Electric Heater Thermostat Types: A UK Guide to Choosing

Electric heater thermostats fall into a few clear groups. Mechanical (analogue) dials use a bimetallic strip or gas-filled bellows. Digital thermostats use an electronic sensor. Programmable thermostats add a timer, and smart thermostats add internet control. Storage heaters have their own control set of charge dials and a timer. The right one depends on how you use the room, how often it is occupied and how much fine control you want.

This guide explains how each type works, how to tell which one you already have, and how to match a thermostat to a heater before you buy.

TL;DR

• A thermostat switches the heater’s element on and off to hold a set temperature. Mechanical ones do it with a bending metal strip or a gas-filled bellows, digital ones with an electronic sensor.
• Manual thermostats need you to adjust them. Programmable ones add a timer. Smart ones add app, voice or remote control.
• Storage heaters work differently: they charge off-peak and combine charge control, a thermostat and a timer.
• Check the heater’s rating, the voltage and whether the thermostat is built in or separate before you replace or add one.
• For fixed wall-mounted or towel-rail heating, a timer or a heater with a built-in thermostat usually gives the best day-to-day control.

Table of Contents

• How a thermostat controls an electric heater
• The main electric heater thermostat types
• How to tell which thermostat you have
• Built-in thermostat or separate wall thermostat?
• Thermostats for bathrooms and towel rails
• Matching a thermostat to your heater
• Which type suits which room?
• Our perspective
• Shop electric heating and controls at Simco Direct
• FAQ
• Sources

How a thermostat controls an electric heater

An electric heater turns almost every watt it draws into heat. It has no way of knowing when a room is warm enough, so the thermostat does that job. It senses the air temperature and opens the circuit when the room reaches your setting, then closes it again when the room cools.

The simplest versions are mechanical. Mechanical thermostats rely on thermal expansion to open and close an electrical circuit, and the two most common designs use bimetallic strips and gas-filled bellows. In the bimetallic version, two different metals are bonded together. One expands more than the other as it warms, so the strip bends and breaks the circuit. As the room cools the strip straightens and the heating comes back on.

That is why a heater with a mechanical thermostat clicks on and off. The click is the contacts opening and closing. Between clicks the room temperature drifts a little above and below your setting, which is normal for this type.

Digital thermostats do the same job with an electronic temperature sensor and a small controller. They tend to hold the temperature in a tighter band and show the actual room temperature on a display. HomeServe describes traditional analogue thermostats as temperature dials and digital thermostats as having electronic sensors, with programmable versions running heating at set times and smart versions controlled from a smartphone.

The main electric heater thermostat types

Here is how the common types compare in everyday use.

Mechanical thermostats

These are the dial-and-click type. They are robust and cheap, and there is little to go wrong. The trade-off is that the numbers on the dial are rarely calibrated to actual degrees. You find your comfortable setting by trial and error, then leave it. They suit a spare room or workshop where you want warmth now and do not need a precise figure.

Digital thermostats

A digital unit lets you choose a target such as 20°C and reads the room temperature back to you. Many electric radiators and panel heaters use this. It is easier to repeat the same setting every day, and many also have a basic timer or an open-window detection mode. If you are heating a bedroom, home office or bathroom where you want a consistent result, digital is a sensible step up from a dial.

Programmable thermostats

A programmable thermostat is a thermostat and a timer in one box. The Energy Saving Trust defines a programmable room thermostat as a combined timer and thermostat: it lets you set both heating schedules and target temperatures, including different temperatures at different times of day. Its guidance is that matching target temperatures and heating periods to your routine improves comfort and avoids unnecessary energy use.

In practice that means the heater can be warm when you wake and when you get home, and off or on a lower setting while the room is empty.

Smart thermostats

A smart thermostat does what a conventional control does and adds internet connectivity. According to the Rural Design Centre’s guide to heating controls, smart controls let you manage, schedule and adjust heating remotely through an app, web browser or text message, and features can include learning, geolocation, optimisation, zoning and voice control. Some also connect with smart radiator valves.

The features to look for on electric heating are room-by-room zoning, a schedule you can override from your phone and clear reporting of what the heater is doing. If you want to see how app control works on a different kind of heater, this Bluetooth app-controlled thermostatic heater shows the same idea of setting a target temperature from your phone, though it is a diesel unit for vehicles and not a mains home heater.

Bluetooth control is a halfway house. It works within a few metres of the heater, which is fine for adjusting a heater in the room you are in. It will not let you turn the heat on from the train. For that you need Wi-Fi or a hub.

Storage heater controls

Storage heaters are a separate case because they heat bricks overnight and release warmth through the day. The Energy Saving Trust notes that modern units commonly combine automatic charge control, a thermostat and a programmer or timer, while older models commonly use input and output dials. Its guide to electric storage heater controls adds that modern controls may include app control and automatic charge control that reacts to indoor and outdoor temperatures and the previous day’s demand.

The same guide explains that storage heaters charge during cheaper off-peak periods such as Economy 7 or Economy 10 hours, with the meter or a timer switch deciding when the off-peak circuit is live. If you are replacing an older unit, a modern one such as the Dimplex XLE storage heater is the kind of product where automatic charge control is worth looking for.

How to tell which thermostat you have

You can usually work it out in a minute at the heater.

1. A dial with numbers or symbols and no screen. This is a mechanical thermostat. You may hear a click as it switches.
2. A display showing a temperature, with up and down buttons. This is a digital thermostat.
3. A display with day and time settings, or on and off period buttons. This is a programmable thermostat.
4. A Wi-Fi or Bluetooth symbol, or a branded app. This is a smart thermostat.
5. Two dials labelled for input (charge) and output (release). This is the older style of storage heater control.

The Rural Design Centre’s distinctions are a handy test: a manual thermostat needs you to adjust the temperature by hand, a programmable one has a built-in timer that schedules heating on and off, and a smart control is internet-enabled.

If the heater has no obvious controls, look for a separate wall-mounted unit nearby. Some fixed electric heating uses a remote thermostat that senses the room and signals the heater, and the heater itself carries only a power switch.

Built-in thermostat or separate wall thermostat?

Plug-in heaters nearly always have the thermostat built in. Fixed heating, such as wall-mounted panel heaters, electric radiators and underfloor systems, can have either.

• Built-in: simple, no extra wiring, sensor sits in the heater. The drawback is that the sensor reads the temperature around the heater, which can be warmer than the middle of the room.
• Separate wall thermostat: reads the room more representatively and can control several heaters from one point. It needs wiring by a qualified electrician.

A fixed electric radiator such as the Galapagos horizontal electric thermofluid radiator or the Galapagos vertical thermofluid electric radiator is a good example of a product where you check the control options on the product page before ordering. A Dimplex LST electronic panel heater is an electronic-control panel heater that falls into the digital group. If you are heating a room with a wet system and want an electric element in a radiator, the GT vertical thermostatic heating element is an example of an element with its own thermostat.

Thermostats for bathrooms and towel rails

Bathrooms are where timers matter most. A towel rail that runs all day wastes energy, yet one that only comes on when you need it leaves towels cold. Our electrician checklist for heated towel rail timers goes through what to check before fitting one, including how the timer and thermostat work together.

For public and commercial washrooms and for places with vulnerable users, surface temperature matters as well as air temperature. Our guide to low surface temperature radiators explains the 43°C limit and what to look for.

Matching a thermostat to your heater

Before you buy a replacement or an add-on thermostat, work through these checks.

1. Heater rating. Find the wattage on the heater’s rating plate. A thermostat must be rated for at least the current the heater draws. A 3kW heater on a 230V supply draws roughly 13 amps, so a control rated for a smaller load is not suitable.
2. Plug-in or fixed. Plug-in heaters usually cannot have their thermostat swapped. Fixed heaters can, but the work belongs to a qualified electrician.
3. Control type. Check whether the heater has a thermostat built in, a separate wall unit or a timer-only control. Do not stack two thermostats on one heater without advice, because they can fight each other.
4. Load type. Some heaters use a run-back timer with an adjustable thermostat. Products such as the Consort SLVT run-back timer and adjustable thermostat and the Consort SLVTB run-back timer and adjustable thermostat are made for specific installations, so read the product page for the model it is intended to control.
5. Smart features. If you want app control, check the app is supported on your phone and whether it needs a hub or works over Bluetooth.
6. Tariff. If you are on Economy 7 or a similar tariff, your heater needs controls that work with the off-peak circuit.

A word on meters: RTS meters have been phased out in stages since 30 June 2025 because the radio-signal technology is outdated, and affected meters need replacing. If your off-peak heating was switched by an RTS meter, ask your supplier what the replacement means for your storage heater timing.

A note on electric baseboard heaters

“Baseboard” is mostly a North American term for a low, long convector heater fitted along the bottom of a wall. In the UK, the closest equivalents are low wall-mounted convector or panel heaters and skirting-style units. These typically use a built-in thermostat, either a dial or an electronic control, sometimes with a wall-mounted controller for several units. Check the product listing for the control type.

Which type suits which room?

• Bedroom: a digital or programmable thermostat, so the room is warm at bedtime and off overnight or held low.
• Home office: programmable, matched to your working hours.
• Bathroom: a timer on a towel rail or a heater with a thermostat and timer built in.
• Spare room or garage: mechanical is fine for occasional use.
• Whole-flat electric heating: smart zoning if you want to heat only occupied rooms.
• Storage heater homes: automatic charge control, as it adjusts to conditions rather than relying on you to guess the weather.

Whatever you choose, insulation and sizing matter just as much as the control. Our article on timers and insulation versus panel or convector choice explains why, and our radiator BTU per square metre guide helps you avoid oversizing. For rooms that never warm up, choosing a radiator for cold rooms covers size, type and running costs.

Our perspective

Most heating complaints we hear are not about the heater. They are about the control. A heater with the wrong thermostat runs when nobody is in, or never reaches the temperature people expect.

Our view is simple: buy the thermostat type for how the room is used. A dial is plenty for a spare room. A digital or programmable control repays itself in a room you use every day. Smart control earns its place when your routine changes often or you manage more than one property.

For commercial buyers, such as landlords, facilities teams and contractors, we would add one point: standardise. Using the same control type across a building makes it easier for staff and tenants to use, and easier for your electrician to maintain. We stock heating from a range of trusted brands, so you can match the control to the job rather than the other way round.

Carl

Shop electric heating and controls at Simco Direct

If you are ready to choose, we stock electric heaters, electric radiators, towel rails, storage heaters and controls for homes and commercial premises, with bulk discounts for trade buyers, fast UK delivery and a 30-day returns policy. Browse the range on the Simco Direct homepage, or look at a heater with Bluetooth control such as the Dimplex 3kW over door heater with Bluetooth control.

Not sure which control fits? Check the product page for the control type, and contact our team if you are buying for a commercial building.

FAQ

What type of thermostat do I have?

Look at the control. A numbered dial and no screen means mechanical. A temperature display with buttons means digital. A display with day and time settings means programmable, and a Wi-Fi or Bluetooth symbol or app means smart. Storage heaters often have separate input and output dials.

What is a smart heating thermostat?

It is a thermostat with internet connectivity. It does everything a conventional control does and lets you adjust and schedule heating remotely by app, web browser or text message. Features can include learning your routine, geolocation, zoning and voice control.

Is a digital thermostat better than a mechanical one?

For a room you use daily, usually yes. A digital thermostat lets you set a specific temperature and read the room temperature back. A mechanical dial is simpler and fine for occasional use, but its numbers rarely match real degrees.

Can I fit a new thermostat to my electric heater myself?

Not on a fixed heater. Wiring a thermostat into fixed electric heating should be done by a qualified electrician, who will check the rating of the control against the heater’s load. Plug-in heaters generally have a built-in thermostat that cannot be replaced.

How does a thermostat control an electric heater?

It senses the room temperature and opens the heater’s circuit when your target is reached, then closes it when the room cools. Mechanical versions do this with a bending metal strip or a gas-filled bellows, digital versions with an electronic sensor.

Sources

• How do thermostats work? (Explain that Stuff)
• How does a thermostat work? (HomeServe)
• Heating controls (Energy Saving Trust)
• Heating controls: types and features (Rural Design Centre)
• Electric storage heaters (Energy Saving Trust)
• How to use electric storage heater controls (Energy Saving Trust)
• RTS meter switch off (Energy Saving Trust)

Recommended

• Timers and Insulation Beat Panel or Convector Choice for UK Homes
• Electrician checklist: heated towel rail timers for UK homes
• Infrared Heater vs Convection: Which Suits Your Room?
• Avoid 46% Oversizing: Calculate Radiator BTU per m² for UK Homes