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Smart thermostats do more than automate a fixed heating and cooling climate control schedule. These app-enabled smart home devices make it possible to adjust your thermostat from your smartphone whether you're on the couch, at the grocery store or on vacation -- anywhere your smartphone is connected to a cellular or a Wi-Fi network. Many of these devices also work with Alexa, Google Assistant and Siri now too, giving you yet another way to adjust your thermostat settings with remote access. 

Some smart thermostat systems also use smart features like a motion sensor to determine if you're home or away and automatically change the temperature -- both heating and cooling -- for you. Other systems rely on a geofencing radius -- once you get a certain distance from your home, they switch to away mode and then back to home mode when you return.  

To accompany these modern features, a lot of connected heating and cooling systems boast innovative designs. From a rounded shape to a responsive touch screen, today's thermostats look different than they used to.

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. Here's a list of smart thermostats we've tested recently:

Read more: Amazon Echo, Google Nest and all the best smart home gifts of 2019      

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The Ecobee SmartThermostat 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 Alexa speaker, the $169 Ecobee3 Lite Wi-Fi thermostat is also a great option. Read our Ecobee SmartThermostat with Voice Control review.

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The Honeywell Lyric T5 costs $150, making it our choice for the best smart thermostat pick for those on a budget. I know that isn't exactly affordable. But it's a solid price tag for a Wi-Fi thermostat. Many models, including the Nest Learning Thermostat and the Ecobee4, cost $249. This makes the T5 a great "budget" option that works with Alexa, Google Assistant and Siri (via Apple HomeKit).  Read our Honeywell Lyric T5 Wi-Fi Thermostat review.

Read more: The best smart home devices of 2019

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The Ecobee SmartThermostat has a built-in Alexa speaker. Ask the speaker for the temperature, current weather forecast, to tell you a joke -- and to adjust the air conditioning of your smart thermostat, all without needing a separate Alexa speaker. This Wi-Fi programmable thermostat also offers mobile app integration with Google Assistant and Siri, so if you have a Google-Assistant-enabled smart speaker or a HomePod, you can control it with Google Assistant and Siri commands.  Read our Ecobee SmartThermostat with Voice Control review.

Read more: 12 smart thermostats to make your home the right temperature 

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 it 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.

Read more: Nest Thermostat, Amazon Echo, Philips Hue: The best smart home tech of the decade

Chris Monroe/CNET

The Ecobee mobile app setup is straightforward and easy to install and navigate. That sounds simple enough, but so many apps make it tough to find the specific setting or feature you're looking for. Not so with Ecobee's smartphone app. And that's important because the mobile app is one of the main ways to interact with your Wi-Fi thermostat when you aren't standing directly in front of it (aside from using a voice command).  Read our Ecobee SmartThermostat with Voice Control review.

Testing a thermostat

Let's talk about testing. Smart thermostats start with the installation. Installations can vary widely from thermostat to thermostat and HVAC system to HVAC system, 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 baseplate 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 SmartThermostat, 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. 

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Originally published earlier this year.