Heating controls are one of the cheaper ways to cut energy bills. The Energy Saving Trust estimates that installing and using heating controls effectively could save around £100 a year in Great Britain.1 Room-by-room control adds most in larger homes, where it avoids heating rooms nobody is using.
For most three-bedroom homes with a single heating zone, budget £180–£350 installed for a quality smart thermostat. For larger homes that benefit from room-by-room control via smart thermostatic radiator valves (TRVs), a whole-house system runs £500–£1,200 supply and fit.
Types of Heating Control
Basic manual thermostats
A simple on/off thermostat maintains a set temperature but offers no scheduling. These are now rarely installed in new or refurbished homes. Supply-only cost: £15–£40.
Programmable (digital) thermostats
A programmable thermostat lets you set different temperatures for different time periods, most allow at least two periods per day (heat up / set back). Some offer separate weekend programming. They do not learn your behaviour or respond to weather. Supply: £30–£80; installed: £100–£160 including an electrician or heating engineer.
Smart thermostats
Smart thermostats connect to your Wi-Fi and are controlled via a smartphone app. They add features such as:
- Geofencing, the system detects when you are approaching home and turns the heating on automatically
- Weather compensation, modulates boiler output based on outside temperature (important for heat pump efficiency)1
- Learning algorithms, some models learn your preferences and adjust schedules without manual programming
- Remote access, adjust temperature from anywhere
- Energy reports, show usage patterns by day, week, or month
Common systems in the UK include Hive Active Heating (British Gas), Nest Learning Thermostat (Google), tado°, Honeywell Home T6R, and Drayton Wiser. Costs: £100–£250 supply; £180–£350 installed.
Multi-zone smart systems with smart TRVs
Smart TRVs replace the head of each radiator valve and allow independent control of individual rooms. They communicate wirelessly with a central hub. This avoids heating empty bedrooms and is the most effective approach for larger homes.
Note: smart TRVs should not be fitted to every radiator simultaneously without a bypass radiator or a combi boiler that modulates, closing all TRVs at once creates pressure build-up or boiler short-cycling. Approved Document L puts the same point in one line: a wet heating system should ensure a minimum flow of water to avoid short-cycling.2 A heating engineer should plan the installation.
Cost Comparison Table
| Control type | Supply only | Installed (single zone) | Installed (whole house, 8 TRVs) |
|---|---|---|---|
| Manual thermostat | £15–£40 | £70–£120 | N/A |
| Programmable digital thermostat | £30–£80 | £100–£160 | N/A |
| Smart thermostat (Wi-Fi, single zone) | £100–£250 | £180–£350 | N/A |
| Smart thermostat + 8 smart TRVs | £300–£600 | - | £500–£1,000 |
| Multiroom systems (Wiser, tado°, Nest) | £250–£500 | - | £600–£1,200 |
Labour is typically carried out by a Gas Safe registered heating engineer (£50–£80/hour) or a qualified electrician where no gas work is involved.
Which System Works With My Boiler?
Most smart thermostats are designed to work with standard on/off-controlled combi and system boilers. However, compatibility matters:
- OpenTherm-compatible thermostats (several of the main smart brands offer models; check the exact one) can modulate boiler output rather than just switching it on and off. This reduces boiler cycling and improves efficiency. Check that your boiler supports OpenTherm before buying: many do, but some manufacturers use their own communication bus and need an adaptor module or their own controls.
- Heat pumps benefit strongly from weather compensation and modulating control. Some heat pump manufacturers supply their own dedicated controls (Vaillant sensoComfort, Daikin Madoka). Third-party thermostats must be confirmed compatible before purchase.
- Older boilers without OpenTherm will work with any smart thermostat via a standard two-wire dry-contact connection, you just lose modulation capability.
One thing to know before you spend money on controls: a wet heating system that is newly installed, or fully replaced including the appliance, emitters and pipework, has to be sized so it works at a maximum flow temperature of 55 °C or lower.2 A system designed to run that cool spends most of its life modulating rather than firing flat out and switching off, and weather or load compensation is the control that keeps it there. If an installer designs a new or fully replaced system to 75/65, ask why: the rule allows a higher temperature only where 55 °C is not feasible, and then the lowest design temperature possible.2
Building Regulations and Compliance
Under Part L of the Building Regulations, replacing a boiler in England pulls the controls up to the current standard with it, and a basic fixed-temperature thermostat alone does not meet it. Approved Document L Volume 1, 2021 edition, which came into force on 15 June 2022, sets the minimum as:
- Separate time control for space heating and hot water, unless the existing system already runs both off a single time controller2
- Thermostatic room controls for each room, satisfied in practice by a thermostat in one room plus thermostatic radiator valves (TRVs) on every heat emitter outside that room; TRVs should not be used in the same room as the thermostat2
- Boiler interlock, the boiler must not fire when there is no demand for heat2
There is a fourth requirement that most control guides miss. Where a gas combination boiler is installed in an existing dwelling, at least one of flue gas heat recovery, weather compensation, load compensation, or a smart thermostat with automation and optimisation has to go in with it, and the wet heating system itself has to reach 92% efficiency as defined by ErP.2 That is the rule the trade still calls Boiler Plus. It now sits in Approved Document L Volume 1 at paragraph 6.2 and Table 6.2, not in the 2018 edition of L1B where older guides still point, and a smart thermostat is one of the four ways to satisfy it, which is why so many boiler quotes now bundle one in.
This compliance is confirmed in the Competent Person Scheme certificate issued by the Gas Safe engineer. Smart thermostat installations generally exceed these requirements. Upgrading controls alone, with no change to the boiler or gas pipework, is normally not notifiable: Schedule 4 of the Building Regulations exempts adding a control device to an existing heating system where testing and adjustment would not affect how much energy it uses.3
Installation: What to Expect
A smart thermostat installation by a heating engineer typically takes 1–2 hours:
- Remove old thermostat and programmer
- Check wiring compatibility (most smart thermostats come with wiring guides and adaptors for the common two-wire, three-wire, and four-wire UK configurations)
- Mount new thermostat base plate and connect wiring
- Connect to Wi-Fi during setup; pair the receiver at the boiler
- Test heating and hot water demand across schedules
- Brief homeowner on app use
If TRVs are also being replaced, add 10–15 minutes per radiator. The engineer should verify the bypass radiator is not fitted with a TRV.
Expected Savings and Payback
The Energy Saving Trust’s published figure is for heating controls as a category, not for smart ones in particular: installing controls where there were none saves around £100 a year in Great Britain and £110 in Northern Ireland, and turning the thermostat down one degree, from 22 °C to 21 °C, saves £120 in Great Britain and £80 in Northern Ireland.1 Nobody official publishes a figure for the extra a smart thermostat delivers over a competent programmable one, so treat any number a salesperson quotes for that gap as an estimate rather than a measurement. Savings are higher for:
- Properties where occupancy patterns are irregular (geofencing delivers more benefit)
- Properties currently without any thermostat
- Larger homes where room-by-room control avoids heating unused spaces
At £180–£350 installed against roughly £100 a year saved, simple payback is nearer two to three and a half years, and only that quick if you had no working controls to begin with. The Energy Saving Trust puts the cost of adding a programmer, thermostat and TRVs to a house with none at around £600, or around £370 for TRVs alone where a programmer and thermostat are already there.1
What to Look For When Choosing
| Feature | Why it matters |
|---|---|
| OpenTherm compatibility | Modulates boiler; reduces cycling |
| Geofencing | Avoids heating empty home; automates holiday mode |
| Multi-zone capability | Needed for room-by-room control |
| App reliability and longevity | Check whether the manufacturer has a track record of maintaining app support |
| Hot water control | Important if you have a system boiler with a cylinder |
| Frost protection | Minimum safeguard when away in winter |
| Works without internet | Some systems fail to local fallback; confirm behaviour if broadband drops |
Avoid thermostats from obscure brands with no UK service or app track record, a thermostat that loses app support in three years has a very poor effective lifespan relative to the heating system it controls.
DIY Installation
Swapping an existing thermostat for a smart one is within the capability of a confident DIYer, but not all of the wiring is low voltage: the thermostat head is usually battery or bus-powered, while the receiver or wiring centre at the boiler usually runs at mains voltage (230 V). However:
- If the thermostat receiver connects to the same circuit as the boiler, isolate the boiler before wiring
- If you are unsure of the existing wiring, have a qualified electrician or heating engineer identify and label it before you start
- Gas work must never be touched during the process
Most manufacturers provide installation guides for common UK wiring configurations and telephone or chat support.
The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.
References (3)
Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.
- 1technicalfairEnergy Saving Trust, guidance.RN-1B36CGEnergy Saving Trust's consumer advice on thermostats and heating controls: room thermostats, programmers, thermostatic radiator valves and zoning, with indicative savings. Useful as the plain-English explanation of what each control does; the compliance requirement for controls on a new or replacement system sits in Approved Document L, not here. The page blocks automated fetching, so it is described from its title and publisher.
- 2technicalvery strongMinistry of Housing, Communities and Local Government.RN-L0FCJXThe in-force U-value tables a DIY insulation or door note must quote, with the exact numbers. Table 4.2, limiting U-values for new fabric elements in existing dwellings, sets roof 0.15, wall 0.18, floor 0.18, swimming pool basin 0.25, window 1.4 or Window Energy Rating Band B minimum, rooflight 2.2, doors with more than 60 per cent of the internal face glazed 1.4 or Doorset Energy Rating Band C minimum, and other doors 1.4 or Doorset Energy Rating Band B minimum. Table 4.3, for existing elements, gives a roof threshold of 0.35 and an improved value of 0.16, which is the figure a loft insulation note needs: paragraph 4.12 says a retained element whose U-value is higher than the column (a) threshold, for example through a loft or garage conversion, should be upgraded to the column (b) value. Paragraph 4.13 allows a lesser upgrade only where the improved value is not technically or functionally feasible or would not achieve a simple payback of 15 years or less. Paragraph 4.8 requires a replacement element to be no worse than the one it replaces as well as meeting Table 4.2. Paragraph 4.10 gives the heritage exception: where character must be maintained, a centre pane U-value of no more than 1.2 or low-emissivity secondary glazing. Note 9 records that the timber window concession of 1.6 or Band C ended on 14 June 2023. The 2021 edition came into force on 15 June 2022; a 2026 edition exists at https://assets.publishing.service.gov.uk/media/69c122a6cfa346b9d4704a55/ADL1_2026.pdf.
- 3technicalvery strongThe National Archives (legislation.gov.uk), guidance.RN-CC1O5HSchedule 4 lists building work that needs no building notice; item (g) covers a self-contained fixed service that is not a combustion appliance other than a fixed flueless gas cooker, so a flueless hob is exempt but flued appliances are not.
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Heating controls, Energy Saving Trust, accessed 9 September 2026. energysavingtrust.org.uk
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Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments, Ministry of Housing, Communities and Local Government, accessed 9 September 2026. assets.publishing.service.gov.uk
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The Building Regulations 2010, Schedule 4: Descriptions of work where no building notice or full plans application is required, The National Archives, accessed 30 September 2026. legislation.gov.uk
