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Best smart thermostats 2021: Save on heating costs now

If you’re to buy one smart device, then make it a smart thermostat. Not only will it make your heating system easier to use, a smart thermostat can save money and provide a more comfortable home environment. We’ve tested every single major smart thermostat available. And, we do it all using a custom test rig in the same environment, so we can accurately compare and contrast.

We test each unit for ease of use, compatibility and performance, enabling us to separate the good from the bad. Since many smart thermostats have been on sale for some time, we regularly update our reviews to take into account the current market and new competition. In short, here you’ll find the best thermostats available today.

Know what you’re after? Skip on down to our list.

If you need a bit of help, here are the questions you should be asking yourself before you have a system installed, ensuring you choose the right product for your home and needs.

  1. What type of smart thermostat do you need? There are numerous smart thermostats to choose from, each offering a variety of features, so it’s important to pick the one that suits your lifestyle and home. First, you need to consider the type of heating system you want. A regular smart thermostat simply replaces your existing thermostat. You’ll still save money with such a system, but your heating settings will be applied to your entire home. A zoned heating system offers room-by-room control via smart thermostatic radiator valves (TRVs). Such a system will save you more money since you’ll be heating only the areas you’re using at any given time. The downside is that the initial outlay for such systems can be costly: typically around £50 to £70 per radiator. They’re a better option for houses with a greater number of rooms.
  2. What control options do I need? All smart thermostats should be controllable, to a degree, from the main unit as well as from a dedicated smartphone app. Voice control is becoming a more important feature, in the form of Alexa on the Amazon Echo or Siri using Apple HomeKit. Being able to simply tell your thermostat to turn the heating up or down is a convenient way to control the temperature in your home. Alexa support is more widespread, with HomeKit support lagging somewhat.
  3. Do I need “call for heat”? This is the ability, particularly for smart radiator valves, to turn on your heating when they’re too cold. An increasing number of smart radiator valves can’t “call for heat”. Instead, they offer finer control over a room’s temperature than a traditional mechanical thermostat, which will simply let you set your controls between one and five without giving you any indication what this means. Smart valves shut down radiators when the desired temperature has been reached. So, why would you want to go down this route? If you have an old boiler that you can’t upgrade, or you’re a renter who isn’t in control of overhauling the smart heating system, these options can be a helpful addition. And if you’re looking for greater control over an existing smart thermostat then such devices can be useful.
  4. Can they really save me money? In short, yes. According to Tado, UK customers can save up to 19% on heating costs in comparison to the costs of using a traditional dumb thermostat and normal heating controls, as our full guide to how much money a smart thermostat can save you explains.

Honeywell Evohome hero




Heating type: Smart thermostats and underfloor heating | Boiler connection: OpenTherm, On/Off | Hot water control: Yes | Geofencing: No | Smart assistants: Amazon Alexa, Google Assistant

The pros:

  • Extremely flexible
  • Touchscreen controller
  • Powerful Quick Actions

The cons:

  • No geolocation
  • Expensive

No company has as much experience in the heating arena as Honeywell, so it’s no surprise that its first smart product offering has been extremely comprehensive. Rather than replacing your basic smart thermostat, the Honeywell Evohome adds room-by-room control through smart TRVs, but also supports underfloor heating and even heat pumps.

Although this adds to the initial set-up cost – you’ll need a £59 TRV per radiator – it should save money thereafter, since you’ll only need to heat the rooms you’re using. Also, each room is set to its perfect temperature, making for a more comfortable home environment. You can even go beyond radiator control with support for underfloor heating and zone controls, too.

The level of control on offer is impressive, with the ability to set schedules per room. We love the Quick Actions, too, which let you make system-wide changes at the touch of a button, such as turning on the Economy mode (three-degrees colder in each room) to save money when you go out. There’s support for Google Assistant and Amazon Alexa, too. New this year is weather compensation, which can dial your heating up or down based on the temperature outside. It works brilliantly, making our home more comfortable.

Evohome continues to be a powerful multi-room system, ideal for larger homes featuring a range of heating sources.

Read our full Honeywell Evohome review

Nest Learning Thermostat 3rd Generation hero




Heating type: Single thermostat | Boiler connection: OpenTherm, On/Off | Hot water control: Yes | Geofencing: Yes | Smart assistants: Amazon Alexa, Google Assistant

The pros:

  • Looks fantastic
  • Learns how you use it
  • Sharp and clear display

The cons:

  • Can’t expand to radiator control

The Nest Learning Thermostat is among the best-known smart thermostats around, and for good reason. This product has shown how powerful smart heating can be. Now in its third generation, it remains one of the best smart thermostats you can buy.

As the name suggests, the thermostat learns how you like your home heated, using this information to create an automatic schedule for you. Not surprisingly, there’s an initial learning curve – in the first few weeks, the Nest may not work quite the way you want it to. Over time, however, it should prove more effective than a manually set schedule on rival thermostats. In addition, the thermostat uses presence detection to turn on and off automatically, depending on whether anyone is at home.

The Nest is brilliant at talking to other devices via the Works With Nest program, and a variety of other smart devices will interact with your smart thermostat, too. For example, your Philips Hue lights can turn off when you go out. With an excellent IFTTT channel and support for Amazon Alexa and Google Home (although HomeKit support doesn’t seem likely), the Nest is one of the best-connected smart thermostats available.

This latest version supports dual-zone plumbing and can be extended to support hot water systems as well. Note that there are no smart radiator valves to add full zoning, however.

Read our full Nest Learning Thermostat review

Genius Hub hero



Heating type: Smart thermostats and underfloor heating | Boiler connection: On/Off | Hot water control: Yes | Geofencing: No | Smart assistants: Amazon Alexa coming soon

The pros:

  • Extremely flexible and can handle multiple heating types
  • Super-quiet radiator valves
  • Motion sensors help control costs

The cons:

  • Better for larger homes
  • Currently no support for Amazon Alexa or Google Assistant
  • Slightly fiddly app control for overriding temperatures

If you’re looking for the most powerful and flexible heating system, then the Genius Hub should be top of your list. Designed and built by a UK company, this is a seriously impressive heating system that can control practically all types of heat source, from combi boilers to electric. As you’d expect from such a system, control over individual rooms comes courtesy of smart radiator valves.

Genius Hub goes further than the competition, thanks to its motion sensors. In the app, you can use the motion sensors to automatically set up a heating schedule via room occupancy (Footprint mode, which is free forever), or you can use the new Sense mode (subscription required) to set a schedule as standard; but you can also choose to use the motion sensor to only turn on the heat when there’s someone in the room. For example, you could set your living room to use the motion sensor during the day, so if you do have the day off work then your heating can be set to turn on automatically. That’s what we call smart.

There’s an Amazon Alexa skill, but no dedicated Google Assistant skill – although you can connect the system via IFTTT for some basic control here. A high price may put off some, but the Genius Hub system is designed for the largest homes or for those wanting the biggest savings. In our experience Genius Hub works brilliantly and is worth every penny.

Read our full Genius Hub review


Heating type: Single thermostat (optional smart radiator valves) | Boiler connection: OpenTherm, On/Off | Hot water control: Yes | Geofencing: Yes (via subscription) | Smart assistants: Google Home, Amazon Alexa, Apple HomeKit

The pros:

  • Excellent app
  • High-quality thermostat and radiator valves
  • Easy to programme
  • Clever energy saving

The cons:

  • Extension kit for hot water is expensive
  • Plug-in bridge seems superfluous
  • Have to pay or geolocation and open-window detection

Tado launched with the goal of making smart heating systems easy to use, and it certainly succeeded. The Tado Smart Thermostat is designed to track your location so that your heating goes off when you’re out and turns back on when you’re on the way home. It works brilliantly and has the most reliable presence detection we’ve tested.

Since launch, Tado has updated the apps and web interface to add a new heating scheduler, so you can choose the home temperature that you want hour by hour. There are also options for when you’re out – choose from maximum savings (which may mean you return to a colder home) or maximum comfort (you’ll spend more to keep your home warmer). The app is simple to use, making the Tado Smart Thermostat one of the easiest systems to program.

Tado’s system is also super-flexible. With the launch of its smart radiator thermostats, the system can be as powerful as Evohome’s. However, Tado’s radiator valves aren’t quite as smart, and the app’s zone handling isn’t quite as easy to use as that of Honeywell.

The addition of Amazon Alexa and Google Home support, IFTTT and HomeKit (via the V3+ internet bridge) make Tado’s Smart Thermostat one of the most powerful available. The downside is that the new system requires a monthly subscription to enable automatically turning off of the heating when you go out, plus the window-detection feature, which turns off the heating when a door or window is open.

By thinking of the subscription as payment towards ongoing development of the app and system makes it easier to accept. And you may decide you only need to pay for the extra features during the winter months, as you can cancel your subscription at any point.

Read our full Tado Smart Thermostat Review

Vestemi Radbot control



Heating type: Smart radiator valve | Boiler connection: None | Hot water control: No | Geofencing: No | Smart assistants: None

The pros:

  • Great value
  • Very little configuration
  • Easy to install

The cons:

  • No boiler control
  • No manual scheduling

Most smart heating systems require an app to provide fancy programming options. That’s all well and good, but it can make things complicated. The Vestemi Radbot is different: this smart radiator valve learns how you use a room automatically via its sensors, and then controls your heating automatically.

The Radbot looks like a standard TRV, and has a simple control dial that moves from 1 to 5 – these numbers correspond to a room temperature of between 15ºC and 24ºC. It would have been easier if Vestemi had put the temperatures on the dial, to be honest. But that’s our only criticism; otherwise, Radbots are brilliant.

The system learns how you use a room by tracking how light changes during the day – such as when you open the curtains, or turn the lights on and off. It turns the heating up when you’re in a room, and down when you’re not. And if you get cold, there’s a boost button. Even better, the Radbot works with your existing heating system, so there’s nothing to hook up to the boiler. If you want a smart solution that’s simple and cheap, this is the product for you.

Read our full Vestemi Radbot review 

Nest Thermostat E hero


Heating type: Single thermostat | Boiler connection: On/Off | Hot water control: No | Geofencing: Yes | Smart assistants: Amazon Alexa, Google Assistant

The pros:

  • Easy to install
  • Diffused screen helps thermostat blend in
  • Pre-programmed schedule

The cons:

  • Assisted install in-app can be finicky
  • No hot water support

Forget expensive installations and hassle – the Nest Thermostat E has been designed so that pretty much everyone should find it easy to install. The new Heat Link E battery-powered bridge attaches to the wires that were used by your old wired thermostat – and that’s it. Starting from scratch, most people should have the system up and running in under an hour. If you don’t have a wired thermostat, you’ll need to have the Heat Link E wired into your boiler, which will most likely mean a professional installation. While the system supports OpenTherm for increased energy savings, at this point your best option is probably a different product.

Nest has pre-programmed the Thermostat E with a schedule based on real data from existing Nest users. As you use the thermostat, it learns and updates your schedule.

The main thermostat has a diffused screen, helping it blend into the background. The screen displays the temperature, and you can use the outer dial to adjust it. The excellent Nest app provides even greater control, adding features such as geolocation to turn off your heating when you go out. True Radiant learns how your house warms up, so you can have it warm when you need to, and avoid overshooting your desired temperature.

If you’re looking for a simple, smart upgrade to an existing dumb, wired thermostat, then this is a great choice.

Read our full Nest Thermostat E review

Smart thermostats can be a minefield, with some potentially confusing details and information. Below you’ll find a bit more to help you get more out of the products.

Smart thermostat glossary: Here we round up all of the terms you’re likely to see, so that you can better understand which features you need.

What is OpenTherm?  A boiler technology that’s built to save energy by adjusting water temperature on demand, we explain what OpenTherm is and how it can help if you have a compatible thermostat.

What temperature should a condensing boiler be set at?  If you don’t have OpenTherm, you can save money by setting your boiler to the correct temperature. Follow this guide for the best advice.

How to save money with a smart thermostat:  Follow our advice to cut costs with your smart thermostat.

How to use a smart thermostat with an electric radiator:  If you want more control from an electric heater, this guide is for you.

  • Best smart heating system:  Honeywell Evohome
  • Best single smart thermostat: Nest Learning Thermostat
  • Best heating system for flexibility: Genius Hub
  • Best HomeKit smart thermostat: Tado Smart Thermostat
  • Best simple radiator upgrade: Vestemi Radbot
  • Best simple smart thermostat upgrade: Nest Thermostat E

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