Smart thermostat installation: UK costs and what to check

Smart thermostat installation means swapping your old dial or programmer for a thermostat you control from your phone, then wiring it to your boiler so it can switch the heating and, on many systems, the hot water. Hive, Google Nest, tado and Drayton Wiser are the names most people ask about. All of them do the same core job. The real differences are in the app, the extras and whether you pay a subscription.

Fitting is usually a short job. A straight swap on existing wiring often takes two hours or less. It gets longer, and dearer, when there’s no thermostat wire, when the thermostat has to move to a better spot, or when a system with a hot water cylinder needs its wiring centre reworked.

What a smart thermostat install involves

Most smart thermostats come in two parts:

A receiver or relay that sits next to the boiler or wiring centre and switches the heating on and off. This part takes the mains wiring.
The thermostat that sits in a living space, measures the temperature and talks to the receiver, usually by radio.

Many also have a small hub that plugs into your router. If your wifi doesn’t reach the hall or the boiler cupboard, mention it when you ask for quotes, as the fitter may need to place the hub differently.

How the visit works

Check compatibility. The fitter looks at your boiler, your existing controls and how the system is wired. A combi with a single heating zone is the simplest case.
Isolate the power to the boiler and controls.
Remove the old controls and fit the receiver where the old programmer or wiring connection was.
Mount the thermostat in a room you use a lot, away from radiators, sunny windows and draughts.
Pair and test. The fitter links the devices, runs the heating and hot water, and checks the boiler responds.
Set up the app with you, including a schedule and, if you want it, geofencing that turns the heating down when everyone is out.

Ask the fitter to set a sensible schedule before they leave. A smart thermostat left on its default settings often runs the heating no less than your old one did.

Choosing a thermostat: the decisions that matter

Subscription and app

Owners often raise the worry that features move behind a paywall, or that the company stops supporting the app. Before you buy, check which features are free, what the thermostat does if the internet drops, and whether you can still change the temperature on the device itself.

OpenTherm and modulation

A basic smart thermostat just turns the boiler on and off. Some can talk to the boiler over OpenTherm or a maker’s own protocol and ask for lower flow temperatures instead. A condensing boiler runs more efficiently at lower temperatures, so this can matter more than any app feature. Ask whether your boiler supports it.

Hot water control

If you have a cylinder, you need a model that controls hot water as well as heating. With a combi, the boiler heats water on demand and you only need heating control.

Smart radiator valves

Smart TRVs let you heat rooms on their own schedule. They suit homes where some rooms sit empty for long spells. They also add batteries to change and a cost per radiator, so many people start with the main thermostat and add valves later.

Smart controls with a heat pump

A heat pump works best running steadily at low temperatures, guided by the outside temperature. Big setbacks and lots of shut valves can work against it. If you have a heat pump or are getting one, use the controls the installer designed with the system, and read our air source heat pump guide before adding extra devices. The heat pump installation page explains how the design is done.

Rules that apply

Boiler Plus (England). Since April 2018, every new gas or oil boiler in England must come with a timer and a room thermostat. A new gas combi also needs one extra measure from this list: flue gas heat recovery, weather compensation, load compensation, or smart controls with automation and optimisation. That’s why many installers include a smart thermostat in a new boiler quote. Our new boiler cost guide shows how this should appear on the quote.

Who can fit it. Wiring a thermostat into an existing circuit is electrical work, and most heating engineers do it routinely. If the fitter has to open the boiler casing on a gas boiler, they should be Gas Safe registered. Check their ID card, and the categories on the back, before work starts.

Landlords. If you let a property, choose controls your tenants can use without your account. A thermostat that only works through the landlord’s app causes problems at changeover.

How to compare quotes

Ask each fitter to confirm in writing:

whether the price includes the thermostat, or fitting only
the exact model, and whether it controls hot water
whether new wiring, a wireless receiver or wiring centre work is included
whether they will set up the app and a schedule with you
what warranty covers their work, separate from the maker’s warranty on the device

A quote for a full new wiring job is not like for like with a straight swap. If one price is much higher, ask what extra work it covers.

When it makes sense

A smart thermostat is a good upgrade if your current controls are a basic dial, a programmer you never change, or a thermostat in a cold hallway. It’s also the cheapest way to meet Boiler Plus when you replace a combi, so it’s worth pricing at the same time. If you’re booking your yearly boiler service, ask the engineer whether a lower flow temperature would help too. Read how in our boiler service guide.

Tell us your postcode and the system you have, and we’ll pass your request to heating engineers who cover your area.

Typical smart thermostat installation prices

Job	Typical UK price	Notes
Smart thermostat, supplied and fitted	£150 to £400	Straight swap on existing wiring. London and the South East sit at the top.
Fitting only (you buy the thermostat)	£60 to £150	Check the model suits your boiler before the visit.
Thermostat on its own (Hive, Nest, tado, Wiser)	£100 to £250	Device price only, no fitting.
New thermostat wiring or wireless receiver	£150 to £300 extra	When there is no thermostat now, or it has to move.
Full install with new wiring and commissioning	£350 to £600 or more	Older systems, or ones with no existing controls.
S-plan or Y-plan wiring centre rework	£200 to £400 extra	Systems with a hot water cylinder and motorised valves.
Smart radiator valve (TRV), per radiator	£55 to £110	Supply and fit. Some valve bodies need an adaptor or a drain down.

Sources: Fantastic Services 2026 thermostat price guide, BestBuilders (updated 19 August 2026) and Trade2Base (14 June 2026). Figures are indicative; get written quotes.

Smart thermostat installation by city

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Scotland

Wales

Northern Ireland

Belfast

Common questions

How much does it cost to have a smart thermostat installed?

Expect about £150 to £400 for a supplied and fitted smart thermostat on existing wiring, or £60 to £150 for fitting only if you buy the device. New wiring, a wireless receiver or a wiring centre rework adds £150 to £400.

Can I fit a smart thermostat myself?

Some battery and plug-in models are designed for DIY, but most need mains wiring at the boiler or wiring centre. If the job means opening the boiler casing, use a Gas Safe registered engineer. If you're not sure how your system is wired, pay for a fitter.

Will a smart thermostat work with my boiler?

Most do. Combi, system and regular boilers can all take one, but the wiring differs. Many modern boilers also support OpenTherm, which lets the thermostat turn the flame down instead of just switching it on and off. Check the maker's compatibility tool before you buy.

Do I need a smart thermostat with a new boiler?

In England, every new gas or oil boiler needs a timer and room thermostat. A new gas combi also needs one extra energy-saving measure, and smart controls with automation and optimisation are one of the four options.

Do smart thermostats save money?

They can, but the savings in adverts are not guaranteed. The Energy Saving Trust (May 2026) says installing a programmer, room thermostat and thermostatic radiator valves can save about £110 a year, and turning the thermostat down from 22°C to 21°C about £90 a year in Great Britain. Those figures are for a full set of controls used well, not for a smart thermostat alone. If you already have a programmer and TRVs, a smart model may add little.

Are smart radiator valves worth it?

They help when rooms are used at different times, such as a spare bedroom or home office. They cost about £55 to £110 per radiator fitted, and they need batteries. With a heat pump, closing lots of rooms can harm efficiency, so ask your installer first.