Best Thermostat for a Heat Pump With Auxiliary and Emergency Heat

The Short Answer

On a heat pump with electric backup strips, the feature that matters most is an outdoor-temperature lockout for auxiliary heat: a setting that stops the strips from running when it is mild enough outside for the heat pump to cope on its own. Google’s own help page puts auxiliary heat at about 2 to 5 times the cost of running the heat pump.

How these were chosen: we compared published manufacturer specifications and the Bonneville Power Administration’s thermostat support sheets, which list the exact lockout settings on each model. We do not run our own heat pump trials.

What Kind of Thermostat Does a Heat Pump Need?

Any thermostat sold as heat-pump compatible can switch the compressor on and off. What separates them is how many stages and backup-heat wires they can drive. Look at the labels on your current thermostat’s terminals (not the wire colors):

• O or B: the reversing valve that flips the heat pump between heating and cooling. Google notes that a white wire or no wire in the O/B terminal usually means a conventional system, not a heat pump.
• AUX (often W1 or W2) and AUX2: auxiliary heat, usually electric strips, that helps when the heat pump falls behind.
• E: emergency heat, which runs the backup heat on its own when you switch the heat pump off. Our emergency heat vs auxiliary heat guide explains the difference.
• Y2: a second compressor stage on 2-stage heat pumps.
• Dual fuel: a heat pump paired with a gas or oil furnace instead of electric strips.

If you have an E wire, a 2-stage compressor or dual fuel, the ecobee Premium or the Nest Learning Thermostat covers it. For a simple single-stage heat pump with strips, a budget model works, but check how it handles the backup heat (below).

Why Auxiliary Heat Lockout Is the Feature to Buy For

A heat pump moves heat rather than making it. The backup (“auxiliary”) heat on most ducted systems is electric resistance strips, which make heat directly and cost far more per hour. The thermostat decides when to call for them.

Without a lockout, many thermostats bring on the strips whenever the house falls a couple of degrees behind the setpoint — after a setback, say, or when you nudge the temperature up — even on a day when the heat pump alone would have caught up. A lockout adds a simple rule: above a chosen outdoor temperature, the strips stay off.

Two related settings are worth knowing:

• Aux heat lockout (ecobee: “Aux Heat Max Outdoor Temperature”). Above this outdoor temperature, auxiliary heat will not run.
• Compressor lockout (ecobee: “Compressor Min Outdoor Temperature”). Below this outdoor temperature, the heat pump itself is switched off. Set too high, it forces the house onto strip heat. Cold-climate heat pumps can usually run much lower than older units — check your heat pump’s documentation.

If you are not sure what your thermostat is doing today, read emergency heat vs auxiliary heat first, then why aux heat won’t turn off.

1. ecobee Smart Thermostat Premium: Best Overall

ecobee exposes both lockouts directly in Settings → Installation Settings → Thresholds, which is why it is the easiest recommendation for a ducted heat pump. BPA’s support sheets list the same two settings across the ecobee3 lite, 4, 5, Enhanced and Premium.

• Compatibility (ecobee spec): heat pumps up to 2 heat / 2 cool plus 2 stages of aux heat; conventional 2H/2C; boilers.
• In the box: one SmartSensor for a second room, and a Power Extender Kit for homes without a C wire.
• Worth knowing: it is the most expensive pick here. The cheaper ecobee Essential is newer than BPA’s June 2023 sheet, so confirm its threshold settings before buying it for a heat pump.

We may earn a commission if you buy through these links, at no extra cost to you. Products are chosen on published specifications; we do not test them in-house (how we choose).

2. Google Nest Learning Thermostat (4th gen): Best Hands-Off Option

Nest handles aux heat with Heat Pump Balance. Max Comfort (the default) uses aux heat readily; Balanced and Max Savings push the lockout temperature progressively lower; turning it Off lets you set the lockout temperature yourself in the equipment settings.

• Compatibility (Google spec): heat pumps up to 3 stages with 1 or 2 stages of auxiliary and emergency heat (O/B, AUX, AUX2, E).
• Power: Google says it works without a C wire in most homes, and that in limited cases (under 1%) a C wire or Nest Power Connector is needed.
• Worth knowing: the default is Max Comfort. If you buy a Nest for a heat pump, change that setting on day one. The Amazon listing below bundles a Nest Temperature Sensor.

We may earn a commission if you buy through these links, at no extra cost to you. Products are chosen on published specifications; we do not test them in-house (how we choose).

3. Honeywell T10 Pro or Lyric T6 Pro: If a Contractor Is Installing

Honeywell’s professional models document both lockouts. BPA lists the T10 Pro’s under “Equipment Lockouts” (installer setting 3120) and the Lyric T6 Pro’s as “Aux Heat Lock Out” (ISU 356) and “Balance Point” (ISU 355), using either a wired outdoor sensor or Wi-Fi weather data.

These are usually sold and set up through HVAC contractors, so we do not link a retail listing. If your installer offers one, ask them to set the lockouts before they leave.

4. Cielo Breez Max: For Ductless Mini-Splits

A ductless mini-split has no 24 V thermostat wiring and usually no strip heat, so none of the above applies. Cielo Breez Max sits on the wall or on its table stand and controls the indoor unit with infrared, like the handheld remote does. Cielo says its auto remote detection works with any mini-split brand; it runs from the included 5 V USB adapter, so there is no wiring, and it works with Alexa, Google Assistant and SmartThings.

We may earn a commission if you buy through these links, at no extra cost to you. Products are chosen on published specifications; we do not test them in-house (how we choose).

Budget Thermostats: Check Before You Buy

Cheaper smart thermostats — the Amazon Smart Thermostat, Honeywell Home T5, T9 and X2S, Wyze — can drive a heat pump, but none of them appears in BPA’s list of models with documented lockout settings. That does not prove a model lacks one; it means you should find the setting in its manual before you buy it for a heat pump with electric backup.

Of these, the Honeywell X2S is the one we would start with on a simple heat pump: Honeywell lists heat pumps up to 2 heat/1 cool with electric backup, it works with Alexa, Google and Apple Home through Matter, and it needs a C wire. The Nest Thermostat (2020) handles auxiliary or emergency heat on one wire, without an E terminal.

We may earn a commission if you buy through these links, at no extra cost to you. Products are chosen on published specifications; we do not test them in-house (how we choose).

On a gas furnace or a heat pump without strips, this matters much less, and a budget model is a reasonable choice: see the best smart thermostats under $100.

Before You Install: Five Things to Confirm

1. Your system type: heat pump with electric strips, dual fuel (heat pump plus gas furnace), or ductless.
2. Your wiring: photograph the old thermostat’s terminals. Heat pumps use an O or B reversing-valve wire; aux heat is usually W1/AUX; emergency heat is E.
3. Whether you have a C wire. The ecobee includes a Power Extender Kit; Nest rarely needs one.
4. Your heat pump’s documented low-temperature limit, before you set the compressor lockout.
5. Your utility’s thermostat rebate. Many utilities run their own programmes, so check your utility’s website rather than assuming one applies.

Frequently Asked Questions

What kind of thermostat do I need for a heat pump?

One that is heat-pump compatible and has a terminal for every wire you have: O/B for the reversing valve, AUX or W for auxiliary heat, and E if you have a separate emergency heat wire. For 2-stage or dual-fuel systems, choose a model that lists them, such as the ecobee Premium or the Nest Learning Thermostat (4th gen).

Which thermostats work with a heat pump with emergency heat?

The Nest Learning Thermostat (4th gen) lists 1 or 2 stages of auxiliary and emergency heat with a separate E terminal. The ecobee Premium supports 2 stages of auxiliary heat. The Nest Thermostat (2020) handles auxiliary or emergency heat on the AUX wire but has no E terminal.

Can a smart thermostat control a dual-fuel heat pump?

Yes. ecobee lists dual-fuel systems as compatible, and Google lists dual fuel as supported for Nest Learning Thermostats. Google strongly recommends professional installation for dual fuel on the Nest Thermostat (2020).

What is aux heat lockout?

A setting that stops auxiliary (backup) heat from running when the outdoor temperature is above a threshold you choose, so the cheaper heat pump carries the load on mild days.

Do all smart thermostats work with heat pumps?

Most can switch a heat pump on and off, but not all document an outdoor-temperature lockout for auxiliary heat. That setting is what separates a good heat pump thermostat from an adequate one.

Can I use a Nest thermostat with a heat pump?

Yes. The Nest Learning Thermostat (4th gen) supports heat pumps with up to 3 stages and 1 or 2 stages of auxiliary and emergency heat. Change Heat Pump Balance from its Max Comfort default if you want aux heat used less.

Is ecobee or Nest better for a heat pump?

ecobee gives you direct numeric control of both the aux heat and compressor lockouts. Nest automates the choice through Heat Pump Balance, with a manual lockout available if you turn that off. Choose ecobee for control, Nest for simplicity.

What thermostat should I use for a mini-split?

A mini-split usually has no 24 V thermostat wiring. Use an infrared controller such as the Cielo Breez Max, which replaces the handheld remote.

Related Guides

• Smart thermostat Black Friday prices — ecobee and Nest prices to beat this month
• Heat pump vs furnace (2026) — which costs less to run where you live
• Best smart thermostat (2026) — all our picks by wiring and budget
• Emergency heat vs auxiliary heat — what each mode does and which one you choose
• Aux heat won’t turn off? — start with the outdoor unit
• Heat pump blowing cold air? — defrost, settings and when to call a pro
• Nest aux heat running too much — the Heat Pump Balance fix in detail
• ecobee Premium vs Enhanced vs Essential — which ecobee to buy

Sources

• Bonneville Power Administration: PTCS Thermostat Support Sheets (June 2023)
• Google Nest Help: Heat Pump Balance
• Google Store: Nest Learning Thermostat (4th gen) specs and wiring compatibility
• ecobee: Smart Thermostat Premium specifications
• Mysa: Mini-Splits overview
• Cielo: Breez Max
• Google Nest Help: Nest thermostat technical specifications
• ecobee Support: What HVAC systems are ecobee thermostats compatible with?
• Honeywell Home: X2S Smart Thermostat