Most smart thermostat guides online are written for American homes, where one thermostat runs a furnace and an air conditioner. UK heating works differently: a boiler or heat pump feeding radiators or underfloor heating, with either a combi or a separate hot water cylinder. That changes which controls are worth buying.
I’ve fitted and set up most of the systems below on customers’ boilers and heat pumps. This guide covers what a smart thermostat changes, the one technical detail that matters most when choosing, how the main UK options compare, and when it’s worth getting a professional to fit it.
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Quick answer
- Gas boiler, simple needs: Hive, or Drayton Wiser if you want to avoid any subscription.
- Most efficient boiler control: an OpenTherm thermostat such as tado X, Drayton Wiser or Netatmo Smart Modulating, provided your boiler supports it.
- Different temperatures in different rooms: Drayton Wiser, tado X or Honeywell evohome, with smart radiator valves.
- Heat pump: start with the manufacturer’s own controller; only add a third-party thermostat if it works with your heat pump’s weather compensation.
What a Smart Thermostat Changes
A standard room thermostat does one job: it switches your boiler on when the room drops below the set temperature and off when it gets there. A programmer or timer decides when that’s allowed to happen. A smart thermostat combines both and adds a phone app, so you can change schedules and temperatures from anywhere.
The better ones go further:
- Optimisation: learning how long your home takes to warm up, so it reaches temperature at the time you set rather than only starting then.
- Geofencing: turning the heating down when everyone’s phone has left the house, and back up as you head home.
- Weather awareness: using the local forecast to adjust when the heating comes on.
- Hot water scheduling: on systems with a cylinder, controlling when the hot water heats.
- Zoning: with smart radiator valves, setting different rooms to different temperatures.
What a smart thermostat can’t do is fix a system that’s badly balanced, has undersized radiators or loses heat through an uninsulated loft. Controls make a good system cheaper to run; they don’t rescue a poor one.
On/Off or OpenTherm: The Detail That Matters Most
This is the part most buying guides skip. There are two ways a thermostat can talk to your boiler:
- On/off control: the thermostat simply switches the boiler on or off. The boiler runs at whatever flow temperature it’s set to until the room is warm, then stops.
- OpenTherm: the thermostat tells the boiler how much heat is needed, and the boiler turns its burner down to match. The radiators run cooler for longer, instead of hot and then off.
That matters because a condensing boiler is only at its most efficient when the water coming back from the radiators is cool enough for it to condense, roughly below 55°C. Lower, steadier flow temperatures keep it in that zone more of the time.
Two things to check before paying extra for OpenTherm:
- Your boiler supports it. Many modern boilers do, but not all, and some need an add-on module. Check the boiler manual or ask your installer.
- Worcester Bosch is the exception. Its boilers use their own control system (EMS), so an OpenTherm thermostat needs a separate converter. On those boilers, Worcester’s own EasyControl is the simpler route.
If your boiler doesn’t support OpenTherm, an on/off smart thermostat is still a big step up from a dial and a mechanical timer. You just won’t get the modulation benefit.
UK Smart Thermostats Compared
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| Thermostat | Typical price | Boiler control | Room by room | Subscription | Best for |
|---|---|---|---|---|---|
| Hive Thermostat Check on Amazon | £120 to £170 with hub | On/off; OpenTherm on newer models with OpenTherm combi boilers | Yes, with Hive radiator valves | Optional (Hive+) | Simple, well-supported app |
| tado X Check on Amazon | £135 to £160 starter kit | OpenTherm or on/off | Yes, with tado X radiator valves | Some automatic features need Auto-Assist | The most features, including geofencing |
| Drayton Wiser Check on Amazon | From around £110 | OpenTherm (on OpenTherm hubs) or on/off | Yes, strong radiator valve range | None | Best value for multi-room control |
| Honeywell evohome Check on Amazon | Around £230 for the controller | Mainly on/off; check your model | Yes, up to 12 zones | None | Larger homes needing serious zoning |
| Netatmo Smart Modulating Thermostat Check on Amazon | Around £200 | OpenTherm | No | None | OpenTherm control with no subscription |
| Google Nest (Learning 3rd gen, Thermostat E) Check on Amazon | £199 to £219 | OpenTherm or on/off | No | None | Existing Nest users (see note below) |
A note on Nest: Google has said it won’t launch new Nest thermostats in Europe, and the newer fourth-generation model isn’t sold in the UK. The 3rd generation Learning Thermostat and Thermostat E are still on sale while stocks last and work well, but I’d weigh up long-term support before buying one new.
To check which of these work properly with your particular boiler or heat pump, see our smart heating controls compatibility guide.
If You Have a Heat Pump
Heat pumps change the picture. A heat pump is most efficient running low and steady, guided by weather compensation: it adjusts the flow temperature to the outside temperature, rather than producing a burst of heat and switching off. Most third-party smart thermostats work as simple on/off controls on a heat pump, which can undo that.
My advice to customers:
- Start with the manufacturer’s own controls and app, for example Vaillant’s sensoCOMFORT and myVAILLANT, Daikin’s Onecta, or Mitsubishi’s MELCloud for Ecodan. They work with the heat pump’s weather compensation rather than against it.
- If you want a third-party system, check it supports your heat pump properly. tado’s Heat Pump Optimizer X (about £220) connects directly to supported Panasonic Aquarea, Vaillant, Daikin, Fujitsu, Atlantic and Saunier Duval models.
- Avoid big night-time setbacks. Dropping the temperature by more than a degree or two makes the heat pump work hard to recover in the morning, when it’s least efficient.
The bigger saving for most heat pump owners comes from the right heat pump electricity tariff, not the thermostat on the wall.
Upgrading From a Dial Thermostat
If you’ve still got a dial on the wall and a separate timer near the boiler, a smart thermostat is one of the cheapest worthwhile upgrades you can make. Most kits include a receiver that’s wired in at the boiler, replacing or working alongside the old timer, and a thermostat that sits on the wall or on a stand.
On wiring: UK systems don’t use the “C-wire” you’ll read about in American guides. The receiver is usually wired to the boiler at mains voltage (230V), or to the boiler’s low-voltage OpenTherm terminals. Swapping a battery wall thermostat is simple, but anything that involves wiring at the boiler should be done by a qualified heating engineer or electrician. A wrong connection can stop the boiler working or create an electrical hazard.
Two rules worth knowing:
- Boiler Plus (England): since April 2018, every new gas boiler must be fitted with a timer and a room thermostat. A new combi also needs one extra energy-saving measure, and smart controls with automation and optimisation count as one of the options.
- Renting: get your landlord’s permission before changing the heating controls.
Keep your radiator valves. A smart thermostat controls the room it’s in; thermostatic radiator valves still stop other rooms overheating. Just leave the radiator in the thermostat’s room without one. If you want different temperatures in different rooms, our guide to smart heating zones explains the options.
What It Costs and How to Look After It
- Thermostat kits: roughly £110 to £230, depending on the brand and whether a hub is included.
- Smart radiator valves: around £40 to £80 each, so kitting out a whole house adds up quickly. Many people start with the main rooms.
- Professional fitting: worth paying for if wiring at the boiler is involved. Ask for a fixed price up front.
- Subscriptions: Hive offers an optional paid plan, and tado charges for some of its automatic features. Drayton Wiser, Honeywell evohome, Netatmo and Nest don’t charge a subscription.
Once it’s in, a little upkeep keeps it working properly:
- Replace the batteries in wireless thermostats and radiator valves once a year, before winter.
- Keep the app and the device firmware updated.
- Use holiday or away mode rather than switching the system off completely in cold weather, so pipes are protected from freezing.
- At the start of each heating season, check every room heats when it should.
Which One Should You Choose?
1. Do you have a heat pump?
Yes: use the manufacturer’s controls first. Add tado’s Heat Pump Optimizer X only if your model is supported.
2. Does your boiler support OpenTherm?
Yes: tado X, Drayton Wiser, Netatmo Smart Modulating or a newer Hive model get the most from it. Worcester Bosch owners: look at EasyControl.
3. Do you want different temperatures in different rooms?
Yes: Drayton Wiser, tado X or Honeywell evohome, with smart radiator valves.
4. Just want simple app control?
Hive, or Drayton Wiser if you’d rather avoid any subscription.
FAQs
Can I fit a smart thermostat myself?
If it’s a straight swap for a battery wall thermostat, often yes. If it means wiring a receiver in at the boiler, use a qualified heating engineer or electrician.
Do smart thermostats save money?
They can, mainly by not heating an empty home and by starting the heating at the right time. How much depends on how you used your old controls; if you already ran a tight schedule, expect less.
Do I need a subscription?
Not with most brands. Hive’s core features are free, with an optional paid plan. tado charges for some automatic features and has changed its pricing before, so check its current terms. Drayton Wiser, Honeywell evohome, Netatmo and Nest don’t charge a subscription.
Will a smart thermostat work with my heat pump?
Most will switch a heat pump on and off, but that can work against its weather compensation. Start with the manufacturer’s own controls, and only add a third-party system that properly supports your model.
Is a Nest still worth buying in the UK?
It still works well, but Google has said it won’t launch new Nest thermostats in Europe. If long-term support matters to you, tado, Drayton Wiser or Hive are safer choices.
Do I still need radiator valves?
Yes. They stop the rooms away from the thermostat overheating. Leave the radiator in the thermostat’s room without one.