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Best smart thermostat 2021: ranking the top smart thermostats we’ve tested

Best Smart Thermostat
PRICE
VERDICT
REASONS TO BUY
REASONS TO AVOID
VERDICT
REASONS TO BUY
REASONS TO AVOID

The best smart thermostats allow you to control heating and cooling your home from your smartphone, even when you’re not at home  - putting an end to the frustration of returning home late to find you’ve wasted energy because the heating has been running full blast all evening. 

One of the best smart speakers or smart displays on the market can also be used to control your smart thermostat, so you don’t even have to leave the sofa to ensure your home is at the perfect temperature for you. 

The best smart thermostats employ AI to identify how long it takes your home to heat up or cool down, amending your schedule accordingly so you use as little energy as possible - potentially saving you money (see below). Others offer room-by-room temperature control or can detect if you've opened a window and turn the heating off.  

However, with so much choice when it comes to easy-to-use and efficient internet-controlled heating systems, how do you know which will turn up the heat for you?  We’ve tested smart thermostats from Nest, Tado, Ecobee, and more. Read on to find out what we thought and decide which is the best smart thermostat to suit you. 

UPDATE: Ecobee has become one of the first smart home device manufacturers to reveal it’s bringing Siri to its new and existing smart thermostats that offer voice control. An update, which will be made available later this year, will ensure homes with a compatible Ecobee smart thermostat and an Apple HomePod or HomePod Mini in their home, will be able to say “Hey Siri” to their thermostat to get Apple’s voice Assistant to spring into action. Siri on Ecobee will be able to adjust the temperature, set timers, and even offer up personal requests such as checking your calendar entries.  

The best smart thermostats 2021: ranked

Nest Learning Thermostat

1. Nest Learning Thermostat

The best smart thermostat you can buy

Specifications
Dimensions: diameter: 84mm, height: 31mm
Screen: 24-bit color LCD, 480 x 480 resolution
Sensors: 10 temperature sensors, indoor humidity, proximity, near-field activity, far-field activity, ambient light
Zonal control: no
Connectivity: Wi-Fi, Wireless Interconnect, Bluetooth Low Energy
Reasons to buy
+Intelligent +Beautiful design
Reasons to avoid
-No zonal control-Doesn't work with Apple HomeKit

Nest is one of the biggest names in the smart home market, and for good reason. This Google-owned company delivers well-designed, easy-to-use products that are packed with serious smarts. 

The Nest Learning Thermostat (third generation) is renowned for its ability to learn your routines and adjust itself accordingly. This means that over time your heating system can actually adapt to suit your needs, without you having to do anything. 

It also benefits from location-based features that track where your phone is, and will turn the heating on or off depending on your location. But don't worry that it's going to turn off the heating and leave your guests to freeze when you're out, as its built-in sensors enable it to detect whether there's anyone at home. 

The main criticisms of the Nest Learning Thermostat are that it doesn't offer zonal control, and that if you're a tech novice it can be a little complicated to set up and use. The absence of zonal control means that while you'll be able to digitally control your property as a whole, you'll still have to manually adjust individual radiators. 

That said, if you're looking for a top-of-the range system Nest is a good way to go. Plus, with Google behind it, Nest is a good system to invest in if you're planning to build a wider smart home setup.

Read the full review: Nest Learning Thermostat 3rd generation


Hive Active Heating 2

2. Hive Active Heating 2

(UK only) The best smart thermostat for a single ecosystem

Specifications
Dimensions: 100 x 100 x 48mm
Screen: 3.5-inch color TFT display, 320 x 480 resolution
Sensors: Temperature
Zonal control: with Active Heating Multizone
Connectivity: Zigbee HA 2.0
Reasons to buy
+Beautiful design+Easy to use
Reasons to avoid
-Needs to be professionally installed -Doesn't work with Apple HomeKit

Hive is owned by Centrica, one of the UK's leading energy providers, so you can rest assured that you're in experienced hands when it comes to your heating needs.

The thermostat itself is a collaboration between Hive and Swiss designer Yves Béhar, who's responsible for everything from the August smart lock to PayPal's brand identity. That top-quality styling makes the Hive Active Heating thermostat something you'll be proud to have on your wall.

What's more, Hive has an excellent ecosystem, so you're able to control a vast range of Hive products using a single app. And its thermostat is no slouch, garnering our 'recommended' tag thanks to its simple interface and easy voice assistant integration. 

It's worth noting that, like the Nest thermostat above, Hive Active Heating doesn't support Apple's HomeKit, so it's best avoided if you're already invested in Apple's smart home ecosystem. 

With a small dial in the middle of its compact design controlling temperature, the Hive Active thermostat gives you the option of keeping things extremely simple, while being packed with features for those who want greater control of their system. 

Read the full review: Hive Active Heating 2

Honeywell Evohome

(Image credit: TechRadar)

3. Honeywell Evohome

The best smart thermostat for zonal control

Specifications
Dimensions: 139 x 101 x 21mm
Screen: 24-bit color LCD, 480 x 272 resolution
Sensors: temperature sensor
Zonal control: yes
Connectivity: Wi-Fi, Bluetooth
Reasons to buy
+Incredibly simple controls+Great zonal control
Reasons to avoid
-Expensive-Not the most aesthetically pleasing

The Honeywell Evohome gives you total control over your home, with individual thermostats for each radiator enabling you to set an independent heating schedule for every room in your house.

It's difficult to grasp what a difference this feature makes until you've tried it for yourself. If you live in a house where different inhabitants prefer a different temperature, or if one room always seems to be hotter or colder than the others, this system is going to be a godsend.

What's more, it works with under-floor heating too, so even if you have a large and complicated heating system the Evohome gives you total control over all of it via an app that's a pleasure to use. 

The control panel and radiator thermostats aren't going to win any awards for design, coming as they do in plain white plastic, but that's not really the point of the Evohome. It's a simple system, without the bells and whistles of the Nest or Hive, but if you've got a complicated heating system that you want to control digitally, it's hard to beat.

Read the full review: Honeywell Evohome

Tado Smart Thermostat

4. Tado Smart Thermostat

The best looking smart thermostat

Specifications
Dimensions: 104 × 104 × 19mm
Screen: LED matrix
Sensors: temperature sensors, indoor humidity, ambient light
Zonal control: yes
Connectivity: via Tado Internet Bridge connected to router using ethernet port
Reasons to buy
+Sleek design+Zonal control
Reasons to avoid
-App is difficult to use-LED matrix screens  

The Tado Smart Thermostat should be brilliant. It offers the zonal control of the Honeywell Evohome, a slick design that rivals the Hive, and the geofencing smarts to match the Nest, but somehow it doesn't quite manage to pull all these features together into a cohesive system.

It's seriously good-looking – by far the most attractive zonal control on the market – but the app is unintuitive to navigate, and compared to the incredibly user-friendly app on the Evohome, it's positively difficult.

That's not to say it's a bad system – it's still comfortably a 4-star product, and we don't imagine anyone who buys the Tado regretting their purchase. And it's so close to being the perfect system – the one that mixes together the best features of other offerings. The problem is, it just doesn't manage to outshine any of its rivals.

One thing that does make the Tado stand out in this list is Apple HomeKit integration – if you're the proud owner of a HomePod, or you're firmly entrenched in the Apple ecosystem, this is probably the best smart thermostat for you. 

It's also worth noting that the things keeping Tado from standing out are all software rather than hardware issues, so these could well be addressed over time. The Tado Smart Thermostat isn't currently available in the US, but as Tado's Cooling system is sold there we'd be surprised if it didn't become available at some point. 

Read the full review: Tado Smart Thermostat

Nest Thermostat E

5. Nest Thermostat E

The best affordable smart thermostat

Specifications
Dimensions: diameter: 81mm, height: 29mm
Screen: 24-bit color LCD, 480 x 480 resolution
Sensors: temperature, humidity, proximity, ambient light
Zonal control: no
Connectivity: Wi-Fi, Bluetooth Low Energy
Reasons to buy
+Cheap compared to original Nest+Super-smart 
Reasons to avoid
-Not universally compatible-Plastic screen can be hard to read

If you like the look of the Nest Learning Thermostat but don't fancy shelling out the money for it, there's a cheaper alternative. It definitely looks cheaper – it's made of white plastic, with a white coating on the plastic screen that can make it hard to see the information being displayed – but it does echo the design language of the original Nest Thermostat, so you'll be more than happy to have it on your wall.

As the Nest's smaller sibling it benefits from industry-leading smarts, lacking only the most advanced features of the premium model which most users are unlikely to take advantage of anyway. 

The Nest E is a great example of how to streamline a flagship product to make a cheap alternative without damaging the qualities that made the original great. Make no mistake, this isn't flagship quality for bargain price, but it's great value for what it is.

Read the full review: Nest Thermostat E

Drayton Wiser smart thermostat

(Image credit: Drayton)

6. Drayton Wiser

(UK only) The best affordable smart thermostat for zonal heating control

Specifications
Dimensions: 76 x 76 x 25mm
Screen: 24-bit color LCD
Sensors: temperature, humidity, open-window
Zonal control: yes
Connectivity: Wi-Fi, Bluetooth
Reasons to buy
+Good zonal controls+Alexa and Google Assistant integration
Reasons to avoid
-Cheap design-Temperature isn’t visible from radiator thermostats

Love the idea of zonal heating control, but you're on a budget? Then Drayton Wiser is worth considering. 

The starter kit comes with the boiler module, a room thermostat, and two smart radiator thermostats, which replace any existing TRVs (thermostatic radiator valves) on your radiators, allowing you to control each radiator individually via the Wiser app. You'll need a thermostat for each radiator in your home to get the most out of the system, but as thermostats are around a third cheaper than rival systems from Honeywell and Tado, it makes the overall cost more affordable. 

It's simple to use and will switch the boiler on or off earlier than scheduled to ensure rooms in your home are at the temperature you want, when you want them. It's also got Open Window Detection to help stop energy wastage by switching off the boiler if it detects a window has been opened. 

However, it's not the most stylish of thermostats on the market, and there's no way to see the temperature of the room from the radiator thermostat itself  - you'll need to open the app on your smartphone. That said, it's hard to beat if you're on a budget and want full control over your heating.

Read the full review: Drayton Wiser 

Ecobee4 Smart Thermostat

(Image credit: Ecobee)

7. Ecobee4 Smart Thermostat

(US Only) The best smart thermostat with Alexa built-in

Specifications
Dimensions: diameter: 109mm, depth: 26mm
Screen: 3.5” full-color LCD touch screen, 320 x 480 pixel display
Sensors: temperature, humidity, proximity, ambient light
Zonal control: no
Connectivity: Wi-Fi, Bluetooth Low Energy
Reasons to buy
+Amazon Alexa built-in+Easy installation+Very well supported
Reasons to avoid
-Not widely available

If it's available where you live, the Ecobee4 is well-worth auditioning for your smart home setup. Like other smart thermostats on our list, you can control the Ecobee4 using a smart speaker or smart hub – but, unlike any of the other entries, the Ecobee4 comes with Alexa built right in.

That means, not only is it a great thermostat that can save you bundles on your energy bill each month but it doubles as a conduit to Alexa and its 10,000-strong library of skills. Besides being able to order pizza (yes, really) the Ecobee4 can be controlled wherever you are in the world – should, say, you forgot to turn that thermostat off before your international flight.

While Ecobee may not have the same clout that Nest has garnered in the last few years, it remains one of the best thermostats on the market, bar none.

Ecobee3 Lite Smart Thermostat

8. Ecobee3 Lite Smart Thermostat

(US Only) The best affordable Ecobee smart thermostat

Specifications
Dimensions: diameter: 109mm, depth: 26mm
Screen: 3.5” full-color LCD touch screen, 320 x 480 pixel display
Sensors: temperature, humidity, proximity, ambient light
Zonal control: no
Connectivity: Wi-Fi, Bluetooth Low Energy
Reasons to buy
+Great smart thermostat+Easy installation 
Reasons to avoid
-No Alexa built-in-No room sensors

OK, so not everyone needs another device with Alexa built-in. (We get it, guys, you can build Alexa into anything!) If you're in the camp of people with too many Alexa devices, the Ecobee3 Lite is the perfect solution - it's just the smart thermostat without the smart assistant. 

Now, that said, the Ecobee3 is still compatible with all the leading smart home ecosystems. (Ecobee was the first smart thermostat compatible with Alexa, believe it or not.) But if you want the all the extras, like room sensors that can detect temperatures in certain spots in your home, you'll have to buy them separately.

How do smart thermostats work?

Smart thermostats connect to your home Wi-Fi network and ensure an app on your smartphone, or a voice assistant, can be used to switch your home’s heating and cooling system, even if you’re not at home.

As well as adjusting the temperature in your home, most smart thermostats also enable you to set schedules, provide a report charting your energy use and even stop your heating coming on at all, for example because you’re heading out of town. 

Like most home smart home gadgets, smart thermostats can also be used in home automations that see other smart home gadgets, such as smart lights and smart plugs, controlled at the same time. So you can turn the heating up, dim the light and watch your favorite TV show with one command.

Do smart thermostats save money? 

Many smart thermostats make bold claims about how much money you can save, although energy saving standards firm Energy Star estimates having a smart thermostat installed will use  around 8% less energy a year, equating to $50 in the US - although this will differ in other territories. 

How you use your heating and cooling system will affect just how much of a saving you make. If you have it running all the time, then chances are you’ll generate some hefty savings, but if you already use a schedule to adjust the temperature in your home, the savings won’t be as big, but every little helps.