A radiator thermostat (thermostatic radiator valve or TRV) is a self-regulating device that automatically controls room temperature by adjusting hot water flow into individual radiators. Smart Radiator Thermostats like tado° offer remote control, scheduling, and smart features that can reduce heating bills.
A radiator thermostat, also commonly known as a thermostatic radiator valve (TRV), controls the air temperature in a room by automatically adjusting the flow of hot water into the radiator.
Its purpose is to make it easier and more cost-effective to warm or cool your home.
Even if your home has a single central boiler system, this technology allows you to create different heating zones throughout your house. By installing a thermostatic radiator valve on individual radiators in a hot-water or steam heating system, you can control the temperature of each room separately to improve comfort and stop wasting energy.
A radiator thermostat is a self-regulating device. The way it works is simple and straightforward. Using a valve mechanism, it adjusts the flow of hot water into your radiator based on the surrounding room temperature.
It consists of two main parts:
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Inside the valve head is a capsule filled with either liquid or wax. When the room temperature changes. If the room gets colder, the capsule contracts. This pulls a pin inside the valve body, allowing more hot water to enter the radiator and raise the temperature. If the room gets warmer, the capsule expands. This pushes the pin down, restricting hot water flow and preventing overheating.
Thermostatic radiator valves use either liquid-filled or wax-filled capsules:
Liquid thermostatic radiator valves generally give you more consistent temperature control and maintain their performance characteristics over time, unlike wax-filled models which can become less responsive as the wax crystallizes with repeated heating cycles.
There are significant differences between manual and thermostatic radiator valves.
Radiators usually have two valves:
The lockshield valve typically has a plastic cap and is not designed for regular adjustment. The radiator control valves are either manual, or thermostatic.
Manual radiator valves require you to physically turn them to adjust heat levels.
They work similarly to a tap: turning the valve up allows more hot water into the radiator, and turning it down reduces the heat output. Once the room reaches the desired temperature, you must manually adjust the valve to avoid overheating and wasting energy.
Manual valves are simple to operate, generally smaller, and less automated. However, they only work if you remember to adjust them on or off. Forgetting can lead to unnecessary energy use and add to your energy bills.
Thermostatic radiator valves automatically regulate room temperature.
You set the desired temperature, and then it monitors the room temperature, shuts off hot water flow once the target is reached and reopens when the temperature drops. Unlike manual valves, TRVs operate independently helping to prevent overheating, reduce energy waste and lower your heating bills. Overall, thermostatic radiator valves offer greater efficiency and convenience, making them a modern solution for home heating.
Ideally, yes. For the best results, thermostatic radiator valves should be used alongside a room thermostat.
This is because the room thermostat measures the temperature in the room where it’s installed.
If the temperature drops below the set level, it signals the boiler to switch on. Thermostatic radiator valves then regulate individual rooms to prevent overheating.
Together, they balance heating across your home while helping you save money on energy.
It's worth distinguishing between two different scenarios:
This is by far the most common situation – for example when upgrading to a smart TRV or when the existing head has stopped responding. There is no need to drain the heating system. Simply unscrew the old valve head (release the union nut or clip), fit the new one, and you're done.
This is more involved and requires draining the system first. Most competent DIYers can manage it, but if you're unsure, it's worth calling a heating engineer.
If the valve plunger moves freely but temperature regulation fails, the thermostat capsule may no longer expand or contract correctly. In this case, replacement is necessary. If you use Smart TRVs, check the battery power and replace them if necessary, before replacing the unit.
This is the most common issue, especially if you haven’t used your radiator valves in a long time. To fix it:
If the plunger can’t be freed, the valve must be replaced. You can prevent the valve sticking with an annual inspection and lubrication with WD40.
Avoid installing a TRV in the same room as your main boiler thermostat.
If the TRV switches off before the boiler thermostat reaches its target temperature, it can interfere with overall heating control. Even though TRVs operate automatically, inspect them annually to ensure they function correctly.
A Smart Radiator Thermostat is the next generation of home heating control that allows you to control room temperatures remotely via your smartphone. Smart Radiator Thermostats:
They work similarly to traditional thermostatic radiator valves but with added intelligence and connectivity.
Standard thermostatic radiator valves allow basic manual control, usually using a 0–5 scale. With tado°, you can do more. You can set very precise temperatures and control multiple rooms all with one app. You can adjust your heating remotely when you're not home, and optimise your energy use automatically using features like geofencing. Smart radiator thermostats are convenient, energy-efficient and easy to use.
By installing tado° Smart Radiator Thermostats, you can optimise your heating, reduce energy waste and lower household bills while keeping your home comfortable. Transform your heating system from wasteful to intelligent. The tado° Smart Radiator Thermostat installs in minutes, works with your existing radiators, and starts saving energy from day one.
Using the tado° app, you can create temperature schedules, set heating zones, and cut unnecessary heating – all included free with your tado° device. The optional AI Assist subscription unlocks additional smart automations and takes intelligent heating to the next level.
AI Assist includes advanced features like Adaptive Heating, which learns the unique heat-up and cool-down characteristics of each room to fine-tune control, Geofencing that automatically stops heating when everyone is away, and Preheat Before Arrival that uses machine learning to predict when you'll return home. Customers using AI Assist features can achieve up to 55%** more cost savings compared to the average tado° user.
*Based on internal data averaged across all tado° customers, collected up to 30/11/2023.
**Based on internal modelling comparing the use of tado° AI Assist vs the free tado° app. Actual savings depend on household characteristics, usage patterns and external factors.
Most TRVs can be installed as a DIY project if you're comfortable with basic plumbing. However, you'll need to drain your heating system first. If unsure, professional installation ensures proper setup and system balance. The tado° App provides step-by-step installation guidance tailored to your specific heating system.
They are different terms describing the same thing. Thermostatic Radiator Valve (TRV) is the technical industry term used by heating engineers. Radiator thermostat is a more consumer-friendly name that emphasizes the temperature control function. Both refer to the complete device that automatically regulates room temperature by adjusting hot water flow into your radiator.
Almost. Install TRVs on all radiators except one in the same room as your main thermostat, or leave one radiator without a TRV to act as a bypass and prevent boiler cycling. This is considered best practice according to UK heating regulations.
Basic TRVs offer manual temperature control per room using a simple dial. Smart TRVs like tado° add app control, scheduling, geofencing, room-by-room optimization, and real-time energy tracking – typically saving an additional 10-20% on heating costs through intelligent automation and remote access.
