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The best smart thermostats for 2021

Tired of waking up to cold mornings in the middle of winter or arriving home to sweltering summer heat? While conventional HVAC systems allow for basic climate controls of your residence, a smart thermostat truly ups the ante. Once wired and connected to Wi-Fi, the best smart thermostats can be customized to fit your lifestyle, from temperature to time of day. Using your preferred mobile device, you can adjust the temperature on the go, monitor energy efficiency, and enable vacation settings for when you’re out of town. Plus, there’s all the majesty of voice assistant controls from leading artificial intelligence (A.I.) companions like Alexa and Google Assistant.

In this roundup, we break down the very best smart thermostats that you can run out and grab today, featuring brands like Ecobee, Nest, and Honeywell.

At a glance

The best smart thermostat: Ecobee SmartThermostat

Ecobee Smart Thermostat

There are a lot of reasons to love the Ecobee SmartThermostat. For starters, the install process is pretty painless. Even if you don’t have a C-wire, Ecobee has you covered with a power extender kit included. Plus, the installation instructions are easy to follow, and the setup process is quick.

The SmartThermostat has a responsive touchscreen display with a clean interface. It also has voice control built-in via Alexa, like the previous Ecobee. However, with the SmartThermostat, Alexa can play podcasts, playlists, news, and music from services like Spotify (and it actually has good sound). You can even use your thermostat for features like Alexa Calling, Messaging, and Drop In. However, if you’re not into Alexa, the Ecobee is also compatible with other platforms like Apple HomeKit, Google Home, SmartThings, and IFTTT.

The Ecobee SmartThermostat also comes with a SmartSensor. If you have hot or cold spots in your home, the sensor can help even things out and make your home more comfortable.

Read our full Ecobee SmartThermostart review

The best budget smart thermostat: Google Nest Thermostat

Google Nest Thermostat (2020)

Available in Snow, Sand, Fog, and charcoal colors, the Google Nest Thermostat is Google’s latest mid-tier offering, standing just a step behind its premier Learning model (featured below). Capable of Alexa and Google Assistant controls, the redesigned thermostat features a mirrored display and side-mapped touch controls as opposed to the physical settings dial of the previous E model.

Using the Google Home app, you can adjust the temperature, create customized routines, monitor HVAC usage, and more. There’s even a routine function that can be paired with other smart devices. For instance, uttering a voice command such as “good morning” can draw your smart blinds, tune your Google Nest Hub to your favorite morning podcast, and set your Nest Thermostat to your ideal 10:00 a.m. temperature. All of these great features can be had for only $130, which in the world of smart thermostats isn’t half bad.

Read our full Google Nest Thermostat review

The best smart thermostat for Google Home: Nest Learning Thermostat (3rd generation)

We really like the Nest Learning Thermostat because of its learning capabilities. After you install the device and set the temperature you like, the thermostat does the rest. Nest takes note of how you move around your house throughout the week, adjusting the various temperature settings according to the time of day and your habits. With the third-generation model, a new set of sensors called Farsight makes this even more accurate.

Farsight detects when you enter a room or walk past it up to five meters away, a significant improvement over earlier models. Additionally, up to 10 additional sensors can monitor temperatures in other rooms, further optimizing your heating and cooling. You can monitor temperature from a much farther distance thanks to a 3.25-inch screen, a half-inch bigger than previous models.

Like any good friend, the device will offer suggestions designed to save you money. Its ability to adjust the temperature of your home a half hour before you arrive from work only furthers its intuitiveness.

The best Alexa-enabled thermostat: Ecobee4

Ecobee4 smart thermostat close

Ecobee 3 was one of our previous favorites for large homes, as it allows you to add up to 32 (no, that’s not a typo) sensors to monitor conditions in large spaces. The Ecobee 4 is essentially the same thermostat in functionality and design, but with an important addition: Amazon’s Alexa voice service. Sure, the newer Ecobee SmartThermostat has an edge over the Ecobee 4 in terms of its Alexa features, but this doesn’t mean the Ecobee 4 isn’t still a great option.

Where the Ecobee 4 still feels a step behind is in its learning capabilities, which is the reason why we’ll still give the edge to Nest. Yes, Alexa is a good feature, but you need to remember that the speaker itself is pretty small and on the back of the device, making it okay for voice queries but not an option to listen to music or anything like that.

We would recommend the Ecobee4 over the Nest to those who might not already have an Echo. Digital assistant technology is one of those things that you just don’t know how convenient it is until you’ve tried it. Putting it in a thermostat is a neat idea since it’s always located in a central spot in your home.

Read our full Ecobee 4 review

The best thermostat with HomeKit: Honeywell Lyric

Honeywell Lyric

In a nutshell, the Honeywell Lyric taps into your location and local weather forecasts via Wi-Fi. The circular device will then anticipate potential temperature changes and compensate for the weather while offering a host of shortcut settings for straightforward programming and operation.

The thermostat features three standard modes — one for when you’re sleeping, one for when you’re leaving your home, and another for when you’re arriving — all of which you can adjust using the mobile app for iOS and Android devices.

The Honeywell Lyric will adjust accordingly to save you the maximum amount of money, but if you prefer to work outside the box, you can set custom settings to fit your household. Honeywell makes three of the five thermostats that work with SmartThings, including the Lyric. Much like the new Nest, it works with Alexa, but it can also work with HomeKit, which is something we can’t say for Google’s Nest thermostat.

Read our full Honeywell Lyric review

The smart thermostat with the most features: Johnson Controls GLAS

Johnson Controls GLAS review
Terry Walsh/Digital Trends

Looking for a smart thermostat with the most features and flashiest tech? The Glas sets out to impress with a translucent OLED screen, incredible interface and app for control options, and a general design that looks about 100 years ahead of its time.

However, as we noted in our review, the Glas has a great design, but many of these features only reach skin deep. Its actual thermostat features are more on par with the rest of today’s smart thermostats. The Glas offers schedule programming, occupancy sensors to detect people and set automatic schedules if you want, and compatibility with Alexa, Cortana, and Google Assistant. This compatibility includes built-in software, so you can actually talk to these voice assistants on the thermostat like Ecobee allows, although the quality won’t be as good as a dedicated speaker.

One of the most unique (although not unheard of) features Johnson Controls GLAS brings is indoor air quality monitoring to check not only humidity but also VOCs and CO2. Combine this with outdoor air quality reports on allergens, sunlight, and air quality (which Glas also provides), and you’ll have a great idea just how healthy your air is.

Read our full Johnson Controls GLAS review

The best smart thermostat for window units: Cielo Breez Plus Smart AC Controller

Cielo Thermostat for Window ACs

Smart thermostats aren’t just for homes with central HVAC systems. Thanks to companies like Cielo Breez, those of us stuck with window air conditioners, ACs on wheels, and mini-splits now have smart options for keeping the house comfy in the summer. The Plus works its magic by way of four infrared sensors that are built into the thermostat. These sensors interact with the infrared signals produced by your portable AC and its remote control, effectively learning the infrared language of your AC brand. All you have to do is mount the Plus module in the room your air conditioner is located in, connect to Wi-Fi, and your smart controls are up and running.

Additional capabilities for Alexa and Google Home let you control your ACs with simple voice commands or with your Alexa and Google Home apps. You can even set temperature and humidity triggers that will automatically power your AC when things get too hot. The icing on the cake with this non-HVAC savant is that once you’ve registered your Cielo Breez Plus, you can use the thermostat off-line to control power, fan speed, and temperature. Your bandwidth will sure be happy.

Research and buying tips

Can I install a smart thermostat myself?

Yes. If you have a bit of basic DIY knowledge (enough where you can install a basic light fixture), you can install most smart thermostats, provided you have the correct wiring setup. Here’s how to test your thermostat.

Do I have to have special wiring to install a smart thermostat?

Yes and no. Most smart thermostats require a common wire (C-wire), which allows for continuous flow of 24VAC power to the thermostat. If you have an older home, you may not have a C-wire. Some thermostats don’t require a C-wire, others, like the Ecobee SmartThermostat, include an adapter for homes that don’t have a C-wire. You can also run a wire between your furnace and thermostat or purchase a separate adapter if needed.

Do I need room sensors?

It depends. Typical thermostats measure the home’s temperature in one area of the home, like a hallway or entryway, and use that measurement to heat or cool the entire home. Room sensors are more specific. They measure the temperature in a specific room, like a bedroom or basement, and adjust the temp based on that individual area. If you have a relatively large home or if you have some rooms that don’t heat or cool as well as others, room sensors can help heat or cool your home better. On the other hand, if you live in a smaller space or a wide-open area, room sensors probably aren’t necessary.

What is the best smart thermostat app?

This depends on how advanced you want your system to be. If you want a simple and clean app where you can schedule your heating and cooling and perform basic functions, the Honeywell Total Connect Comfort app is a good choice. However, if you’re looking for something with more features, you may prefer the Nest app.

What is the best smart thermostat on Amazon?

Amazon sells our pick for the best smart thermostat overall, the Ecobee SmartThermostat. Take a look at some of the best smart thermostat deals to save money this holiday season.

What is the best smart thermostat to save money?

A smart thermostat can save you between 10% to 25% on your heating and cooling costs. Ecobee claims its thermostats save up to 23%. Our testing found the Honeywell Color Thermostat reduced total energy consumption by 15%. How much you’ll save depends on a variety of factors, including how you use your smart thermostat, your heating and cooling preferences, climate, your HVAC system, insulation, the age of your home, and more.

How we test

Successful smart thermostats aren’t determined solely by how well they regulate temperature; their overall costs and speed at which they modify temperatures also play a part. When we conduct our testing, we monitor performance levels, how user-friendly the thermostat is, the installation process, and whether it saves you money. 

There’s a learning curve to figuring out exactly how your smart thermostat works, but once you figure it out, you’ll see how it can benefit you. We study how steep the learning curve is and how well the device can detect people coming in and out. Many customers also see the thermostat as the “center of command” for their smart home ecosystems. With that in mind, we test to be sure the thermostat communicates and connects well with other devices.

We made sure to use voice commands when testing thermostats because we wanted to make sure they were responsive, whether they were compatible with Apple HomeKit, Amazon Alexa, or Google Assistant. Generally, we also check to see whether the thermostat is energy efficient and saves your house money and how much you’ll need to interact with the device after it begins to learn your usual routines.

While we try to test every thermostat in the Digital Trends lab or an employee’s home, we’re not able to get to them all. In that case, we do extensive online research before we recommend a product.

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