Best smart thermostat 2021 to help you stay warm and save money

The best smart thermostats and smart radiator valves from Nest, Hive, Tado and more

Included in this guide:

Best smart thermostat 2021, Nest Smart Thermostat E with stand on side table, next to a plant and notebook
(Image credit: Google)

Adding one of the best smart thermostats to your home helps it stay just the right temperature no matter what's going on outside – and they can save you energy and money while doing it, as a bonus.

The best smart thermostats can help keep you hot or cool as needed, but not just on a basic set schedule – you can control them remotely from the app, or you can use voice control from the best smart speakers, but even more importantly they can adapt and learn from your habits in real life.

If you keep tweaking it up in the evenings, it'll just change its routine so you don't need to in the future. And it learns how long it takes your home to heat up, so it can start heating up earlier on cold days to make sure it still hits the right temperature at the time you want.

When you're out on your travels, a capable smart thermostat will look at and analyse your routine, only heating up your home when you're actually in it (and perhaps on your way back to it as well). These gadgets are more clever than you might have realised if you don't already own one.

There's a top entry on our list, because there has to be, and it's not there for show: we really do think the Nest Thermostat E is going to be the best choice for most homes. That said, it may not be right for you – other options can make it more easy to create separate heating zones, where some rooms are heated at different times and to different temperatures than others.

As you go through our extensive guide, weigh up your options, the budget you've set yourself, and the specific kinds of automation you require, and that should lead you straight to the right smart thermostat for you. UK buyers might also like to take a look at our Nest vs Hive vs Tado guide, which compares three of the biggest ecosystems.

The best smart thermostats: our picks

Nest Thermostat E on white backgroundT3 Award

1. Nest Thermostat E

A brilliantly stylish, capable and affordable smart thermostat

Display: 81 mm x 81 mm, 320 x 320 pixel 24-bit colour LCD
Sensors: Temperature, humidity, near-field activity, far-field activity, ambient light
Connectivity: 802.11b/g/n Wi-Fi (2.4GHz/5GHz); 802.15.4 (2.4GHz); Bluetooth Low Energy (BLE)
Compatibility: Combi boilers; System and heat-only boilers; Domestic hot water tanks; Hydronic underfloor systems; Air-source and ground-source heat pumps (heating only); Zoned systems (one Nest Thermostat per zone); Heating systems with OpenTherm technology
Colours: white
Reasons to buy
+Smart Nest learning on board+Better value than the top-end Nest+Excellent mobile apps+Alexa and Google Assistant compatible
Reasons to avoid
-No HomeKit/Siri support-Not as premium look as regular Nest

If we were to be uncharitable, we'd describe the Thermostat E as a bargain-basement version of the Nest Learning Thermostat. There have been some obvious corners cut: the screen is a little more muddy, the case more plasticky and obviously cheaper, and there's less useful info displayed. But every one of those features is a nice-to-have rather than a must-include, and on balance the Nest Thermostat E is the better deal, premium feel or not.

It's the brains that make a thermostat, not the presentation, and this is perfectly fine in isolation, and it has all the smarts you'll need. You can always go for its more expensive cousin if you really want to wow guests with your thermostat.

You get all the smarts that are well-established in the Nest line, most impressive of which is the learning algorithm which works out both when you're home and when you like the heat a little hotter, helping to set the right temperature at the right time. This should save you money, since you won't leave it turned up by accident. It'll also tie in to individual temperature sensors, so you can make sure you're getting the heat you want in the right rooms and spaces. 

Unsurprisingly, the Thermostat E plays nice with Google Assistant, but Alexa users will be glad to know it works happily with that ecosystem too. It's not, however, compatible with Apple's HomeKit platform, and you won't be able to control it with a SmartThings hub either.

Neatly, Nest will send you a smart energy report every month, to show you just how active the thermostat has been, and give you a chance to tweak its settings if it looks like it's got the learning a little wrong. In terms of bang for your buck, this is the best smart thermostat of 2021. If you want more info about how it compares to the more expensive Nest thermostat, here's our Nest Thermostat E vs Nest 3rd Gen guide.

Tado Smart Thermostat on white backgroundT3 Award

2. Tado Smart Thermostat

Minimalist, efficient and easy to use

Display: 32x20mm LED matrix display, comprising 10x19 LEDs
Sensors: Temperature; Humidity; Ambient Light
Connectivity: 868MHz, Mesh (6LoWPAN)
Compatibility: Worcester, Baxi, Vaillant, Potterton, Ideal... ; Supports both 230V and extra low voltage interfaces (digital bus/analogue); Combi, system and heat-only boilers; Conventional and condensing boilers; Common Y-, S- and W-plan setups; Relay compatible, both switched live systems and potential free (dry contact) systems; Compatible with the UK standard backplate; Hydronic underfloor systems; Electric underfloor systems with a maximum switching current of 6A; Air source and ground source heat pumps (heating only); Zoned systems (one Smart Thermostat per zone)
Colours: White
Reasons to buy
+Easy to use thermostat and app+Geofencing capability+Works with 95% of central heating systems+Valves have a display too
Reasons to avoid
-Quite tech-y design-Monthly cost for geofencing and other features

Now on version three, Tado's thermostat is a refined little thing, and we have to say it's a  looker despite its more simplistic LCD display. It's hugely compatible, apparently happy to interact with some 95% of boilers on the market, and it works with just about everything: combi and conventional boilers, heated floors, hot water systems, the lot. Although we'd recommend you have a qualified engineer fit it, Tado suggests that the v3 can be installed by just about anyone within around an hour, so it's one to give a go if you're handy with a screwdriver.

It can work out the layout of your rooms and the heat capacity of your home, so if you're looking to hit a certain temperature at a certain time, it'll fire up your heat a little early to get to target temperature at the right time. There's also geofencing, so the Tado thermostat works in tandem with your phone to know when you're in range of home; after you've been out, it'll predict from your movements if you're on the way home and get things warming up in anticipation.

You can control it with the app (natch) which is a very good looking and well laid out thing, but there's also compatibility with all three major smart assistants. 

Tado isn't just the core thermostat, of course. Its capabilities can be extended with temperature sensors which you scatter around your home, and Tado's Smart Radiator Thermostats complete the package by allowing you to control the specific temperature in each room by tweaking radiator valves automatically. These are a competitor to Hive's equivalent product, and we've got a Hive Smart Radiator Valve vs Tado Smart Radiator Thermostat comparison.

Nest Learning Thermostat on grey backgroundT3 Award

3. Nest Learning Thermostat

Smart, easy-to-use, and surprisingly sexy

Display: 5.3cm, 480x480, 229ppi LCD
Sensors: Temperature, Humidity, Near-field activity, Far-field activity, Ambient light
Connectivity: 802.11b/g/n Wi-Fi (2.4GHz/5GHz); 802.15.4 (2.4GHz); Bluetooth Low Energy (BLE)
Compatibility: Combi boilers; System and heat-only boilers; Domestic hot water tanks; Hydronic underfloor systems; Air-source and ground-source heat pumps (heating only); Zoned systems (one Nest Thermostat per zone); Heating systems with OpenTherm technology
Colours: Stainless Steel; Copper; Black; White
Reasons to buy
+Easy to use+Learns as you go+Can be controlled from your tablet or smartphone+Cost includes expert installation
Reasons to avoid
-No HomeKit/Siri support

Nest takes Apple-like care in its product design (it was founded by ex-Apple employees), and it's definitely one of the better-looking smart thermostats out there. In fact the Nest is largely responsible for kick-starting this whole smart home category.

This 3rd-generation Nest Learning Thermostat is able to monitor your habits and control the heating accordingly. So, for instance, if regularly go to bed at 11pm or so, the system learns from that and starts turning the system off around that time. Before long you're saving money and you don't even have to touch the Nest.

Another smart feature the Nest brings to the party is an on-board activity sensor that can take an educated guess as to whether anyone is at home or not, and then adjust the heating schedule accordingly. If you want to take more manual control, over when the heating starts and stops, then the Nest is easy to schedule using the accompanying app.

That circular glass interface is beautiful to behold and so incredibly simple use – all you require is an opposable thumb and a forefinger. While the Nest Learning Thermostat comes with everything you need to fit it, we'd say you're better off having an engineer do it, especially as the price includes installation.

With the Nest Thermostat E delivering essentially the same performance and functionality but for a much cheaper price point, potential buyers should evaluate just how much they desire the more premium aesthetic, though. Still hands down one of the best smart thermostats right now. You can see how it compares to some of the biggest competition directly in our Nest vs Ecobee and Nest vs Honeywell guides.

Hive Heating Control on grey backgroundT3 Award

4. Hive Active Heating 2

Smart, stylish and expandable, this is one of the best smart thermostats on the market

Display: 100 mm x 104 mm
Sensors: Temperature
Connectivity: Wi-Fi, Zigbee
Compatibility: Most gas, LPG, oil and electric boilers
Colours: 12+ frames sold separately
Reasons to buy
+Modern, minimalist design+Extensible with Hive smart home products+You don't have to be a British Gas customer to buy it
Reasons to avoid
-App is fiddlier than some

Hive is developed by British Gas, but you don't have to be a British Gas customer to use it. This excellent system is fitted by a qualified engineer, and includes a boiler receiver, an internet router hub, and a wall-mounted thermostat — which may not be quite as handsome as the Nest, but which is still easy on the eye. It's undoubtedly one of the best smart thermostats out there.

Perhaps more importantly, the whole system is ridiculously easy to use, whether you're operating the console itself or using the accompanying apps for iOS or Android. You can change the temperature or thermostat schedule from anywhere, automatically set the heating to turn off when you leave the house, then have it automatically turn back on again when you come home.

This works via location tracking in the app and it's the same for all the members of the household, if they're all happy installing the app – it means the rest of your family won't suddenly be plunged into freezing temperatures just because you've popped to the shops, which is obviously something you want to avoid.

The system is expandable too. Hive has released a range of compatible products, including sensors and plugs, so all your devices will talk to each other – you have the option of paying outright or via subscription, which gives you ongoing user support too. As an added bonus, you get support for Amazon Alexa and Google Assistant with Hive too, so it really earns its place on our list of the best smart thermostats of 2021.

Drayton Wiser Thermostat on white backgroundT3 Award

5. Drayton Wiser Thermostat

One of the best smart thermostats for value for money

Compatibility: Conventional boiler systems with separate water tanks
Colours: White
Reasons to buy
+Separate room control+Choice of packages
Reasons to avoid
-Lacking some more advanced features

Without packing in too many extra bells and whistles, the Drayton Wiser Thermostat system offers one of the best smart thermostat options in 2021: intelligent control of temperatures from your phone, and separate radiator valves.

That means you can customise the heating in each room if you need to, and the app gives you a choice of preset modes to pick from if you don't want to spend too long configuring everything. Amazon Alexa and Google Assistant support is included here as well.

While it doesn't have the same kind of brand recognition as something like a Nest or a Tado, the Wiser systems do a lot of the same jobs for a very appealing price, and are definitely worth considering.

We especially like the way you can start off small with radiator thermostats, and then add more as needed: you get a level of control and fine-tuning that not all the devices on this list can match.

There are small things that hint at where the experience isn't quite as slick as the likes of Nest of Tado – for example, geofencing is done through IFTTT, rather than directly, making it more complicated to set up – but for those who want the both smart features and multi-zonal control for a lower price, it's a really strong option.

Ecobee SmartThermostat with Voice Control on white backgroundT3 Award

(Image credit: Ecobee)

6. Ecobee SmartThermostat with Voice Control

Comprehensive smart home heating - now with Alexa Built-in

Display: 109 mm x 109 mm
Sensors: Temperature, humidity, occupancy, proximity
Connectivity: Wi-Fi
Compatibility: Gas, electric, oil, dual fuel
Colours: Black
Reasons to buy
+Support for up to 32 sensors+Simple and easy to use+Alexa, Google Assistant, HomeKit compatible
Reasons to avoid
-Thermostat is really big

While we may have previously directed you to the Ecobee4, the company's new smart thermostat (also called the Ecobee5 in some places) has rightly ousted it from our best smart thermostats list - not because this new model is radically different, since it looks similar and acts almost identically to its predecessor, but because it includes a whole lot more.

For a start, this is an Alexa device, and one which offers the full range of Alexa features, meaning it doesn't miss out things like drop-ins, calling or announcements - very unusual outside of Amazon's tight Echo ecosystem, but something we'd like to see more of. It carries a solid speaker, too - not world-beating, of course, but enough to get some tunes running (there's Spotify Connect support) if you're not too worried about them reverberating through your wall and annoying your neighbours.

There are also newly revamped smart sensors to go around your home, which up the range and boost the battery life, so they're pretty much just set-and-forget. It'll hook up to every major assistant, too. 

The only real issue might be getting hold of one - at present Ecobee focuses its business mostly on the US and Canadian markets, but previous models have seen release elsewhere. So keep your eye on sites like Amazon, or more likely on specialist heating retailers, if you live outside those regions and aren't interested in a potentially costly import. Our Ecobee vs Honeywell guide compares this option to its big-name rival directly.

Honeywell Lyric T6/T6R on white backgroundT3 Award

(Image credit: Honeywell)

7. Honeywell Lyric T6/T6R

Easy-to-use smart thermostat – with limitations

Display: not stated
Sensors: Temperature
Connectivity: Wi-Fi
Compatibility: Heating systems with OpenTherm technology; Common Y- and S-plan setups
Colours: not stated
Reasons to buy
+Easy to use+Geofencing works well+Apple HomeKit and Amazon Alexa compatible
Reasons to avoid
-Needs professional installation-Limited programming options

Looking like a cross between the British Gas Hive and the Nest from Google, the Lyric T6 is the latest in a long line of smart connected devices from the highly-regarded Honeywell with wired (T6) and wireless table-top (T6R) versions available.

The Honeywell Lyric T6/T6R can be controlled either via its touchscreen or via the free Honeywell Lyric smartphone app, with built-in geofencing so the system automatically knows to switch on and off depending on how close you (or other members of your household) are to home. It also works with Amazon's Alexa and is Apple HomeKit ready.

As with other smart thermostats, the Honeywell Lyric T6 is best fitted by a professional installer, since the supplied box that connects to your boiler (or second zone) needs to be connected to the mains. Once installed and set up, however, the system is easy to use — although there are some limitations.

While you can use either geolocation or a range of programmable modes to configure the heating, you can't use both these options together – a shortcoming the Tado, for example, doesn't have. That said, we do like is the Lyric's Optimised Start mode, which automatically fires up the heating early so your home is already add the right temperature when you wake up — just the job for those cold winter mornings.

Honeywell Evohome on white backgroundT3 Award

8. Honeywell Evohome

One of the most comprehensive smart thermostat systems around

Display: not stated
Sensors: Temperature
Connectivity: Wi-Fi
Compatibility: Gas, fuel, wood and electric boilers, heat-pump, zone valve, radiators, underfloor heating
Colours: White
Reasons to buy
+Learns as it goes+Supports a wide range of heating systems+IFTTT and Alexa integration
Reasons to avoid
-Not very nice to look at

Want to see another Honeywell system in our best smart thermostats list? Oh, go on then – the Honeywell Home is older and simpler than the newer Lyric models, but where it really excels is in the zonal control it offers.

You get individual thermostats for each radiator in the home, and a TRV valve is required in each case. Setup is easy on the radiator side though a little complicated when it comes to hooking up the boiler — it's best getting a professional in to do the job.

Design-wise, it's not going to win any awards, but it does the job of giving you more control over how and when your home gets heated. Each thermostat can be on a separate schedule, and the monitor is very straightforward to use.

As an added bonus, you can actually take the monitor device around the house with you for brief spells before returning it to its dock. For individual room and zone control, it's one of the best smart thermostats around.

Vaillant vSMART on white backgroundT3 Award

(Image credit: Vaillant)

9. Vaillant vSMART

Vaillant's own-brand smart thermostat is a great choice - at least for Vaillant boilers

Display: LCD
Sensors: Temperature
Connectivity: Wi-Fi, Alexa, IFTTT
Compatibility: Vaillant boilers
Colours: White
Reasons to buy
+Learning functionality+Weather compensation+Good connectivity
Reasons to avoid
-Lacks some sensors

If you ask T3's resident gas fitter, there's no competition in the boiler market: they'll only install Vaillant. Whether there's some commercial interest involved in their enthusiasm we don't know, but we'd be remiss if we didn't follow the thread and look at Vaillant's own smart thermostat, the vSMART.

It does tick all of the key boxes: there's an app for both iOS and Android, there's Alexa compatibility (though no Google Assistant), there's integration with IFTTT so you can set up more complex automations. It's brainy enough to learn your patterns, working out when you like to turn the heat up and when you prefer it cooler. The vSMART can also keep tabs on your local weather, helping it to know when to boost itself in order to hit your desired temperatures faster, or switch to a holiday mode to stop your home freezing while you're away while using minimal energy.

A good choice for Vaillant boilers, then, but do bear in mind there are a few features missing that other thermostats offer. There are no remote sensors for example, so you'll be stuck with setting the temperature based on whichever room the thermostat itself is in, and that thermostat unit doesn't have the person-sensing brains of, say, the Nest.

Heatmiser Neo Best on white backgroundT3 Award

11. Heatmiser Neo

HomeKit-compatible, but needs pro installation

Display: Blue backlit screen
Sensors: Temperature; Air
Connectivity: Wireless Mesh Network (via neoHub)
Compatibility: not stated **Colours** Sapphire Black; Glacier White; Platinum Silver
Reasons to buy
+Easy to use smart thermostat and app+HomeKit compatible+Includes geofencing
Reasons to avoid
-Professional installation needed-Options list can be confusing

This intuitive zonal system is similar to the Heat Genius we mentioned above, only it's fully wired, which means a) installation should be carried out by a pro (like many other units here) and b) your walls will likely need to have conduits installed.

It's a much more baffling system to get one's head around, mind, since there's a bewildering assortment of different mix-and-match options available. In this respect you're advised to contact Heatmiser direct to discuss your needs. If you can make sense of the various combinations — and it is possible — this could be the best smart thermostat solution for you.

A wireless version of the Heatmiser system (which we haven't had a look it) is  also available in kit form. Dubbed, the neoAir Kit Gen 2, it comprises a neoAir smart thermostat, a second-generation neoHub and an RF switch and is capable of being DIY installed. If you find the wired Heatmiser Neo a little overwhelming, consider the wireless alternative.

Both wired Neo and wireless NeoAir versions are Apple HomeKit compatible, so you can use them as part of your Apple-run smart home. The Heatmiser kit looks good, works well, and is flexible enough to be able to adapt to most home scenarios — just don't be afraid to ask for advice about which setup is best.

How to buy the best smart thermostat for you

There aren't a host of specs to sift through when choosing the best smart heating thermostats for 2021, because they all work along similar lines – but there are some purchasing points to make. Compatibility with other smart home kit is one important consideration to weigh up, for example, as it's a very good idea to make sure your new thermostat is going to work with your existing smart home devices.

In other words, if you're already controlling most of your smart home kit through Amazon Alexa, it makes sense to buy a smart thermostat that's also Alexa compatible, rather than suddenly switching to Google Assistant.

We'd also recommend checking with your energy company to see if any smart thermostat deals are on the table: it might discount the price of certain models, or maybe even give you one for free.

Apart from that, the right device for you will be one that adapts to your home's routine and starts saving you cash (by intelligently setting temperatures) as quickly as possible, and the associated app and platform can help here. 

You can even use smart thermostats to create zonal heating in your home – many of the devices we've listed support existing zonal setups, but there are also options such as the Tado Smart Radiator Thermostat that enable you to control each radiator individually, so your colder rooms can get relatively more heating time.

David Nield
David Nield

Dave has over 20 years' experience in the tech journalism industry, covering hardware and software across mobile, computing, smart home, home entertainment, wearables, gaming and the web – you can find his writing online, in print, and even in the occasional scientific paper, across major tech titles like T3, TechRadar, Gizmodo and Wired. Outside of work, he enjoys long walks in the countryside, skiing down mountains, watching football matches (as long as his team is winning) and keeping up with the latest movies.