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Best smart thermostats in 2021

Ecobee Smart Thermostat
(Image credit: Ecobee)

As the weather gets cooler, and you start using your heat more, it may be a good time to pick up one of the best smart thermostats to make sure you aren't burning money in your furnace. Among other things, a smart thermostat can detect when you’re not at home so no energy is wasted, but have it ready at the right temperature for when you return. 

Smart thermostats can be controlled straight from your smartphone, whether you’re out and about or having a lie down on the bed. They’re a great investment as they can save substantial money on your energy bill over time. But, which one should you choose? We’ve rounded up a list of the best smart thermostats. So, whatever your budget, there is one here for you. 

What are the best smart thermostats?

After hours of first-hand testing and comparison, we recommend the Ecobee SmartThermostat as the best smart thermostat overall. It stands out for featuring a wireless sensor which you can place in any room, ideally whichever takes the longest to heat or cool. Using this, you can set the Ecobee to continue running until that specific room has reached the ideal temperature. This sensor also features a motion detector, so if no one’s in the room, it won’t bother to heat or cool it. 

As it’s compatible with Alexa, you can also use Amazon’s voice assistant to control it. The speaker’s admittedly not as good as the Echo Dot, but it’s substantial enough that you can extend to Alexa in another room without needing to invest in another smart speaker. If you’re after privacy, you can also turn Alexa off if needed. If you're a HomeKit user, it's also compatible with Siri — though you'll also need a HomePod or HomePod mini.

If you want something with more of a premium feel, then the Nest Learning Thermostat is worth considering. The design is very user-friendly and it comes in a range of colors to suit your home including black, brass, copper, steel and white. Nest also offers remote sensors, but it’s worth noting that they don’t detect motion, unlike Ecobee’s. 

Amazon is coming out with its own Amazon Smart Thermostat, which costs just $59. However, it looks to be pretty basic, but will use Alexa hunches to try and adjust the temperature automatically based on your presence. It will be released on November 4.

Here are the best smart thermostats.

The best smart thermostats you can buy today

The Ecobee SmartThermostat on a wall

Ecobee SmartThermostat  (Image credit: Future)

1. Ecobee SmartThermostat

The best smart thermostat overall

Works With: Amazon Alexa, Apple HomeKit, Google Assistant, Samsung SmartThings, Logitech, Wink, IFTTT | Remote Sensors: Yes | Self-Installation: Yes | Motion Activation: Yes | Works Offline: Yes

Full Alexa support
Improved remote sensors from previous model
Plays Spotify through built-in speaker
Larger than Nest Learning Thermostat
Not as attractive as Nest

The best smart thermostat overall, the Ecobee SmartThermostat looks and acts much like the Ecobee4, but with a few big improvements. It's among the best Alexa compatible devices because it offers all of Alexa's features, including calling, messaging, and Drop-In. A recent update also lets you use it with Siri, though you'll need to also have a HomePod or HomePod mini on the same network.

The Ecobee also has a much better speaker than the previous version and Spotify support, so it's now good for playing tunes if you're looking for a device to provide some background music. To be sure, it's still far below even the Echo Dot in terms of quality, but it's an economical way to get Alexa in a room if you don't want to plug in another smart speaker. Most importantly, the new Ecobee has redesigned remote sensors that have much better range and battery life. We're not enamored with the Ecobee's looks, though; its plasticky design hasn't changed much since the original, and unlike the Nest, is beginning to look dated.

Read our full Ecobee SmartThermostat review.

The Nest Learning Thermostat v.3

Nest Learning Thermostat v.3 (Image credit: Nest)

2. Nest Learning Thermostat v.3

Nest's smart thermostat is a cinch to set up and has a classic design.

Works With: Amazon Alexa, Google Home, Logitech, IFTTT, Samsung SmartThings, WeMo, Wink, Xfinity | Remote Sensors: No | Self-Installation: Yes | Motion Activation: Yes | Works Offline: Yes

Large display
Works with multiple smart home systems
Easy to install
Can't monitor temperature in multiple rooms
Doesn't work with Apple HomeKit

The Nest Learning Thermostat was the original smart thermostat, and its classic design still stands out among the competition. The third version of this Google-owned thermostat has a larger and sharper display than its predecessor. Like before, the Nest Learning Thermostat learns your behavior over time, so it can automatically change the temperature when someone comes home. 

While the Nest thermostat has a retro-style circular design, its brushed stainless steel finish and turning mechanism all feel premium. Plus, it comes in a variety of finishes, including Brass, Polished Steel, Copper, and White, so it can more easily fit in with your home decor. This thermostat combines the best of the past with the future, and is one of the best smart thermostats that's Google Home compatible.

Read our full Nest Learning Thermostat review.

Honeywell RTH6580WF (Image credit: Honeywell)

3. Honeywell RTH8580WF Wi-Fi Thermostat

The best smart thermostat for those on a budget.

Works With: Amazon Alexa, Google Home, IFTTT, Samsung SmartThings, Wink, | Remote Sensors: No | Self-Installation: Yes | Motion Activation: No | Works Offline: Yes

Inexpensive
Works with a lot of smart home devices
Basic design

The Honeywell RTH6580WF Wi-Fi Thermostat is the best smart thermostat for those on a budget, because offers much of the same functionality as higher-end models, but costs less than $100. 

Like the Nest and Ecobee smart thermostats, you can control the Honeywell RTH6580WF from your smartphone, and connect it to Alexa and Google Assistant, which not only lets you change the temperature with your voice, but link it with other smart home products. In addition, the Honeywell Home ecosystem includes a wide range of partners, including Arlo, Apple HomeKit, SmartThings, Lutron, Kwikset Kevo, and more.

What you don't get with the Honeywell RTH6580WF are the stylish looks of the Nest, nor the remote sensor capabilities found with the Ecobee. But, if all you're looking for is a smart thermostat that delivers on the basics, this is a great model to consider. 

Read our full Honeywell RTH6580WF review.

The Nest Thermostat on a white background

(Image credit: Google Store)

4. Nest Thermostat

The best Nest thermostat for those on a budget

Works With: Amazon Alexa, Google Home, IFTTT, Samsung SmartThings | Remote Sensors: No | Self-Installation: Yes | Motion Activation: No | Works Offline: Yes

Inexpensive
Attractive
Easy to use
Lacks smarts of other Nest thermostats
Doesn’t work with remote sensors

The Nest Learning Thermostat is stylish and smart, but at $249, it's expensive. If you want a Nest-like experience for half the price, the simply named Nest Thermostat is the best option. While it doesn't have a rotating bezel, it does have an intuitive touch-sensitive strip along one side, and an attractive mirrored front that begs you to touch it (don't).

However, for the lower price, you are giving up two key features: This thermostat doesn't "learn" your patterns and adjust the temperature accordingly. Nor can it work with remote sensors, so it won't be as helpful if you have a room that stays particularly cold or hot. But for $129, the Nest Thermostat is priced to sell.

Read our full Nest Thermostat review

The Ecobee3 Lite smart thermostat

Ecobee3 Lite (Image credit: Ecobee)

5. Ecobee3 Lite

A simple smart thermostat that lets you use remote sensors.

Works With: Alexa, Google Assistant, Apple HomeKit, Samsung SmartThings, Logitech, Wink, IFTTT | Remote Sensors: Yes | Self-Installation: Yes | Motion Activation: Yes | Works Offline: Yes

Works with Amazon Alexa, Google Home, and Apple HomeKit
Attractive interface
Easy installation
works with remote sensors
Lacks geofencing

Like the 5th-generation Ecobee thermostat, but don't care for Alexa, and are looking for something less expensive? The Ecobee 3 Lite has many of the same features as Ecobee's top-end model, but costs $80 less.

The Ecobee 3 Lite has a color touchscreen, intuitive interface and deep smart home integration. Plus, Ecobee also updated the Lite model to work with remote sensors so you can set it to keep the heat on until a room in a far corner of your house reaches a certain temperature. However, you have to purchase those sensors separately.

The Ecobee 3 Lite works with Apple HomeKit, Google Assistant and Alexa, but unlike the Ecobee 5th gen, Amazon's voice assistant isn't built into the thermostat. It also doesn't support HVAC accessories, so you can't use it if, say, you have two-stage heating and cooling. It also lacks eco+, which learns your schedule and recommends changes to help save you money. 

Read our full Ecobee3 Lite review.

The Sensibo Sky with its box

Sensibo Sky (Image credit: Sensibo)

6. Sensibo Sky

An inexpensive way to make your window AC units smart

Works With: Alexa, Google Home, IFTTT | Remote Sensors: No | Self-Installation: Yes | Motion Activation: No | Works Offline: No

Easy to set up
Has robust scheduling, geofencing
Works with Alexa, Google Assistant and IFTTT
No controls or display on device

Most smart thermostats are designed for homes that have central heating and cooling systems, but what if you live in an older house or apartment, and rely on window air conditioners to keep things cool? There are a few companies that make smart thermostats for this purpose, and of them we think the Sensibo Sky is the best smart thermostat for those with in-wall or window air conditioners that have IR remotes. 

The Sensibo Sky is inexpensive, costing around $100, and was easy to set up, pairing with our window A/C unit in a flash. While the Sensibo Sky doesn't have any display to show the temperature, we liked its small, inconspicuous design. We also liked that it can be controlled remotely, and lets you create schedules for when they should turn on and off. It even has geofencing, so it can turn your AC on as you get home. Now that's cool.

Sensibo has a newer version, the Sensibo Air ($179), which also includes a motion sensor; this can be configured so that the Sensibo Air will turn off your air conditioner when no one is no longer present, and turn back on when someone enters the room.

Read our full Sensibo Sky review.

The Nest Thermostat E mounted on a blue wall

Nest Thermostat E (Image credit: Nest)

7. Nest Thermostat E

A lower-priced Nest smart thermostat

Works With: Alexa, Google Home, IFTTT | Remote Sensors: Optional | Self-Installation: Yes | Motion Activation: No | Works Offline: Yes

Cheaper than original Nest
Simple installation
Works with Alexa and Google Assistant
Does not support two-stage heating/cooling
White display can be hard to read

The Nest Thermostat E is another excellent smart thermostat for less than $200. It's easier to set up than the pricier Nest Learning Thermostat, but still has many of the same features. However, the Nest Thermostat E doesn't support as many HVAC systems, nor does it support such features as two-stage heating and cooling. For the majority of homeowners, this shouldn't be an issue. 

The Nest Thermostat E has the same shape as the Nest Learning Thermostat, but instead of metal, it's made from plastic. Additionally, the Nest Thermostat E only comes in white, rather than the multitude of finishes for the pricier Nest Learning Thermostat. Lastly, the Nest Thermostat E's all-white display can be hard to read from a distance. But, if you're looking for something a bit less expensive than Nest's premium thermostat, the Nest E is one to consider.

One thing to note: Google is no longer selling the Nest Thermostat E directly, but you can still find it at other retailers for around $169. 

Read our full Nest Thermostat E review.

The Honeywell Home T9 Smart Thermostat on a grayish wall

Honeywell Home T9 Smart Thermostat (Image credit: Honeywell)

8. Honeywell Home T9 Smart Thermostat

A smart thermostat with useful remote sensors

Works With: Alexa, Google Home, IFTTT | Remote Sensors: Optional | Self-Installation: Yes | Motion Activation: No | Works Offline: Yes

Responsive sensors
Easy to set up
Works with Amazon Alexa and Google Assistant
App could be more intuitive
No Apple HomeKit integration at launch

The Honeywell T9 incorporates what we think is one of the best features for smart thermostats: Remote sensors that can measure the temperature and see if there's a person present, so that the thermostat can better adjust your HVAC system to make sure all rooms are comfortable. You can purchase it with a remote sensor for around $199, or without a sensor for around $169.

Honeywell's T9 smart thermostat has a rectangular shape, which gives it a more modern appearance than, say the Nest. We also like its large, bright display that boldly shows the current temperature. 

The Honeywell T9 works with both Alexa and Google Assistant, and it has a geofencing feature, so that the thermostat knows when you're nearing home, and will adjust the temperature accordingly. However, the Honeywell app could be easier to use, and this smart thermostat doesn't support Apple HomeKit.

Read our full Honeywell T9 review.

How to choose the best smart thermostat for you

If you’re in the market for a smart thermostat, there are a number of factors you will need to consider, the first being cost. 

  • $200 plus: For this price, you will find the more premium models on offer including Ecobee and Nest. These will come with the most features and tend to look the most impressive as well. If your home has two-stage heating and cooling, then these will be the best smart thermostats for you. This is because lower value smart thermostats tend not to support more complex HVAC systems. 
  • $100-$200: Most smart thermostats will fall into this price range and their capabilities will be sufficient for most homes. Although, you won’t have access to some of the premium features such as voice assistants or two-stage heating.  
  • Less than $100: These models will cover the basics and can still connect to your smartphone. But, they’re not as easy on the eye.  

Another factor to consider is the size of your house and whether any rooms struggle to reach the ideal temperature. If this is the case, you may want to consider a model which comes with, or supports, a wireless sensor, such as the Ecobee. 

You should also look into other features of interest, such as geofencing, where you can set the ideal temperature for when you’re out of the house and for when you return. It’s also worth checking if the smart thermostat is compatible with Alexa and Google Assistant too.   

How we test smart thermostats

The best way to test a smart thermostat is to use it first-hand in your home, and that’s exactly what we do. We assess how easy it is to install and set up, which is important considering most smart thermostats are designed to be installed by the homeowners themselves.  

During the trial period, we put each smart thermostat through a set number of tests to see how it handles different situations. We consider how well it responds to changes in temperature and whether we can easily create a schedule. If it comes with an app, that’s also assessed for navigation and effectiveness. The same goes for connectivity to smart home hubs or devices; if it works with Alexa or Google Assistant, we check its performance there too. Any additional features are trailed as well so we can get a full picture of the product. 

How to install a smart thermostat

For the most part, installing a thermostat, smart or not, is a fairly easy process, usually involving nothing more than a screwdriver and about half an hour of your time. Here's our guide to how to install a Nest thermostat; however, the procedure is similar for almost any thermostat.

Mike Prospero

Michael A. Prospero is the deputy editor at Tom’s Guide overseeing the home, smart home, drones, and fitness/wearables categories, as well as all buying guides and other evergreen content. When he’s not testing out the latest running watch, skiing or training for a marathon, he’s probably using the latest sous vide machine or some other cooking gadget.

  • seoguy
    Archived comments are found here: http://www.tomsguide.com/forum/id-2611611/smart-thermostats-2015.html
    Reply
  • wolf39
    Sorry - it's simply not true that Ecobee can support multiple zones. IT definitely CAN'T! It supports multiple thermostats, however it is not able to control multiple zones, which makes multiple thermostats kind of obsolete and nonsensical (unless you want to raise room temperature everywhere if you for example your bedroom is too cold). If you need multiple zone control support you need to get evohome or tado.
    Reply
  • Carl_12
    Can we install a thermostat ourselves ??
    Reply
  • bukzin
    Yes, these are meant to be installed by homeowners.
    Reply
  • Nguyen_13
    thank for you sharing!
    Reply
  • SteveReeves
    I think the room sensors that allow for temp control in the room that you're in is great!

    I've seen some smart vents that close themselves off too.

    Wonder if Nest is doing anything to counter this in upcoming releases.
    Reply
  • gardavis
    The Ecobee3 Lite now can support the sensors. In fact, they have a promotion at the vendor's site that includes 2 sensors and the Lite for $169. Also, I don't think the display is color as you say.
    Reply
  • chumgrinder
    Our home has two independent HVAC units. Our power company just introduced demand pricing that makes it very desirable for us to ensure that only one unit operates at a time. I suspect there must be a thermostat product that allows two thermostats to coordinate such that they take turns. Can anyone recommend one?
    Reply
  • ctn.gooners
    Nest does not make a thermostat that controls the maintenance band and does not allow users to modify and adjust the band that is stuck at +/-1°F. If you have an old cast iron heater system, DO NOT BUY a Nest. It will force your system to start up Everytime it drops a degree, and initial start ups will use more natural gas, therefore Nest does not save money. Nor does do they offer any help to remedy or fix the problem.
    Reply
  • reidg99
    Mike, I see very little information about notifications due to a power outage. I’m considering a Honeywell smart thermostat because it’s monitored by an outside server. From what I was told by Honeywell support, if I have a power outage their server will notify me that the thermostat is offline. That’s important to avoid frozen pipes at second homes, in my case a ski camp, or a primary home should it be left during vacation or otherwise in the winter. This service/feature is not considered in any of the top rated or recommended thermostat articles I’ve read...but should be. With that said, are there other smart thermostats that meet the above requirements that I should consider.
    Reply