Which smart thermostat works with Alexa, Google Home and Apple Home?

Start with your system, not the app

ENERGY STAR advises buyers to confirm that a thermostat is compatible with their heating and cooling system. Many US homes run 24 V low-voltage equipment, and some use line voltage (120 or 240 V) baseboard heat. A thermostat made for one will not work on the other. Before you compare ecosystems, find out:

1. Is it a forced-air furnace with air conditioning, a heat pump, baseboard heat, a boiler or a mini-split?
2. What wires are at the thermostat? Read the letters on the terminals, not the colors. See thermostat wire colors.
3. Is there a C-wire? If not, read smart thermostat without a C-wire.
4. Do you have a heat pump? Then see heat pump smart thermostats.

If the old thermostat is marked 120 V or 240 V, or has thick wires joined with wire nuts, stop and look for a line-voltage model. Turn off power at the breaker before touching any wiring, and hire a licensed electrician if you are unsure and follow local code.

How each ecosystem treats thermostats

This is a good sign for Matter thermostats. It does not promise every feature. Scheduling, away modes, humidity and remote sensors may remain in the maker’s own app. Look at what the product page says you can do from each ecosystem.

Matter or ecosystem-specific?

Matter thermostat. Use it across ecosystems, with multi-admin so Apple Home and Alexa can both control it. You may need a Matter controller, and for a Thread model, a Thread border router. See What is Matter?.

Ecosystem-specific thermostat. Fine if you are committed to one ecosystem and the maker documents the features you want. The risk is switching later. If you use more than one ecosystem at home, prefer Matter.

Features that matter more than the logo

• Wiring support. Compatibility with your HVAC type, stages and heat pump reversing valve.
• Power. A C-wire adapter included in the box, or a design that works without one.
• Remote sensors. Helpful in homes with uneven temperatures; see room sensors.
• Schedules and geofencing. ENERGY STAR notes common features such as learning preferences, setting schedules for sleeping and away, geofencing and remote control.
• Utility programs. ENERGY STAR certified thermostats are designed to be compatible with programs some utilities offer. Check utility rebates before you buy.
• Offline behavior. Does the thermostat keep its schedule if the Wi-Fi is down?

Savings: what to expect

ENERGY STAR says heating and cooling make up almost half of a typical household’s energy bill, more than $900 a year, and that certified smart thermostats are independently certified to deliver energy savings from field data. The savings depend on how you set schedules, not on the voice assistant you use. See thermostat settings to save money.

Renters and landlord rules

Thermostats are wired to the building’s system. Check your lease and ask your landlord before you swap one. See thermostat limits and landlords. Keep the old thermostat to reinstall at move-out.