Best smart thermostats of 2021


A smart thermostat can give you remote control over your heating and air conditioning, making sure your home is as cool or toasty as you like when you get home from work or wherever else, and a great one can monitor environmental conditions and your own preferences over time, adjust your systems to keep you comfortable and save you money.

That’s why we spent the last several months testing seven smart thermostats to find the best one for your place.

Best overall smart thermostat

The Nest Learning Thermostat studies your habits and controls the temperature in your home automatically. These smarts, along with the simple interface, make it best in class.

Best budget smart thermostat

The inexpensive Nest Thermostat has the same simple interface and straightforward remote control options as it’s bigger sibling, but can’t learn your routines.


After months of testing across various models, the Nest Learning Thermostat never failed to impress. It has the most intuitive controls for when you do need to interact with it, along with smart features that let you set it and forget it. The Nest Learning Thermostat has more intelligence than the average smart thermostat; as you make temperature adjustments day in and day out, it learns from them and uses that to establish trends.

In our testing, after a week of use in the early summer, the Nest Learning Thermostat had figured out that we liked it a little cooler overnight and warmer throughout the day, and through it’s geofencing capabilities it figured out that it could switch to Eco when we left the house and then have it prepared for the time when we typically arrived back. Pretty neat, right? And that’s the real catch with Nest Learning Thermostat. It works to establish these patterns, adjust accordingly and ultimately possibly reduce the cost of your HVAC and electricity bill.

Beyond the smarts, the Nest Thermostat has three modes — cooling, heating and eco, which are accessible automatically or manually. Eco sets a temperature that might be a little hotter or a little cooler than your preferred, but engaging it when you’re out or when you might not notice it can reduce the cost of running the entire system. It’s quite handy. And if you ever want to override the temperature, it’s just a twist away.

The physical design of the Nest Learning Thermostat — the best user interface of any of the smart thermostats we looked at — makes that easy. The bezel is like a larger click wheel. You can turn it toward the right to raise the temperature or toward the left to lower it. It glides and is just built incredibly well. You can physically push in the bezel or the face to select an item as well. It’s got a high-end feel, as you’d expect given the $249.99 price tag. It feels great to use, and it’s just super intuitive to get the results you want.

When you don’t want to get up to adjust the temperature or mode, you can open the Nest app on your Android or iOS device. The app has an intuitive interface that mirrors the physical Nest Learning Thermostat. You can easily adjust the temperature, see historical performance or create your own schedules.

The Nest Learning Thermostat can also integrate with multiple temperature sensors throughout your home to better tailor heating and cooling for the entire space. Even in a single zone setup (as in our testing), the multiple sensors spread across three levels helped the Nest see the temperature more accurately throughout the space, and thus make more appropriate settings.

Lastly, let’s hit on installation: The Nest Learning Thermostat works with a broad range of HVAC systems. We tested it in two locations, a one-bedroom apartment with one zone and a three-story home with one zone, both equipped with a central cooling and heating solution that doesn’t feature a “C,” or common, wire. The C wire is typically used to deliver power to run a thermostat directly from house current. If your home doesn’t have a C wire (some more modern systems don’t use them) the Nest Thermostat can run on its integrated battery or from an optional power adapter if your HVAC system is particularly power-hungry.

Before starting the installation, we ensured that our HVAC system was turned off at the breaker, removed the old thermostat, hooked up the Nest Thermostat with the proper wiring configurations and connected it via the Nest app (available for Android or iOS). The app checked our handiwork, and we were off to the races.

In our extended testing, the Nest Learning Thermostat has kept us comfortable, and it’s always looking to improve. Those smarts, paired with an intuitive design, make it the best smart thermostat out there.

Jacob Krol/CNN

For those on a tighter budget, the $129.99 Nest Thermostat gives you the well-designed interface and remote app controls of its big sibling but forgoes the integrated intelligence.

You can still switch manually between modes (cool, heat, cool and heat, Eco mode or off), quickly enable a preset, set a schedule and control the fan (depending on the configuration of your HVAC system, of course). The Nest Thermostat, however, will not learn your preferences over time like the Nest Learning Thermostat. It can’t log your usage and work to reduce the energy bill by making small adjustments throughout the day or week. You can address this to some extent on your own by setting a schedule using presets for things like sleep or Eco mode at desired times of day.

You do have plenty of remote control options, either from the Google Home app or through integrations with the Google Assistant or Amazon Alexa, so you can set up voice control if you like. This way you can say, “Hey Google, make it cooler” or “Alexa, set the living room thermostat to 71 degrees.”

If you prefer physical interaction, in place of the Learning Thermostat’s circular moveable bezel the $129 Nest Thermostat features a capacitive touch sensor on the top right side. Here you can slide your finger up or down to adjust temperature and tap it to trigger an action. And we’ll be honest, after a few days of use, we did get the hang of it, but it’s not as natural as the click wheel on the $249.99 Nest Learning Thermostat. It can ultimately take more interactions to get something done. When switching between cooling modes, you need to tap it once to pull a menu, scroll to the desired icon and tap again to select it. Throughout the day, though, you can swipe up or down to raise or lower the temperature.

The Nest Thermostat, oddly enough, doesn’t use the Nest app. This is part of a larger regrouping on Google’s part, but setup and control is done through the main Google Home app. It’s a pretty straightforward interface and you’ll be right at home if you’re already using this ecosystem for your smart home. Within the Home app, the interface for the Nest Thermostat mirrors the physical unit with the set temperature centered and the actual temperature (along with the humidity) directly below it.

Google offers the Nest Thermostat in four finishes — Snow, Charcoal, Sand and Fog. The circular unit features a rectangular display covered with a mirror finish, and while you may want to touch it, we wouldn’t recommend it. Installation is easy; like the Learning Thermostat, the Nest Thermostat can draw power from a C wire, two AA batteries or a power adapter.

Google has crafted a nice unit here that doesn’t shine as tech-savvy or feature a brilliant user interface. Still, the $129.99 Nest Thermostat succeeds as an affordable and intuitive unit that lets you easily control the temperature of your home.

Before installing any of the seven thermostats, we ensured we were going about the installation safely. This involved turning off the breaker to cut the power to our HVAC systems. From there, we removed the standard-issue nonsmart thermostat and began installing the thermostat being tested.

We followed the included instructions with each installation, and if the respective app featured an onboarding, we followed that as well. We took careful note of how intuitive the instructions were, and the app was helping to move us along with the process. After a successful install, we tested the available modes to ensure proper function. We lived with each thermostat for many days to get a feel for it and let it calibrate.

We tested control on the same Wi-Fi network with each app and while out of the house using cellular. If the thermostat featured geofencing capabilities, we tested that as well. On top of controlling through the companion app for each device, we also used the thermostats with all compatible smart home ecosystems.

Lastly, we examined the length and what was covered with the included warranties for each unit.

Ecobee 3 Lite ($169;

The Ecobee 3 Lite is the entry-level smart thermostat from the brand and sets out to complete what it aims to do. The larger touch screen was easy to use in our testing and mirrors the companion app for Android or iOS. It ultimately comes down to personal preference, but we missed having physical buttons to control the heating or cooling with.

Like the full Ecobee Smart Thermostat With Voice Control, this smart thermostat comes with a power adapter in the box, which is handy if your setup doesn’t feature a C wire for direct power to the unit. It’s an easy enough job to install it, but adds a bit to the install time. The Ecobee 3 Lite also supports a laundry list of smart home ecosystems: Amazon Alexa, Apple HomeKit, Google Home and SmartThings, among others.

Ecobee Smart Thermostat With Voice Control ($248.64;

The more expensive Ecobee goes beyond being just a smart thermostat. With a speaker and set of microphones on board, this truly is a smart speaker on your wall and has the ability to be used as an Amazon Alexa smart speaker for playing music and answering queries of all sorts.

It also has a nearly identical heating or cooling control experience to that of the Ecobee 3 Lite. You’ll control it all through the Ecobee app for Android or iOS, along with a sizable touch screen on the front of the unit. We prefer the overall installation process and controls to the Nest Thermostat.

Honeywell Home T5+ ($124, originally $150;

If you have other Ring devices, consider the Honeywell since it works out of the box with the Ring ecosystem. Otherwise, these are pretty standard thermostats. Like the Ecobees, these include a power adapter in the box. It has a bit more of a bulky look with a black square design, though it’s still fairly easy to control. We’ll also note that it did take a few tries to get the T5+ on our Wi-Fi network.

Honeywell Home T9 ($143.57, originally $199.99;

The Honeywell Home T9 is pretty expensive at $199.99 but doesn’t strike a chord with a design that meets that price level. You’ll need to deliver power through a C wire or through the included adapter, and after that, installation is pretty simple. The T9 also supports geofencing, which can have it opt for an eco temperature when you’re out and turn it back on as you approach your home. This smart thermostat also supports Amazon Alexa, Apple HomeKit and Google Home.

Wyze Thermostat ($78.98;

For $59.99, the Wyze Thermostat was the most affordable out of the bunch, and while it did work fairly well in our testing, the design was ultimately a bit lackluster. It features a knob design that is reminiscent of the Nest Learning Thermostat but wasn’t that smooth in operation. It also took a pretty forceful click to engage and set the temperature. The Wyze Thermostat also integrates with Amazon Alexa or the Google Assistant.

As a whole, the build wasn’t that great, and the setup took a bit longer, but for $70 more, we believe the investment for the base Nest Thermostat makes the most sense.

Read more from CNN Underscored’s hands-on testing: