The best smart thermostats of 2026 for heat pumps and boilers

Almost certainly: most smart thermostats work with furnaces and hot-water boilers, usually as a simple on/off switch. Some, mainly European models, also support OpenTherm, which lets the thermostat turn a boiler's output down instead of just switching it on and off, helping a condensing boiler run more efficiently. Check your system on the thermostat maker's compatibility list. Electric baseboard heaters are different: they run on line voltage and need a smart thermostat designed for them.

No, with a gas furnace or boiler it's usually cheaper to heat your home only when you need it, using a schedule. Your home loses heat to the outside all the time, and the warmer it's kept, the faster it loses heat, so heating an empty house wastes energy. Heat pumps are the exception: they run most efficiently at a steady, moderate output, so avoid long switch-offs and keep setbacks to 1 or 2°C.

It depends on your habits: the savings come from heating fewer hours and to lower temperatures, not from the device itself. If the heat already goes down whenever you're out, gains will be modest; if it runs on a fixed schedule whether you're home or not, features like geofencing and room-by-room control make a real difference. To estimate, add up a year of heating use from your bills, in cubic metres or gigajoules for gas or kWh for electricity, and multiply it by your rate: every 5% you cut takes about 5% off that cost.

Not always: installing a thermostat isn't gas work, and most furnace and boiler thermostats use low-voltage wiring, so swapping one is a common DIY job. Turn off the power to the system first and label the wires before you disconnect the old unit. If the wiring means opening the furnace or boiler, or your heaters run on line voltage, hire a licensed electrician or a heating technician; many brands also offer installation. If you rent, ask your landlord before changing the heating controls.

Usually because the Wi-Fi signal where the thermostat or its hub sits is too weak, or because the router or its password has changed. Most thermostats only use the 2.4 GHz band, so a mesh system that merges bands can confuse the setup. Move the hub closer to the router or add an access point, then reconnect it in the app. Many models keep the last schedule or temperature running while offline, so the heating doesn't simply stop.