Smart Thermostats 
A heat pump needs a thermostat that understands staging and backup heat, or you can end up paying far more to run it than necessary. The wrong thermostat, or the right thermostat set up the wrong way, can quietly trigger expensive electric resistance backup heat on a system that’s supposed to be efficient.
Buying for a heat pump means paying attention to a few things a standard furnace thermostat doesn’t need.
Why Heat Pumps Need a Different Kind of Thermostat
A gas furnace is essentially binary: it’s either firing or it isn’t, and it recovers from a temperature setback quickly and cheaply. A heat pump is different. It moves heat from outside air rather than generating it, which makes it efficient most of the time, but its capacity drops as outdoor temperature drops. Below a certain outdoor temperature (the system’s “balance point”), the heat pump alone can’t keep up with heat loss, and the system brings on auxiliary heat (usually electric resistance strips, sometimes a gas furnace in a dual-fuel setup) to make up the difference.
Auxiliary heat (sometimes labeled “aux heat” or “emergency heat”) is far more expensive to run than the heat pump’s normal compressor-driven heating. A thermostat that doesn’t manage staging correctly can bring on aux heat far more often than the system needs it, quietly inflating your electricity bill without anything looking obviously wrong.
This is the core reason a heat pump needs a thermostat built with heat pumps in mind, not a generic thermostat that happens to have a wire terminal for one.
What to Look For Specifically
Heat pump balance point awareness. A good heat pump thermostat lets you configure (or automatically learns) the outdoor temperature at which aux heat is needed, rather than triggering it any time the house is more than a degree or two below setpoint.
Multi-stage support. Two-stage or variable-capacity heat pumps need a thermostat that can independently manage stage 1 (compressor only) and stage 2 (compressor plus aux) rather than jumping straight to aux heat.
Aux-heat lockout settings. Look for a thermostat that lets you set a temperature above which aux heat is locked out entirely. This is useful for preventing it from firing unnecessarily on mild days when the heat pump alone should be able to keep up.
Compressor protection / minimum cycle timers. Less heat-pump-specific, but worth having: short-cycling a compressor repeatedly shortens its life. Most decent thermostats handle this automatically.
Dual-fuel support, if you have a heat pump paired with a gas furnace as backup instead of electric resistance strips. The thermostat needs to know the crossover point between the two systems, and manage it based on relative running cost, not just temperature difference.
The One Heat-Pump Mistake to Avoid
Don’t set large temperature setbacks on a heat pump system. This is the single most common and costly mistake.
Drop the temperature significantly overnight or while away (the kind of deep setback that saves real money on a gas furnace), and the heat pump has to make up a larger temperature gap when it’s time to recover. Heat pump capacity is limited, especially in cold weather, so a large gap often can’t be closed by the compressor alone within a reasonable time, and the system falls back on aux heat to catch up quickly. You end up burning expensive backup heat because you tried to save money with a big setback.
The safer approach: use smaller setbacks (a couple of degrees, not five or six) on a heat pump system, especially in cold weather, and let the thermostat’s own adaptive recovery feature (like ecobee’s eco+) manage the ramp-up gradually rather than trying to force a big jump quickly.
Exact numbers vary by climate, house insulation, and heat pump capacity, so treat this as a general principle rather than a fixed rule, but the direction of the mistake is consistent across systems.
For more on setting up schedules that don’t backfire this way, see Smart Thermostat Schedule Tips to Maximize Savings.
Best-Suited Models
ecobee has the most explicit, well-documented heat pump and aux-heat support among mainstream smart thermostats. It’s built with configurable balance points and aux-heat management specifically for heat pump and dual-fuel setups, which is why it tends to be the default recommendation for heat pump homes on this site.
Other central HVAC thermostats (Nest Learning Thermostat, Honeywell T9) support heat pump wiring (the O/B terminal for the reversing valve) but generally offer less granular control over aux-heat behaviour than ecobee does.
See ecobee Smart Thermostat Review for the full breakdown of its heat pump-specific features.
How This Differs From a Standard Gas Furnace Setup
| Gas furnace | Heat pump | |
|---|---|---|
| Setback strategy | Large setbacks (4-6°C) save money with fast, cheap recovery | Small setbacks (2-3°C) recommended; large ones risk triggering aux heat |
| Backup heat | None (furnace is the only heat source) | Aux/emergency heat exists as a backup; managing when it engages matters a lot |
| Wiring | R, C, W, Y, G | Adds O/B for reversing valve; possibly W2/aux terminals |
| Multi-stage | Some furnaces are two-stage | Common (compressor stage plus aux stage) |
| Thermostat priority | Reliable scheduling | Reliable scheduling and aux-heat/staging management |
If you’re moving from a gas furnace to a heat pump (or your home already has one and you’re upgrading the thermostat), adjust the schedule habits that worked well on a furnace. See Best Smart Thermostats for Heat Pumps & Mini-Splits for model-specific picks.
Heat pump-relevant picks: aux-heat management, staging support, O/B wiring, dual-fuel support
Frequently Asked Questions
Do I need a special thermostat for a heat pump?
You don’t need a completely different category of device, but you do want one with genuine heat pump support: configurable aux-heat behaviour, multi-stage management, and O/B wiring for the reversing valve. A thermostat without these can trigger backup heat more than necessary.
What is aux heat on a heat pump thermostat?
Auxiliary (or emergency) heat is a backup heat source (usually electric resistance strips, sometimes a gas furnace in dual-fuel systems) that engages when the heat pump alone can’t keep up with heat loss, typically in very cold weather. It’s significantly more expensive to run than the heat pump’s normal operation.
Why does my heat pump thermostat keep switching to aux heat?
Common causes are large temperature setbacks that create a bigger gap than the compressor can close quickly, very cold outdoor temperatures near or below your system’s balance point, or an aux-heat lockout setting that isn’t configured. Reducing setback depth is often the simplest fix.
Should I use big temperature setbacks with a heat pump like I would with a furnace?
No, this is the most common heat-pump thermostat mistake. Large setbacks that work well on a gas furnace can force a heat pump into expensive aux heat during recovery. Use smaller setbacks and let adaptive recovery features manage the ramp-up gradually.
Which smart thermostat is best for a heat pump?
ecobee has the most explicit and well-documented aux-heat and staging support among mainstream smart thermostats, which is why it’s generally the top recommendation for heat pump homes. Nest Learning Thermostat and Honeywell T9 also support heat pump wiring but with less granular aux-heat control.
What’s the difference between a heat pump thermostat setup and a gas furnace setup?
The wiring adds an O/B terminal for the reversing valve, and possibly separate aux-heat terminals. The thermostat also needs to manage when backup heat engages, a concept a gas furnace setup doesn’t have at all.
