Before looking at features, confirm that the thermostat you're considering works with your boiler. The vast majority of modern smart thermostats use a simple on/off relay connection (2 wires) that is compatible with most standard gas combi boilers and heat-only (conventional) boilers. However, there are exceptions:

• OpenTherm-compatible boilers: Some thermostats (Netatmo, Tado, certain Honeywell models) support OpenTherm, a protocol that allows the thermostat to modulate the boiler's output rather than simply switching it on/off. This can improve efficiency by 10–15% on compatible boilers.
• Electric heating systems: Not all smart thermostats support electric storage heaters or direct electric radiators. Look specifically for models designed for electric systems.
• Underfloor heating: Requires a thermostat that supports the lower water temperature and slower response time of UFH systems. Heatmiser and Honeywell offer dedicated UFH-compatible models.
• Older millivolt systems: Some older gas fires and boilers use a millivolt signal rather than 240V switching. Most smart thermostats are incompatible — check before purchasing.

Most manufacturers provide online compatibility checkers on their websites. Use them before buying.

Geofencing is the single most impactful smart thermostat feature for most households. It uses your phone's GPS to know when you leave and return home, automatically switching between comfort and away temperatures. In a typical household, this eliminates the most common source of heating waste: the house being heated to 20°C while everyone is at work.

• Tado: Geofencing is included but the automation (switching modes without manual confirmation) requires the Auto-Assist subscription (approximately £3/month).
• Netatmo: Basic geofencing through the app is free. Works via HomeKit (Apple) or third-party automation tools.
• Hive: Geofencing included at no extra cost with the Hive app.
• Google Nest: Geofencing plus occupancy sensing via the built-in presence detector — no subscription required.

Some thermostats (most notably Google Nest) claim to "learn" your schedule and preferences. The learning works by observing when you manually adjust the temperature and inferring a schedule from your behaviour. In practice, results are mixed:

• Learning works well for households with very regular routines.
• Households with irregular schedules (shift workers, families with varying school runs) often find learning thermostats frustrating — the device cannot predict unpredictable behaviour.
• For most people, a manually programmed schedule on a standard programmable thermostat produces equal or better results than a learning algorithm.

Learning is a nice-to-have, not a must-have. Don't pay a significant premium for it alone.

A single smart thermostat controls the temperature of the room where it is located and uses that as the reference for the whole house. If you want room-by-room control, you need smart TRVs (thermostatic radiator valves). Key points:

• Tado Smart Radiator Thermostat: works with the Tado central thermostat. You can assign each room a different schedule and temperature target. Cost: approximately £60–£80 per valve.
• Netatmo Valves: similar concept, compatible with the Netatmo Smart Thermostat. No subscription.
• Standalone TRVs: brands like Danfoss Eco and Drayton Wiser offer smart TRVs that work without a central thermostat, useful for targeted room control.

For most homes with 1–2 occupants and predictable routines, a single smart thermostat is sufficient. Multi-zone becomes valuable in larger homes where rooms are used very differently.

The upfront price is only part of the picture. Consider the full 5-year cost:

• Tado: ~£130 upfront + £36/year Auto-Assist = ~£310 over 5 years.
• Netatmo: ~£140 upfront, no subscription = £140 over 5 years. Best value if you don't need automated geofencing.
• Hive: ~£130 upfront, no subscription for core features = ~£130 + optional professional installation (~£100). Strong ecosystem if you already use British Gas.
• Google Nest Learning: ~£220 upfront, no subscription = £220. Premium device, best integration with Google Home.

Compare our detailed smart thermostat comparison for full feature and price breakdowns.

Most smart thermostats are explicitly designed for DIY installation and include step-by-step guides in the app. The process typically takes 30–60 minutes and involves:

• Switching off the boiler and isolating the thermostat circuit.
• Photographing the existing wiring before disconnecting.
• Connecting 2–3 wires to the new base plate (usually a simple terminal block).
• Following the in-app pairing and configuration wizard.

If you are not comfortable with basic electrical work, or if your existing thermostat has more than 3 wires (indicating a more complex system), use a qualified heating engineer. In the UK, this should be Gas Safe registered for any work involving the gas circuit.