FDA panel recommends J&J COVID booster for 18 and up Xbox Series X mini fridge US to lift travel restrictions for vaccinated international visitors NASA's Lucy mission: How to watch Apple Octoer event: How to watch PS5 Pro
CNET editors pick the products and services we write about. When you buy through our links, we may get a commission.

Best smart thermostat to buy in 2021

We tested a group of popular smart thermostats from Ecobee, Honeywell, Nest and more. Here's what you need to know.

smart thermostat is an app-enabled smart home device that does more than manage your home's cooling and heating system. You can adjust your thermostat remotely anywhere your phone or mobile device is connected to a Wi-Fi or cellular network, so you can stay in control whether you're at the grocery store, on vacation or just on the couch. Many models can also be voice controlled via SiriAlexa or Google Assistant.

Some smart thermostat systems also use smart features like a motion sensor or occupancy sensor that determines if you're home or away and automatically change the temperature -- both heating and cooling -- for you, without you having to fiddle with your HVAC system. Others have a geofencing feature: Once you get a certain distance from your home, they automatically switch to away mode and then back to home mode when you return. Then there are features like remote sensors, a power extender kit, thermostats that work with existing infrastructures (in other words, that are compatible with Apple HomeKit) and, of course, thermostats that measure your energy usage so that your home can be more energy efficient. Truly, a smart home thermostat is an energy-saving smart device that's good for both the environment and your wallet.

Even better, these options offer way more than a programmable thermostat -- you want a learning thermostat that gets better at regulating your home's temperature to suit your preferences.

To accompany these modern features, many connected heating and air conditioner systems boast innovative designs. From a rounded shape to a responsive touchscreen, smart thermostats look a lot different than your traditional thermostat and make it easy to set and maintain your desired temperature. They can also send you smart alerts, sync with the rest of your smart home devices and some even respond to voice commands.

Let's explore the available options model by model. We'll highlight what makes each model stand out from the rest and ultimately pick an overall winner of the best smart thermostat from the pack. Without further ado, here's a list of smart thermostats we've tested recently:

Amazon also recently unveiled the Amazon Smart Thermostat at its September 2021 invite-only launch event that included the Astro robot, the Echo Show 15 and many other Echo and Ring devices. The $60 smart thermostat device works with Alexa, according to Dave Limp, Amazon senior vice president for devices and services, and is meant to work with most existing HVAC systems. The product is available now for preorder and is scheduled to be released Nov. 4. We will review the device when we can and will update this list accordingly, so check back periodically for updates. 

Find out more: Amazon showed off a robot, a thermostat and more at its big 2021 event

Chris Monroe/CNET

The Ecobee Smart Thermostat is my favorite pick for best smart thermostat available today. Yes, it's expensive at $249, but it has the performance and features to back it up -- especially if you want to talk to Alexa without having to buy an Amazon Echo. If you don't want or need an Amazon Alexa speaker, the $169 Ecobee3 Lite Wi-Fi thermostat is also a great option.

Read our Ecobee SmartThermostat with Voice Control review.


Now playing: Watch this: Ecobee's new thermostat is part Alexa speaker
Chris Monroe/CNET

The Nest Thermostat is an Alexa- and Google-Assistant-enabled smart thermostat from Google -- and it's only $130, or sometimes even less. Compared to the high-end $250 smart thermostats, this model offers a great value. It also looks nice, is easy to install and use in the Google Home app (or with a voice command; compatible smart speakers and displays sold separately) and performs well.

If you're searching for a solid entry-level smart thermostat, the Nest Thermostat is an excellent option.

Read our Nest Thermostat review.


Chris Monroe/CNET

The Honeywell Home T9 is a $200 smart thermostat from Resideo. The T9 works with Alexa and Google Assistant and offers reliable performance and a solid app. The device also comes with remote humidity, proximity and temperature sensors, making it the smartest sensor accessory around. Nest's sensor only provides ambient temperature readings, while Ecobee's sensor only has temperature and proximity detection capabilities.

Read our Resideo Honeywell Home T9 Smart Thermostat review.


Tyler Lizenby/CNET

I hold that the $249 Nest Learning Thermostat is still the best-looking smart thermostat out there. Its rounded design harkens back to old-school thermostats, but the device has a modern look that fits in with nearly any home decor. The $169 Nest Thermostat E looks nice too, but it has more plastic components that aren't as appealing as the Learning Thermostat's stainless steel.

Read our Nest Learning Thermostat Third Generation review.


Testing a thermostat

Let's talk about testing. Smart thermostats start with the installation. Installations can vary widely from thermostat to thermostat and between HVAC systems, but there are some basic steps required for installing these devices. As always, consult a professional installer if you have any questions about the setup process. Here are the general steps:

  • Turn off power to your thermostat at the circuit breaker
  • Remove the old thermostat
  • Install the thermostat's base plate with the included screws
  • Attach the wires to the wire terminals 
  • Snap on the faceplate
  • Turn on power at the circuit breaker

Was the thermostat setup especially difficult to install? If so, why? Certain models require a C-wire, for example, which can complicate the installation if you don't have one. Not sure what a C-wire is? Start here

From there, I move on to the app. Every smart thermostat has one. I download the app and create an account if I don't already have one. Then I configure the thermostat following the steps in the app. This usually means connecting to the local Wi-Fi network, giving your thermostat a name like "Hallway" or "Bedroom" and then you can start using your thermostat.

How well does the app work? Is it easy to navigate to the thermostat settings you need? Is it simple to create a schedule or enable geofencing? This factors into the thermostat's usability score, along with how simple the thermostat hardware itself is to control manually. 

I also test smart home integration, especially voice-enabled systems you can access through voice assistants like Alexa, Google Assistant or Siri. Most connected thermostats have compatibility with at least one voice assistant and some, like the Ecobee3 Lite and Ecobee Smart Thermostat, work with all three. Do the voice commands flow naturally, like they would in an actual conversation? Did the thermostat actually adjust the temperature -- heating and cooling -- according to your commands? 

All of these things determine a smart thermostat's overall score and how likely I am to recommend it. 

The best of the best from home energy