First, check your wiring — it decides everything
Before any of this matters, find out what your system actually is. Google’s own troubleshooting list is the clearest published guide to reading your own wall plate, and it works whichever thermostat you end up buying:
No O/B wire means you do not have a heat pump. O/B is the reversing-valve wire — the one that tells the outdoor unit to run backwards for heat. If it is absent, you have a conventional system and this page is the wrong one; start from our main smart thermostat ranking instead.
No W2 or AUX wire means you have no auxiliary heat. A heat pump with no backup strips cannot run expensive emergency heat, which makes the whole aux-lockout question moot — buy on the normal criteria. This is more common on mini-splits and on newer cold-climate installs.
Wires in both W1 and W2 indicate dual fuel — a heat pump with a gas or oil furnace as the backup rather than resistance strips. Read the dual fuel section below before you buy, because the headline feature on our top pick explicitly does not apply to you.
And the perennial one: the C wire. Both Nest models in our registry are recorded as commonly needing a C wire or Google’s power connector; the ecobee Premium ships a Power Extender Kit in the box, which is a genuine advantage in an older house. Our what is a C wire guide explains how to tell what you have before you order anything.
What Heat Pump Balance actually does
This is the feature the page turns on, so here is exactly what Google publishes about it rather than a paraphrase.
Heat Pump Balance governs how often auxiliary heat runs. Google directs you to the Google Home app to find it “if you have a Nest Learning Thermostat (4th gen) or a Nest Thermostat” — which is why both of our Nest picks qualify and why the gap between them is not this feature. There are four settings: Max Comfort, the default, which reaches your target temperature even if that means expensive AUX heat, so AUX turns on sooner and more often; Balanced, with a lockout temperature between the extremes; Max Savings, with a lower lockout temperature so AUX turns on later and less often; and Off, where the thermostat uses AUX based on a lockout temperature you set by hand.
The part worth paying for is what happens when it is on: Google states that “the thermostat sets the lockout temperature automatically based on how the heat pump is performing”, and that it uses Wi-Fi weather data to decide when to switch to AUX. You are not choosing 32°F or 25°F from a dropdown and hoping. You are choosing how much discomfort you will tolerate, and the thermostat works out the temperature.
Three published limits, all of which we would rather you heard from us than discovered in January. It needs Wi-Fi. Google is explicit that the thermostat must be connected, and that without Wi-Fi it suggests Early-On but “the thermostat won’t take specific steps to avoid expensive AUX heating”. It does not work with dual fuel systems — on those you set the lockout temperature by hand in the Equipment menu. And AUX use ultimately depends on your system: Google says some systems will need AUX to keep heating even on Max Savings, so this is a thermostat feature, not a physics exemption.
Why the Learning model is the pick over the cheap one
Both Nest models get Heat Pump Balance, so the step up has to be justified on something else. For a heat pump it is: Google publishes three advanced settings — Aux upstage timer, Droop and Minimum delay — that exist only on the 4th-gen Nest Learning Thermostat, and only when Heat Pump Balance is switched off. That is the difference between having a dial and having the controls behind the dial. If your heat pump is oversized, undersized, or in a climate where the strips keep engaging on mild mornings, those are the knobs an installer would reach for.
The 4th gen also ships a remote temperature sensor in the box, which matters more on a heat pump than on a furnace: heat pumps deliver lower-temperature air over longer runtimes, so a house heats unevenly in a way a single wall sensor reports badly. Our registry records it as Wi-Fi, Matter and Thread, with Google Home and Alexa support — although Google’s own help page on Alexa control is worth reading first, because it documents real limitations on Eco, Off and Emergency Heat commands through the Alexa skill. The honest cons: it is the priciest thermostat we list, it may still need a C wire, and it is genuinely overkill on a simple single-zone system with no aux heat at all.
The plain Nest Thermostat is the value answer and not a consolation prize. Same named feature, same automatic lockout, far less money, Matter support, auto-scheduling. What you give up is the advanced aux timers, the included sensor and the hardware. If your heat pump behaves itself and you mainly want to stop the strips running on a 45°F morning, this is the one to buy. Cons: no sensor in the box, fewer features generally, and the same C-wire caveat.
The ecobee pick, and the gap we will not paper over
Here is the honest position. We read ecobee’s own Smart Thermostat Premium product page on the date in the sources below, and heat pumps, auxiliary heat and dual fuel are not mentioned on it at all. What ecobee does publish there: ENERGY STAR certification across the line, a SmartSensor included in the box on Premium, Siri or Alexa built in, “works in harmony with leading smart home ecosystems including Apple Home”, and savings of “up to 26%*” on annual heating and cooling costs where the asterisk resolves to “compared to a hold of 72°F/22°C” and the footnote to an internal April 2021 analysis. We are reporting that claim as ecobee frames it, not endorsing the number.
So we cannot tell you what the ecobee does automatically with your aux heat, because its own marketing page does not say, and we are not going to fill the gap from memory or from a forum. What we can tell you is why it is still on this page: it is the only pick here that works with Apple Home as well as Alexa and Google, and it includes a Power Extender Kit for homes with no C wire — which, in the kind of older house that is having a heat pump retrofitted, is often the difference between a 20-minute install and calling someone. If you are in Apple’s ecosystem, or you know you have no C wire, buy it and then read your installation manual’s threshold settings carefully.
Cons: priciest of the mainstream three, a larger footprint on the wall, some extras are model-dependent across the Premium / Enhanced / Essential line (ecobee notes the Enhanced “only supports accessories connected to the thermostat by one wire”), and the aux-heat behavior is undocumented on the product page.
Not picked, and why
The Amazon Smart Thermostat is the obvious absence, since it is the cheapest thermostat we list and it appears on our thermostats for Alexa page. Three reasons it is not here. It requires a C wire with no adapter in the box, which rules out exactly the retrofit houses this page is written for. It is Alexa-only, and Amazon’s own help page states the unit has no speaker or microphone, so voice control runs through a separate Alexa device or the app. And we found no published Amazon statement about auxiliary heat lockout on a heat pump — so rather than guess, we left it off a page whose entire criterion is that behavior. It may well handle a heat pump perfectly; we cannot cite it.
The three picks, scored on heat pump behavior
'Not published' means we read the maker's own page on the date in the sources below and found no statement — it is not a claim the feature is absent. Nest rows come from Google's Heat Pump Balance support article; ecobee rows from ecobee's Smart Thermostat Premium product page. Savings depend on your equipment, your climate and your habits; nothing here is an HVAC recommendation for your specific system. | Nest Learning (4th gen) | Nest Thermostat | ecobee Premium |
|---|
| Automatic aux heat lockout | Yes — Heat Pump Balance | Yes — Heat Pump Balance | Not published on the product page |
|---|
| Lockout temperature set by | The thermostat, from heat pump performance + weather | The thermostat, from heat pump performance + weather | Not published |
|---|
| Advanced aux settings (upstage timer, droop, minimum delay) | Yes — this model only, with Balance off | No | Not published |
|---|
| Works with dual fuel | Yes, but Balance does not — lockout set by hand in Equipment | Yes, but Balance does not — lockout set by hand | Not published |
|---|
| Needs Wi-Fi for the savings feature | Yes — Google states this explicitly | Yes — Google states this explicitly | Not applicable |
|---|
| Remote sensor in the box | Yes | No | Yes — SmartSensor on Premium |
|---|
| No-C-wire adapter included | No — may need a C wire or power connector | No — may need a C wire or power connector | Yes — Power Extender Kit |
|---|
| Ecosystems | Google Home, Alexa, Matter, Thread | Google Home, Alexa, Matter | Apple Home, Alexa, Google, SmartThings, Matter |
|---|
| Voice built into the thermostat | No | No | Yes — Siri or Alexa |
|---|
| ENERGY STAR certified | Not read for this page | Not read for this page | Yes — published across the line |
|---|
| Monthly fee | No | No | No |
|---|
The row that decides the page is the first one, and the row that decides your install is the C wire. Everything in between is taste.
If you have dual fuel, read this instead
Dual fuel — a heat pump with a gas or oil furnace as the backup — is the configuration where our headline feature stops applying, and it deserves its own paragraph rather than a footnote. Google’s published position is that Heat Pump Balance does not work with dual fuel systems, and that on those systems you set the lockout temperature manually in the Equipment menu. That is not a reason to avoid a Nest; it is a reason to know that you, or your installer, are choosing the changeover temperature rather than delegating it.
The judgement you are making is a price comparison between two fuels at a given outdoor temperature, and it moves with utility rates, which is precisely why we are not going to publish a number for your house. Google’s own advice for wiring problems is to contact a local professional, and for the changeover point on a dual fuel system that advice is worth taking: an installer can compute it from your actual equipment and your actual tariff. If wires sit in both W1 and W2 on your current plate, that is your system.
What to expect from the savings
Two framings, both federal, both honest about variability. ENERGY STAR certifies smart thermostats on demonstrated field performance in heating and cooling, and the U.S. Department of Energy’s write-up on connected thermostats treats them as a gateway to savings rather than a guaranteed percentage. We are not going to turn either into a dollar figure for your house: a heat pump’s running cost is dominated by your climate, your envelope and your electricity rate, and the thermostat’s contribution is mostly the aux-heat decision this page is built around.
What we will say is where the leverage is. If your strips are engaging on mild mornings because the thermostat is set to recover quickly, a setting change costs nothing and Google’s own 2-to-5x multiplier tells you the direction of the effect. If you are going from a manual thermostat to any scheduled one, our do smart thermostats save money guide works through what is actually attributable to the device, and our running cost guide covers the rest of the house. If you are still deciding between brands on general grounds rather than heat pump grounds, the Nest vs ecobee comparison is the head-to-head.
