For most heat pump owners, ecobee is the better choice. It gives you explicit, adjustable temperature thresholds for when backup heat can and cannot run. Nest works well, but its AUX heat handling is controlled through four presets rather than degree-level settings, which means less control when you need it most.
The one thing that separates them for heat pump owners
The core difference comes down to one question: can you set the exact outdoor temperature at which your backup heat is allowed to turn on?
With ecobee, yes. Two settings in the equipment menu control this precisely:
- Compressor Min Outdoor Temperature: the lowest outdoor temperature at which the heat pump compressor runs. Default is 35°F. You can lower this to 0°F or disable it entirely on cold-climate heat pumps. Below this threshold, the system switches to AUX only.
- Aux Heat Max Outdoor Temperature: the highest outdoor temperature at which AUX heat is allowed to run. Default is 70°F. This prevents AUX from firing on mild days when the heat pump is more than capable.
With Nest, the control is coarser. Heat Pump Balance offers four modes: Max Comfort (prioritizes AUX whenever recovery is slow), Balanced, Max Savings (minimizes AUX as much as possible), and Off. If you want to set a specific lockout temperature, you have to set Heat Pump Balance to Off first, then enter a manual threshold. Even then, the interface is less transparent about exactly when AUX will engage.
If you’re on a conventional gas furnace or a simple electric system, this distinction doesn’t matter. Both thermostats learn your schedule, control humidity, and connect to your phone equally well. For heat pump owners, the ecobee settings are concrete and auditable. The Nest presets require more trust in the algorithm.
Wiring and heat pump compatibility
Both thermostats support the standard heat pump terminal set: R, C, Y, G, O/B for reversing valve, W2/AUX for backup heat, and E for emergency heat. Both handle 2-stage compressors via Y1/Y2 and dual-fuel systems (gas backup paired with a heat pump).
C-wire situation differs between them. Nest ships with a Power Connector accessory that allows most installations without a C wire. Ecobee includes a Power Extender Kit (PEK) that achieves the same result using the G wire. If your system has a C wire already, both install without adapters.
One practical note: thermostat selection often comes up during heat pump installation itself. Some contractor quotes include thermostat replacement as part of the scope; others don’t. A missing thermostat line item can be a signal worth checking against the rest of the bid — is the electrical assessment and permit itemized too, or is this a bid that’s cutting scope broadly?
AUX heat control: the real comparison
This is where the gap between the two becomes concrete.
Ecobee settings (SmartThermostat Premium and Enhanced):
| Setting | Default | Range |
|---|---|---|
| Compressor Min Outdoor Temp | 35°F | 0°F to 65°F, or disabled |
| Aux Heat Max Outdoor Temp | 70°F | Adjustable or disabled |
These live in the equipment configuration menu (installer or advanced settings). You can tune the Compressor Min down to 0°F if you have a cold-climate unit rated for sub-zero operation, or disable it entirely on a system like a Mitsubishi Hyper-Heat rated to -13°F.
Nest Heat Pump Balance modes:
- Max Comfort: runs AUX aggressively to hit setpoint fast
- Balanced: uses AUX when recovery takes more than a few minutes
- Max Savings: delays AUX as long as possible
- Off: disables automatic balance logic; you set a manual AUX lockout temp
On most heat pumps, Balanced or Max Savings works fine without any adjustment. But if you want to audit exactly when your backup heat is running, ecobee gives you the data. Its app shows AUX heat runtime separately in the home report. Nest’s energy history groups runtime differently.
For a third option worth mentioning: the Honeywell Home T10 Pro (wired, not wireless) supports an AUX heat balance point via ISU 3120 in the installer menu. It also accepts a wired outdoor temperature sensor, which makes the lockout more accurate than any Wi-Fi-based outdoor temperature fetch. If your installer is already configuring the system, a wired sensor setup through the T10 Pro is the most reliable way to enforce a hard cutoff.
Room sensors
Ecobee SmartThermostat Premium ships with one SmartSensor. It averages the temperature across the main unit and any sensors to determine when to call for heat or cooling. Additional sensors run about $79 for a 2-pack.
Nest requires purchasing Temperature Sensors separately at $39 each. The scheduling logic is different: you assign sensors to specific 2-hour blocks, rather than having all sensors active simultaneously. In a large home where one or two rooms are chronically cold, ecobee’s always-on averaging approach tends to catch the problem faster.
The Mitsubishi variable-speed caveat
Here’s what matters for thermostat selection on a Mitsubishi MXZ-3C30NAHZ2, or any Mitsubishi variable-speed unit: both Nest and ecobee can control a Mitsubishi via standard 24V thermostat wire. They’ll turn the system on and off and stage it. What they cannot do is communicate with the inverter directly. To access Mitsubishi’s full variable-speed modulation (the feature that makes SEER 20 possible in real conditions), you need either Kumo Cloud (Mitsubishi’s Wi-Fi module) or the PAR-40MAA wall controller.
In practice, running a Mitsubishi Hyper-Heat through ecobee or Nest means you’re using it as a staged system. It still works well and is still more efficient than single-stage equipment. But if full inverter communication is the reason you’re buying a premium variable-speed system, confirm the controls setup with your contractor before the install.
Nest vs ecobee: side-by-side
| Feature | Nest Learning (4th gen) | ecobee SmartThermostat Premium |
|---|---|---|
| Price (MSRP) | ~$279-299 | ~$219-249 |
| AUX lockout control | 4 presets + manual when off | Exact °F settings |
| C-wire required | No (Power Connector included) | No (PEK included) |
| Room sensors included | None (buy separately, $39/ea) | 1 SmartSensor included |
| Heat pump balance point | Mode-based | Degree-level |
| Mitsubishi/inverter compatibility | Standard staging only | Standard staging only |
| Display | Color, round | Color, rectangular touchscreen |
| Apple HomeKit | Via Google Home bridge | Native |
Which one to buy
Buy ecobee if you have a heat pump and want control over when AUX heat runs. The Compressor Min and Aux Max settings are the main reason. You’ll also get a room sensor in the box and cleaner runtime reporting for heat pump systems.
Buy Nest if you’re on a gas furnace, electric resistance, or a heat pump where you’d rather set it and forget it. The Heat Pump Balance presets work fine for most installations, and the thermostat itself is thinner and easier to use without configuration.
If you’re replacing a thermostat as part of a new heat pump installation, check whether it’s actually in the contractor’s scope, then ask what they recommend for the specific equipment. Contractors installing Mitsubishi often have a preference based on how they commission the controls. The thermostat model matters less than making sure the wiring, staging, and AUX lockout are configured correctly after install.
Wiring note: Both Nest and ecobee operate on 24V AC control voltage. If you’re swapping out your own thermostat, label every wire before removing the old unit. The O/B wire controls the reversing valve on a heat pump and must be configured correctly in the new thermostat’s setup. An incorrect O/B setting will cause your system to heat when it should cool, or vice versa. If you’re unsure whether your system uses O (energized in cooling) or B (energized in heating), check the existing thermostat’s wiring or your equipment documentation before proceeding. When in doubt, have a licensed HVAC technician handle the swap.
Whichever thermostat you land on, the real payoff comes from the setpoints you actually run. Use the Thermostat Savings Calculator to see what a heat-pump-friendly schedule is worth in your climate.
