. A heat pump can heat and cool using the same refrigeration system.

Replacing an aging central air conditioner with a heat pump can therefore add electric heating capability without removing the furnace.

The homeowner effectively gets:

• Heat-pump cooling
• Heat-pump heating
• Gas-furnace heating
• Automatic switching between heating sources
• A second heating source for very cold conditions

Carrier specifically notes that dual-fuel systems can use the heat pump for much of the heating season and switch to the furnace when conditions make furnace operation preferable.

How Does the System Decide Which Heat Source to Use?

The changeover can be based on temperature, heating capacity, system configuration and economic considerations.

One important temperature is the balance point.

However, the word balance point can describe two related but different concepts.

Thermal Balance Point

The thermal balance point concerns the relationship between:

• Heat loss from the house
• Heating capacity of the heat pump

Suppose a house loses 45,000 BTU/h at a particular outdoor temperature while the heat pump can provide 40,000 BTU/h at that condition.

The heat pump cannot independently satisfy the entire load.

The furnace can therefore become necessary.

Economic Balance Point

The economic balance point is different.

A heat pump might still technically be capable of heating the house, but the furnace could be less expensive to operate depending on:

• Electricity price
• Natural gas price
• Heat-pump COP
• Furnace AFUE
• Outdoor temperature
• Heat demand

Consequently, there is no universal “switch to gas at 35°F” rule that applies to every American home.

Important Heat Pump Ratings

SEER2

SEER2 describes seasonal cooling efficiency.

It is useful for comparing cooling performance but should not be used as the sole basis for selecting a dual-fuel system.

HSPF2

HSPF2 describes seasonal heating efficiency for heat pumps.

It provides a seasonal comparison but does not tell you exactly how much heating capacity the heat pump will deliver at a particular very low temperature.

COP

COP is especially useful for cold-weather analysis.

A COP of 2.0 means that the heat pump is delivering approximately two units of heat for every unit of electrical energy consumed at the specified test condition.

AFUE

AFUE applies to the furnace rather than the heat pump.

A high-AFUE condensing furnace can convert a large percentage of its fuel input into useful heating output under the standardized rating procedure.

In a dual-fuel system, therefore, the homeowner should examine both heat-pump heating efficiency and furnace AFUE.

1. Carrier Infinity 23 27VNA3 — Best Premium Variable-Speed Dual Fuel Option

Product Description and Best Use Case

The Carrier Infinity 23 27VNA3 is a premium variable-speed heat pump designed for high-efficiency heating and cooling.

Carrier lists the 27VNA3 at up to 23 SEER2 and up to 10.5 HSPF2, with heating operation down to -13°F. Carrier also identifies it as its highest-efficiency heat-pump option within its dual-fuel portfolio.

Best use: A premium ducted dual-fuel system where variable-speed operation, advanced controls and low-temperature heat-pump performance are important.

Why We Selected It

• Variable-speed compressor
• Up to 23 SEER2
• Up to 10.5 HSPF2
• Heating operation down to -13°F according to Carrier
• Infinity communicating controls
• Advanced humidity control
• Quiet operation
• Suitable for integration with compatible Carrier furnace equipment

A variable-speed compressor can reduce the need for repeated full-capacity cycling by adjusting output according to demand.

That characteristic can be particularly useful in a dual-fuel system because the heat pump may be used for a large portion of the heating season rather than only as an occasional backup source.

Relevant Certification / Standards

Carrier identifies the 27VNA3 as ENERGY STAR qualified. Exact certification and efficiency should be verified for the complete AHRI-rated system combination selected for the installation.

Important Limitations

• Premium equipment generally costs more to install.
• Communicating controls can increase system complexity.
• Actual efficiency depends on the matched indoor equipment.
• Correct commissioning is important.
• Not every old furnace is automatically compatible.

Who Should Buy

• Homeowners seeking a premium variable-speed system
• Homes with existing gas furnace infrastructure
• Cold or mixed climates
• Homeowners who want sophisticated system controls
• People replacing an aging central AC with heat-pump capability

Who Shouldn’t Buy

• Homeowners focused entirely on minimum initial cost
• Homes without suitable ductwork
• Projects without access to a qualified communicating-system installer
• Homes where a simpler heat-pump/furnace combination would meet the load adequately

2. Carrier Performance 27TPA8 — Best Two-Stage Carrier Dual Fuel Option

Product Description and Best Use Case

The Carrier Performance 27TPA8 is a two-stage heat pump designed as a less complex alternative to the company’s premium variable-speed equipment.

Carrier lists the model at up to 18.5 SEER2 and describes it as using InteliSense technology. Carrier includes the 27TPA8 within its dual-fuel heat-pump portfolio.

Best use: Homeowners who want staged heat-pump operation and dual-fuel capability without moving all the way to Carrier’s premium Infinity platform.

Why We Selected It

• Two-stage operation
• Up to 18.5 SEER2
• InteliSense technology
• Compatible with appropriate Carrier furnace systems
• Useful middle ground between single-stage and variable-speed equipment

Two-stage equipment can spend more time operating at lower output than a conventional single-stage system, depending on load and controls.

This can improve temperature stability and reduce the abrupt full-capacity cycling associated with basic single-stage systems.

Relevant Certification / Standards

Verify ENERGY STAR qualification and AHRI certification for the exact heat-pump/furnace/coil combination quoted by the contractor.

Important Limitations

• Not as continuously modulating as a variable-speed system.
• Published efficiency is dependent on system combination.
• Control compatibility must be verified.
• Cold-weather capacity should be checked rather than inferred from SEER2.

Who Should Buy

• Homeowners wanting staged operation
• Existing Carrier furnace owners
• Mixed-climate homes
• Homeowners who want more sophistication than single-stage equipment

Who Shouldn’t Buy

• Those wanting maximum variable-capacity modulation
• Homes without ductwork
• Projects where basic equipment is sufficient and controls are the priority

3. Carrier Comfort 27SCA5 — Best Simple Carrier Dual Fuel Option

Product Description and Best Use Case

The Carrier Comfort 27SCA5 is a simpler single-stage heat-pump option. Carrier lists it at up to 16 SEER2 and includes it among the heat pumps available for Carrier dual-fuel applications.

Best use: A homeowner who wants the basic dual-fuel concept without paying for a premium variable-speed compressor.

Why We Selected It

• Single-stage compressor
• Up to 16 SEER2
• Simpler system architecture
• Can be combined with a compatible furnace
• Potentially lower equipment complexity than premium communicating equipment

Its main attraction is not maximum efficiency. It is simplicity.

In some homes, a straightforward heat pump paired with a properly sized furnace can provide the desired dual-fuel function without the need for a highly sophisticated variable-speed system.

Relevant Certification / Standards

Verify the current ENERGY STAR and AHRI status of the exact combination before purchase.

Important Limitations

• Single-stage operation provides less modulation than premium systems.
• Efficiency is lower than Carrier’s premium models.
• Comfort and humidity performance can depend more strongly on sizing.
• Low-temperature capacity should be examined separately.

Who Should Buy

• Budget-conscious homeowners
• Moderate-climate homes
• Existing Carrier furnace owners
• Owners prioritizing simpler equipment

Who Shouldn’t Buy

• Very cold-climate homeowners seeking maximum heat-pump capacity
• People specifically seeking variable-speed operation
• Homeowners prioritizing the highest available seasonal efficiency

4. Lennox SL25XPV — Best Premium Lennox Variable-Capacity Dual Fuel Option

Product Description and Best Use Case

The Lennox SL25XPV is a variable-capacity heat pump in the Dave Lennox Signature Collection.

Lennox currently lists the SL25XPV at up to 23 SEER2 and 10.3 HSPF2, with configurations from 2 to 5 tons. Lennox identifies it as ENERGY STAR qualified.

Best use: A premium Lennox dual-fuel system where variable-capacity operation and communicating controls are desired.

Why We Selected It

• Variable-capacity compressor
• Up to 23 SEER2
• Up to 10.3 HSPF2
• 2–5 ton configurations
• Precise Comfort technology
• S40 Smart Wi-Fi communicating thermostat requirement in published documentation
• Dave Lennox Signature Collection platform

Lennox’s published technical documentation identifies variable capacity as a key characteristic and lists cooling capacities from approximately 22,000 to 56,000 BTU/h depending on the model.

Relevant Certification / Standards

Lennox identifies the SL25XPV as ENERGY STAR qualified. Exact certification depends on the qualifying system combination.

Important Limitations

• Requires careful equipment matching.
• Communicating controls add complexity.
• Premium equipment has a higher initial cost.
• Installation quality has a major effect on actual performance.
• Do not select the system solely on its 23 SEER2 headline.

Who Should Buy

• Homeowners seeking variable-capacity operation
• Lennox system owners
• Homeowners wanting integrated communicating controls
• Homes where precise part-load operation is valuable

Who Shouldn’t Buy

• Owners seeking the simplest possible HVAC system
• Projects where Lennox communicating controls are unavailable locally
• Homeowners focused primarily on minimum installation cost

5. Trane 20 TruComfort Variable Speed Heat Pump — Best High-Performance Trane Option

Product Description and Best Use Case

Trane’s current 20 TruComfort variable-speed heat-pump platform is designed for high-efficiency operation and can be integrated into a hybrid heating arrangement with a compatible Trane furnace.

Trane’s current comparison information lists the 20 TruComfort variable-speed heat pump at up to 22.4 SEER2 and 10.5 HSPF2, with 100% heating capacity down to 32°F and 70% heating capacity down to 5°F in the listed configuration.

Best use: Mixed and colder climates where maintaining useful heat-pump capacity at lower temperatures is important.

Why We Selected It

• Variable-speed operation
• Up to 22.4 SEER2 in the listed current configuration
• Up to 10.5 HSPF2
• Published low-temperature capacity information
• Trane Link communicating technology on applicable systems
• Can be integrated with compatible Trane furnaces for hybrid heating

Trane explicitly states that its furnaces can be paired with heat pumps in hybrid heating systems.

Relevant Certification / Standards

Trane lists qualifying heat-pump configurations as ENERGY STAR qualified. Exact ratings depend on the indoor unit and system combination.

Important Limitations

• Actual efficiency depends on the matched indoor equipment.
• Variable-speed communicating equipment can be more expensive.
• Low-temperature capacity should be evaluated against the home’s design heating load.
• Trane Link-compatible equipment may require appropriate controls.

Who Should Buy

• Homeowners in mixed or colder climates
• People wanting variable-speed operation
• Existing Trane furnace owners
• Homes where low-temperature heat-pump capacity matters

Who Shouldn’t Buy

• Homeowners looking only for a basic replacement
• Projects where premium controls are unnecessary
• Homes where the local contractor lacks experience with the communicating platform

6. American Standard AccuComfort Platinum 20 — Best American Standard Variable-Speed Dual Fuel Option

Product Description and Best Use Case

The American Standard AccuComfort Platinum 20 is a communicating variable-speed heat pump designed to adjust output according to the home’s heating and cooling demand.

American Standard’s current product page lists up to 22.4 SEER2 and up to 10.5 HSPF2, with variable fan operation and ENERGY STAR qualification when the appropriate coil components are used.

The manufacturer also describes the current R-454B version as using variable-speed operation and AccuLink communicating technology.

Best use: A premium American Standard dual-fuel system where variable-speed operation and communicating equipment are desired.

Why We Selected It

• Variable-speed operation
• Up to 22.4 SEER2
• Up to 10.5 HSPF2
• AccuLink communicating technology
• Variable fan operation
• ENERGY STAR qualified when paired with appropriate components
• Current R-454B version available

American Standard also states that the system can improve heating capacity by as much as 20% under its AccuComfort technology, although actual performance depends on the system configuration.

Relevant Certification / Standards

American Standard identifies the product as ENERGY STAR qualified when the appropriate coil components are used.

As with all split systems, verify the exact AHRI-rated combination rather than assuming that the outdoor unit’s maximum rating applies to every furnace combination.

Important Limitations

• Requires suitable communicating equipment for full system functionality.
• Premium equipment costs more than basic single-stage systems.
• Published maximum ratings are combination dependent.
• Installer familiarity with the communicating platform is important.

Who Should Buy

• Homeowners seeking variable-speed comfort
• People replacing an older American Standard system
• Mixed-climate homes
• Homeowners interested in current low-GWP refrigerant equipment

Who Shouldn’t Buy

• Homeowners seeking minimum upfront cost
• Projects where basic single-stage equipment is sufficient
• Installations without an experienced American Standard dealer

7. Bosch IDS Ultra — Best Cold-Climate Heat Pump for a Dual-Fuel Configuration

Product Description and Best Use Case

The Bosch IDS Ultra is an inverter ducted split heat pump designed specifically for high-performance heating in cold conditions.

Bosch lists up to 19 SEER2 and 10 HSPF2, with up to 100% heating capacity down to 5°F at a COP of 2.1. Bosch also states that the IDS Ultra passed the U.S. Department of Energy Residential Cold Climate Heat Pump Challenge and uses R-454B refrigerant.

Although it can operate as an all-electric heat pump, Bosch specifically confirms that its IDS equipment can be paired with a compatible Bosch gas furnace for a dual-fuel application.

Best use: Cold-climate homes where the homeowner wants a high-performing inverter heat pump while retaining a gas furnace as a secondary heating source.

Why We Selected It

• Inverter-driven compressor
• Up to 19 SEER2
• Up to 10 HSPF2
• 100% heating capacity at 5°F in the published configuration
• COP of 2.1 at 5°F in the published specification
• DOE Residential Cold Climate Heat Pump Challenge qualification
• R-454B refrigerant
• Designed for ducted split applications

This is particularly interesting for dual fuel because the homeowner does not necessarily need to abandon heat-pump operation as temperatures fall.

The heat pump itself is designed for significant cold-weather operation, while the furnace remains available as a second heating source.

Relevant Certification / Standards

Bosch states that the IDS Ultra passed the DOE Residential Cold Climate Heat Pump Challenge. Bosch also lists AHRI and ETL certification for associated IDS Ultra indoor equipment.

Exact system certification should be checked for the complete heat-pump, indoor coil, furnace and control combination.

Important Limitations

• 19 SEER2 is below the maximum headline ratings of some premium competitors.
• Cold-climate performance does not mean the system is automatically suitable for every house.
• Correct sizing remains essential.
• The furnace must be correctly matched for dual-fuel operation.
• Installation and control configuration matter significantly.

Who Should Buy

• Homeowners in cold climates
• People wanting substantial heat-pump operation below freezing
• Homes with compatible Bosch furnace infrastructure
• Homeowners wanting an inverter ducted system
• Projects where low-temperature heat-pump capacity is a major concern

Who Shouldn’t Buy

• Homes in which a simple conventional system is adequate
• Homeowners without access to a qualified Bosch installer
• Projects where an existing furnace cannot be appropriately matched

Understanding the Seven Options

What About Packaged Dual Fuel Heat Pumps?

The seven systems above are primarily heat pumps that can form part of a split-system dual-fuel installation.

There is another architecture: the packaged dual-fuel heat pump.

In a packaged system, the heat pump and gas furnace are integrated into one outdoor cabinet.

Trane’s EarthWise Hybrid Dual Fuel system, for example, combines the heat pump and gas furnace in one packaged cabinet.

Rheem’s Endeavor RDFXYC is another packaged dual-fuel system. Rheem describes it as a single-unit system combining an electric heat pump with a gas furnace and automatic switching between heating sources. Its published documentation also describes two-stage operation at 67% and 100% and states that the system provides substantially more heating capacity than a standard heat pump under its stated conditions.

Packaged systems can therefore be highly relevant when the home’s HVAC architecture is already designed around outdoor packaged equipment.

Split Dual Fuel vs Packaged Dual Fuel

Heat Pump Capacity Is More Important Than Tonnage Alone

A homeowner should not select a dual-fuel heat pump simply because the old air conditioner was a particular size.

A two-ton, three-ton or four-ton label does not tell you whether the system is properly sized for winter heating.

The important calculation is the home’s actual design heating load.

That depends on:

• Building size
• Insulation
• Window area
• Air leakage
• Ceiling height
• Outdoor design temperature
• Indoor design temperature
• Duct losses
• Building orientation
• Internal heat gains

A professional HVAC contractor should perform a load calculation rather than simply matching the new heat pump to the old equipment.

Why Oversizing Can Hurt a Dual-Fuel System

Oversizing is often treated as harmless because the furnace can always provide more heat than necessary.

That assumption can create comfort problems.

An oversized heat pump can:

• Cycle more frequently
• Reduce effective dehumidification
• Create larger temperature swings
• Increase equipment cost
• Operate away from its most efficient part-load range

Variable-capacity systems can reduce some of these problems because they can modulate their output, but proper load calculation remains important.

How Furnace AFUE Fits Into Dual Fuel

The furnace should be evaluated separately from the heat pump.

For example, consider two hypothetical furnaces:

The higher AFUE furnace converts a larger fraction of its fuel input into useful heat under the rating procedure.

But that does not automatically mean that it should run instead of the heat pump at every outdoor temperature.

The operating cost still depends on energy prices and the heat pump’s COP at the current conditions.

Calculating the Economic Balance Point

A simplified comparison can be made using the heat pump’s COP and the furnace’s AFUE.

For a heat pump:

Heat delivered = Electrical energy × COP

For a furnace:

Useful heat = Fuel energy × AFUE

Suppose a heat pump has a COP of 2.5.

It delivers approximately 2.5 units of heat per unit of electrical energy consumed under that particular condition.

If the furnace has a 95% AFUE rating, approximately 0.95 units of useful heat result from each unit of fuel energy under the standardized annual rating methodology.

To determine which source costs less, the homeowner needs the actual electricity and fuel rates.

This is why two identical houses in different states can have different economically sensible changeover points.

Dual Fuel Does Not Automatically Mean the Furnace Runs Below Freezing

This is a common misconception.

Some heat pumps can continue operating effectively well below freezing.

Trane’s current information, for example, lists substantial heating capacity at 5°F for its 20 TruComfort variable-speed system. Bosch’s IDS Ultra is specified for 100% heating capacity at 5°F in its listed configuration.

Therefore, a modern dual-fuel system may continue using the heat pump at temperatures where an older conventional heat pump might have relied heavily on backup heat.

Cold Climate Heat Pump vs Dual Fuel Heat Pump

These terms should not be confused.

A cold-climate heat pump does not inherently require a furnace.

Likewise, a dual-fuel system does not automatically qualify as a cold-climate heat-pump system.

ENERGY STAR’s current cold-climate criteria include low-temperature performance requirements such as a COP of at least 1.75 at 5°F and a heating-capacity requirement at 5°F for qualifying ducted split systems.

What Happens During Defrost?

Air-source heat pumps can accumulate frost on the outdoor coil when operating in heating mode under suitable temperature and humidity conditions.

The system periodically enters a defrost cycle to remove that frost.

During defrost, the heat pump temporarily changes its refrigeration operation.

Depending on the system and control configuration, the indoor furnace or supplemental heating source can help maintain indoor comfort.

This is another reason why dual-fuel controls must be configured correctly.

Why the Thermostat Matters

The thermostat is not simply an on/off temperature switch in a sophisticated dual-fuel system.

It can coordinate:

• Heat-pump operation
• Furnace operation
• Outdoor temperature information
• Heating stages
• Changeover settings
• Emergency heat
• System alarms
• Humidity control

Some premium manufacturers use communicating controls that allow the thermostat and HVAC equipment to exchange considerably more information than a basic conventional thermostat.

This is why replacing a communicating thermostat with a generic thermostat can potentially eliminate some system functionality.

What Is the Best Changeover Temperature?

There is no universal answer.

A practical changeover calculation should consider:

Installation Checklist

1. Perform a Manual J load calculation.
2. Determine the home’s heating design temperature.
3. Determine the home’s cooling design load.
4. Inspect existing ductwork.
5. Inspect the existing furnace.
6. Determine whether the furnace should be retained or replaced.
7. Select the heat-pump capacity.
8. Check heating capacity at low outdoor temperatures.
9. Verify furnace capacity.
10. Verify indoor coil compatibility.
11. Verify thermostat/control compatibility.
12. Obtain the AHRI-rated combination.
13. Determine the changeover strategy.
14. Check electrical requirements.
15. Check gas or propane requirements.
16. Commission the entire system after installation.

What Should Be Included in the Contractor Quote?

A good quote should identify the actual equipment rather than simply saying “high-efficiency dual fuel.”

Ask for:

• Outdoor heat-pump model number
• Indoor coil model number
• Furnace model number
• Thermostat/control model
• AHRI reference number
• Rated SEER2
• Rated HSPF2
• Furnace AFUE
• Heating capacity at design temperature
• Electrical requirements
• Gas requirements
• Warranty terms
• Installation labor
• Permits
• Startup and commissioning procedure

Common Dual-Fuel Buying Mistakes

1. Choosing Only by SEER2

SEER2 is a cooling-season metric. Dual-fuel homeowners also need to examine heating performance.

2. Assuming the Heat Pump Stops Working at Freezing

Modern heat pumps can operate at substantially lower temperatures.

3. Assuming All Furnaces Are Compatible

The complete system must be approved and properly matched.

4. Using the Old AC Size as the New Heat-Pump Size

The correct size should come from the building load.

5. Ignoring Electricity and Gas Prices

The economic changeover point depends partly on local energy rates.

6. Installing Premium Equipment With Poor Ductwork

A sophisticated heat pump cannot compensate for severely defective ductwork.

7. Ignoring the Furnace’s Age

If the existing furnace is already near the end of its useful service life, installing a new heat pump around it may only postpone the furnace replacement decision.

Maintenance of a Dual Fuel System

Heat Pump

• Clean or replace filters.
• Keep the outdoor coil clear.
• Inspect refrigerant circuit.
• Check electrical connections.
• Inspect condensate drainage.
• Verify defrost operation.

Furnace

• Inspect burners.
• Inspect heat exchanger.
• Check ignition system.
• Inspect blower.
• Check gas pressure.
• Inspect venting.

Controls

• Check outdoor temperature sensor.
• Verify changeover operation.
• Verify furnace staging.
• Verify heat-pump staging.
• Check thermostat communication.

Frequently Asked Questions

What is a dual-fuel heat pump?

A dual-fuel heat pump system combines an electric heat pump with a combustion furnace. The heat pump can provide heating and cooling, while the furnace supplies another heating source.

Can I keep my existing furnace?

Often, yes, provided the furnace is suitable and compatible with the new heat pump, indoor coil and control system. The contractor should verify the complete combination rather than assuming compatibility.

Does a dual-fuel heat pump use gas all winter?

Not necessarily. The purpose of the system is to allow the heat pump and furnace to operate under different conditions. The heat pump may handle a substantial portion of the heating season.

Does a dual-fuel system save electricity?

The system may reduce electrical heating demand by switching to combustion heat under selected conditions, but whether that lowers total household energy cost depends on electricity prices, fuel prices, equipment efficiency and operating strategy.

Does a dual-fuel heat pump need natural gas?

A conventional dual-fuel system requires a combustion heating source. Depending on the furnace, that can be natural gas or another approved fuel such as propane.

Can a heat pump and furnace run simultaneously?

That depends on the equipment and control strategy. Some systems primarily alternate between heat sources, while other configurations can use supplemental heating under defined circumstances.

What temperature should the furnace take over?

There is no universal temperature. It should be established based on heat-pump performance, furnace efficiency, building load, energy prices and the control strategy.

Is dual fuel suitable for cold climates?

It can be. A cold-climate heat pump can continue providing substantial heat at low outdoor temperatures while the furnace provides another heating option. Bosch, for example, publishes 100% heating capacity at 5°F for the IDS Ultra in its specified configuration.

Is a cold-climate heat pump the same as a dual-fuel heat pump?

No. Cold-climate describes the heat pump’s low-temperature capability. Dual fuel describes the combination of an electric heat pump with a combustion heating source.

What is AHRI certification?

AHRI certification provides rated performance information for HVAC equipment and matched system combinations. It is especially useful because the outdoor heat pump’s maximum published rating may not apply to every indoor coil and furnace combination.

Should I buy variable-speed equipment?

Variable-speed equipment can provide greater modulation and may improve part-load comfort and efficiency. The additional cost should be evaluated against the home’s load, climate, utility rates and expected operating hours.

Can I use a propane furnace?

Some furnaces can be configured for propane with an approved conversion kit. Bosch, for example, states that its applicable gas furnaces can be converted from natural gas to liquid propane using the manufacturer’s conversion provisions and qualified service personnel.

Final Buying Checklist

Final Takeaway

The best dual-fuel heat pump is not necessarily the one with the highest SEER2 number.

A dual-fuel system is a complete combination of a heat pump, furnace, indoor coil, blower, thermostat and control strategy.

The seven systems examined here cover several different approaches.

The Carrier Infinity 23 27VNA3 emphasizes premium variable-speed operation. The Carrier Performance 27TPA8 provides a two-stage alternative, while the Carrier Comfort 27SCA5 represents a simpler single-stage approach.

The Lennox SL25XPV and American Standard AccuComfort Platinum 20 provide premium variable-capacity/variable-speed approaches, while the Trane 20 TruComfort focuses on variable-speed operation with substantial published cold-weather performance.

The Bosch IDS Ultra is particularly interesting for cold-climate applications because Bosch publishes 100% heating capacity at 5°F at a COP of 2.1 for its specified configuration.

For packaged applications, systems such as the Trane EarthWise Hybrid Dual Fuel and Rheem Endeavor RDFXYC provide another architecture in which the heat pump and gas furnace are integrated into one outdoor cabinet.

Ultimately, the correct choice depends on the home’s heating load, climate, existing furnace, ductwork, electrical service, fuel availability, local energy prices and contractor expertise.

Before signing a contract, ask for the exact model numbers, Manual J calculation, AHRI-rated combination, low-temperature heating capacity and planned changeover strategy.

Those details tell you much more about the quality of a proposed dual-fuel installation than a single headline efficiency number.

Related Guide: Best Heat Pumps In The USA