Smart TRVs: Radiator Thermostats with App and Zone Control

A smart TRV is a battery-powered, motorised thermostatic radiator valve head: the initials stand for smart thermostatic radiator valve¹. It replaces the twist-and-guess head on a radiator's thermostatic valve body with an electronic one that holds a target temperature, follows a schedule, and reports back to an app or a hub. Like a mechanical TRV it works by throttling the hot water flowing into that radiator, but it decides when to do so from a sensor and a programme rather than from a wax capsule alone². Most connect to a home network so the room can be adjusted from a phone, and several will monitor a single radiator's temperature and energy use as well as change its setting remotely³.

The practical effect is room-by-room zoning on a heating system that has only one zone. A typical UK house has one room thermostat governing the whole of the wet circuit; smart TRVs let a bedroom run a different schedule from a living room without any new pipework or wiring. Savings claims vary widely and mostly come from manufacturers: tado° puts smart TRVs at an additional 10 to 20 per cent on heating costs over basic control⁴, Fuse Energy cites estimates of up to 15 to 20 per cent against a system with no zonal control⁵, and Drayton claims as much as 30 per cent for a full upgrade from a basic non-programmable thermostat⁶. Independent figures are lower and narrower in scope: the Energy Saving Trust puts TRVs added to a system that already has a programmer and thermostat at £30 a year in Great Britain and £40 in Northern Ireland⁷.

On cost, Which? found smart radiator valves typically cost between £35 and £80 each, about five times a traditional TRV, as of September 2026⁸. That is per radiator, before any hub, so the arithmetic scales quickly in a house with ten radiators. And a smart TRV never removes the dependencies that matter most: the boiler or heat pump, the fuel supply, the manufacturer's hub and app, and in many cases a cloud account.

What a smart TRV controls, and what it does not

A smart TRV controls one radiator. It carries an electronic sensor that regulates the room temperature to a programmed schedule³, and it throttles hot water flow into that radiator once the target is reached, exactly as a mechanical TRV does¹². What it does not control is the heat source. The boiler or heat pump still needs a call for heat from a room thermostat, programmer or appliance control; a set of radiator heads closing in every room while the appliance fires is a recipe for short cycling rather than saving.

That division explains why smart TRVs are sold as an addition to a system rather than a replacement for it. Netatmo describes a connected system as switching off the heat in the main room as soon as the desired temperature is reached, leaving the TRVs to fine-tune settings elsewhere³. Bosch positions its smart radiator thermostats the same way, as individual room control working with the EasyControl thermostat¹³.

Regulation reinforces the pairing. Viessmann states that Building Regulations require every radiator on a wet central heating system to have a TRV, apart from those in the same area as a room thermostat¹⁴, and the Planning Portal states that any new radiator installed will require a thermostatic radiator valve to be installed¹⁵. Leaving one radiator without a head, in the room with the main thermostat, is also the conventional way of retaining a path for flow. tado° describes the same practice: fit TRVs on all radiators except one in the room with the main thermostat, or leave one radiator without a TRV to act as a bypass and prevent boiler cycling⁴.

For the household, the independence gain is real but bounded. Rooms that are not in use stop being heated to living-room temperature, which cuts fuel demand. The system still depends on the gas or electricity supply, on the appliance, and on the control manufacturer continuing to run its hub and app.

Zoning, schedules, remote access and learning

The feature set is broadly consistent across brands, with differences in how much runs locally. Smart TRVs remove the need to adjust anything by hand, because scheduling is done remotely and multiple devices give room-to-room control¹². They allow individual rooms or zones to be controlled through a smartphone app¹, and Drayton states its heads connect to a home Wi-Fi network so they can be operated by app or by a voice assistant such as Alexa or Google Assistant¹⁶.

Beyond schedules, three behaviours matter in practice:

• Learning and prediction. Some smart TRVs learn household habits and the home's thermal performance, and over time predict when to adjust settings¹.
• Weather response. Some adjust temperatures based on weather conditions¹.
• Open window detection. Drayton states the Wiser Radiator Thermostat (2nd Generation) can automatically reduce heating when a window is left open⁹.

Reporting is the other half of the value. Drayton states that Wiser smart TRVs provide usage data straight to the smartphone app¹⁷, which is what turns a schedule into something a household can check and correct. Commissioning is generally wireless pairing, then naming the device (for example "Living room") and setting up a schedule¹⁶.

The caution is dependence. Remote access, voice control and learning all route through a manufacturer's app and, usually, its servers. Local control at the dial remains, and Drayton states Wiser heads can be managed by app, voice, preset schedules or manual control¹⁶, but the automation layer is not owned by the household. That trade-off is covered further under heating controls and energy independence.

How much a smart TRV saves: the claims and the evidence

The honest answer is that the range is wide and the strongest numbers come from manufacturers. tado° states smart TRVs typically save an additional 10 to 20 per cent on heating costs through intelligent automation and remote access⁴. Fuse Energy puts proper use of ordinary TRVs at around 10 per cent, with estimates of up to 15 to 20 per cent overall against a system with no zonal control⁵. Drayton claims as much as 30 per cent on annual heating bills when upgrading from a basic Class I non-programmable thermostat with no multi-room control to a smart thermostat with smart TRVs⁶, and cites up to 19 per cent for adding radiator thermostats to an existing Wiser system, with the 30 per cent figure attributed to BEAMA and Salford University research from 2021⁹.

Independent figures sit lower. The Energy Saving Trust is quoted at savings of around £75 a year for a smart thermostat¹⁸, and separately puts TRVs added to a system that already has a programmer and thermostat at £30 a year in Great Britain and £40 in Northern Ireland⁷. That Northern Ireland difference reflects fuel costs and is worth noting for anyone budgeting there.

The gap is not dishonesty so much as different baselines. A 30 per cent figure compares a smart system against the worst common alternative, a single non-programmable thermostat in a house with no room control. A £30 figure compares TRVs against a home that already has a programmer and a room thermostat. A household that already zones by habit, turning off unused rooms, should expect the lower end. Whether the payback works at £35 to £80 a head⁸ depends entirely on which baseline the home starts from. Do smart heating controls actually save money? takes the question further.

Smart TRVs and heat pumps: where setback on every radiator goes wrong

This is the single most important limitation on the page. BEAMA's Salford Energy House testing of air source heat pumps with TRVs found that using smart TRVs on all radiators to provide a setback between heating periods significantly increased heat pump cycling¹¹. The same testing programme is cited by Drayton as delivering 6 to 8 per cent energy savings without impacting heat pump performance¹⁹, so TRVs themselves are not the problem: the problem is closing most of the emitter circuit at once while the pump is trying to run at low flow temperature.

The recommendation that follows is explicit.

Two pieces of hardware support that. BEAMA states that a volumiser and automatic bypass valve should be installed alongside an air source heat pump where TRVs are used¹¹. On the control side, ClimateXchange describes the Scottish retrofit pattern as constant running with minimal setback, for example to 18 degrees Celsius, particularly in solid wall homes with radiator upgrades²⁰. A deep overnight drop on every radiator is the opposite of that.

There is an equivalent rule for boilers. A smart TRV in the same room as the main thermostat makes the two controls compete: Which? states temperature-limiting valves should not be used in the room where the main boiler thermostat is⁸, and Hive warns that a thermostat in the same room as a TRV-controlled radiator may never reach its target, leaving the heating on²¹. Bosch takes the same line, recommending a smart TRV on every radiator for optimum comfort but not on radiators in the room with the EasyControl¹³. See also why TRVs are often left off heat pump installations.

Wiser, tado°, Aqara and Bosch: which ecosystem fits which home

The ecosystem decision is effectively made when the first head is bought. Which? notes that most smart radiator valves will not work with another manufacturer's smart thermostat and connecting device⁸, so mixing brands across one heating system is generally not an option.

Wiser (Drayton) is a Zigbee system built around a hub. The Wiser Radiator Thermostat (2nd Generation) is Zigbee certified and compatible with all Wiser hubs, including the 1st Generation HubR, the 2nd Generation HubR and the 2nd Generation Non-relay Hub⁹. Drayton states Wiser connects with Matter, Amazon Alexa and Google Assistant, and that 2nd Generation Wiser can be integrated with wider smart home ecosystems for automations spanning multiple brands²².

tado° runs on Thread and integrates through Matter²³. The tado° Smart Radiator Thermostat X fits directly onto existing thermostatic valves for room-by-room control, and the heads clip on and can work alongside a central thermostat or independently, battery-powered with no wiring⁴. tado° Room Link syncs the central Smart Thermostat with the radiator thermostats in each room so each room can request heat individually²⁴. tado° states every Smart Thermostat includes remote control, Smart Schedule, smart home and voice assistant integration and Room Link at no additional cost, and that it is compatible with air-to-water, water-to-water and geothermal heat pumps²⁵.

Aqara offers the Radiator Thermostat W600, model WT-A03D / WT-A03E, with an M30 x 1.5 mm threaded connection²⁶, the common European valve thread.

Bosch ties its smart radiator thermostats to the EasyControl thermostat, with the recommendation of a head on every radiator except those in the room with the EasyControl itself¹³.

Brand-level detail sits on the Wiser heating controls, tado° smart thermostats and TRVs, Aqara heating controls and Bosch smart home heating controls pages, and the protocol differences on Zigbee, Matter, KNX and Wi-Fi for heating controls.

Cost per radiator, and the whole-house number

Which? found smart radiator valves typically cost between £35 and £80 each as of September 2026, roughly five times a traditional TRV, with the Habi Smart Thermostatic Radiator Head listed at £31 at Screwfix and the tado° Smart Radiator Thermostat at £74.99 at the tado° shop⁸. Drayton lists the Wiser Radiator Thermostat (2nd Generation) from £59.99, with free delivery over £75 and estimated delivery of 3 to 5 working days²⁷. Drayton has separately promoted 25 per cent off its Smart Radiator Thermostats²⁸. A tado° smart radiator attachment has been quoted at £79.99 as an addition to a thermostat²⁹. All of these are retail prices read in 2026 and change with promotions.

The whole-house figure matters more than the per-head price. The Energy Saving Trust puts adding TRVs to all radiators, where a programmer and thermostat already exist, at around £370, and a full set of programmer, room thermostat and TRVs at around £600 where no controls exist³⁰. Those are conventional TRV figures; at £35 to £80 a head, a smart set in a ten-radiator house sits well above them before any hub is counted.

Costs across the wider control set are gathered on how much heating controls cost.

Installation: valve compatibility, adapters and fitting without draining

The head unscrews and the new one screws on. Drayton states Wiser Radiator Thermostats are supplied with two adaptors providing compatibility with around 90 per cent of UK valve bodies, and that the system should not need draining down where radiators have existing mechanical TRVs¹⁰. Elsewhere Drayton states compatibility with over 95 per cent of existing radiator valves⁹ and, in its radiator guide, 95 per cent, noting that less common valves such as Oventrop, Herz, TA, Giacomini, Markaryd, Ondal and Vaillant may require additional adaptors¹⁷. Those two compatibility figures, around 90 per cent and 95 per cent, come from the same maker and are not reconciled; treat the lower one as the safer assumption.

tado° states its Smart Radiator Thermostat is compatible with most thermostatic radiator valves with adapters included as standard³¹, and that its heads fit onto an existing valve body in minutes with no wiring and no access to the boiler needed²³. Salus supplies its RA-ADAPT adaptor with selected TRVs for quick, tool-free installation³². Warmup states the Konekt Wireless eTRV fits all common radiator valves and mounts without draining any water or intervening in the heating system³³.

The dividing line is whether the radiator already has a thermostatic valve body. Which? is clear: a smart radiator valve can be installed without a professional if the radiator already has a TRV, but replacing manual valves will likely need a plumber⁸. Changing a valve body means isolating or draining part of the system, which is a different job in cost and risk.

1. Identify the existing valve: thermostatic body with a removable head, or a plain manual wheelhead.
2. Check the head thread or the adapter list for the brand chosen, including the less common bodies noted above¹⁷.
3. Where a thermostatic body exists, remove the old head and fit the new one with the supplied adapter, no draining required¹⁰.
4. Where only a manual valve exists, the valve body is changed, which is plumbing work⁸.
5. Pair the head wirelessly to the hub, name the room and set a schedule¹⁶.

More general guidance sits on installing and replacing heating controls and thermostatic radiator valves.

Specifications that matter: batteries, radio, range and noise

Batteries dominate the ownership experience, because a flat cell in a bedroom head means that room stops being controlled. Drayton states more than two years of battery life for the Wiser Radiator Thermostat (2nd Generation) using the included alkaline batteries under its standard operating conditions, on 2 x 1.5 V IEC LR6 (AA) alkaline or rechargeable 1.2 V IEC HR6 NiMH cells⁹. SONOFF states up to six months under normal use for the TRV Gen2 on two 2,000 mAh AA alkaline cells³⁴, and typically six months or more for the TRVZB on three AA alkaline batteries, not included³⁵. The spread reflects motor duty, radio and firmware rather than any single specification.

Noise is not a trivial specification. A motorised head sits on a radiator in a bedroom and drives several times a day; Salus quotes less than 25 dBA operating noise for the TRV3RF³⁶ and Drayton describes quieter operation for its second generation head⁹. Control mode matters too: advanced PI control, as on the TRV3RF³⁶, modulates the valve position rather than snapping between open and shut, which is gentler on both comfort and the heat source.

Drayton states its UK technical team is available Monday to Friday, 8am to 6pm, online and by phone, and the Wiser Radiator Thermostat (2nd Generation) carries a customer rating of 4.30 from 314 verified reviews⁹. Support arrangements and product lifetimes are worth weighing alongside the hardware: see smart heating controls, security, data and product support.

Temperature settings, condensation and the summer months

Smart TRVs are frequently used to hold unoccupied rooms at a floor temperature rather than switching them off entirely, which is a damp question as much as a fuel one. Home Energy Scotland advises keeping a home heated to at least 15 degrees Celsius, particularly during colder months³⁷, while the National Energy Action leaflet on condensation and mould advises keeping temperatures in all rooms in use above 18 degrees Celsius to reduce condensation forming³⁸. The two figures answer different questions: a minimum for an unused room, and a target for an occupied one. Smart Energy GB separately suggests turning TRVs in non-living rooms such as bathrooms, bedrooms and hallways down to the midway point [10 is not the source here; see below].

Over the summer, the valve pin is the concern. Manufacturer guidance is to check the instructions for the specific model, because some models may require battery removal or a specific standby mode to keep them in good working order³⁹. Removing batteries from a head that expects to exercise its pin periodically is not always the right move, which is why the model-specific instruction matters.

Room-by-room targets are set out in more detail on what temperature each room should be and heating schedules, setback and leaving the heating on.

What a smart TRV does for energy independence

It shrinks demand without touching supply. A household with smart TRVs heats fewer rooms to full temperature for fewer hours, which reduces the gas or electricity drawn, and it gains visibility, since usage data arrives in the app per room¹⁷. In a home with one room thermostat, it is the cheapest route to zoning, because it needs no pipework, no zone valves and no wiring: heads clip onto existing valve bodies in minutes with no access to the boiler²³.

What it does not do is remove dependence. The heat source, its fuel and its supplier are unchanged. The hub and app belong to a manufacturer, and heads from one brand generally will not talk to another brand's thermostat⁸. Cloud services underpin remote access and learning. And the head itself depends on batteries that the household must replace, somewhere between six months and two years apart depending on the model³⁵. The gain is control and a modest reduction in consumption, not autonomy.