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Three black and two white smart thermostats sit on an orange background Credit: Reviewed / Google / Honeywell / Amazon / Ecobee / Sensi

The Best Smart Thermostats of 2024

Recommendations are independently chosen by Reviewed's editors. Purchases made through the links below may earn us and our publishing partners a commission.

Three black and two white smart thermostats sit on an orange background Credit: Reviewed / Google / Honeywell / Amazon / Ecobee / Sensi

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Reviewed's mission is to help you buy the best stuff and get the most out of what you already own. Our team of product experts thoroughly vet every product we recommend to help you cut through the clutter and find what you need.

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Editor's Choice Product image of Nest Learning Thermostat, 3rd Gen
Best Overall

Nest Learning Thermostat, 3rd Gen

Check Price at Amazon

The Nest Learning Thermostat is easy to install, simple to control from anywhere, and works with Amazon Alexa and Google Assistant. Read More

Pros

  • Works with Alexa and Google Assistant
  • Intuitive
  • Support temperature sensors

Cons

  • Does not support Apple HomeKit
2
Editor's Choice Product image of Sensi Touch 2 (2023)
Best Traditional-Style

Sensi Touch 2 (2023)

Check Price at Amazon

An intuitive touchscreen, great temperature accuracy, and remote sensing make this a solid smart thermostat pick. Read More

Pros

  • Intuitive touchscreen
  • Excellent temperature control
  • Remote temperature sensing

Cons

  • Basic styling
3
Editor's Choice Product image of Google Nest Thermostat
Best Value

Google Nest Thermostat

Check Price at Amazon

The Nest Thermostat offers several of the same features as the more robust Nest Learning Thermostat but at a fraction of the cost. Read More

Pros

  • Compatible with Amazon Alexa and Google Assistant
  • Google Home app is easy to use
  • Works well

Cons

  • No native integration with Apple HomeKit
  • Trim kit is additional cost
  • Doesn't work with Nest Temperature Sensors
4
Editor's Choice Product image of Ecobee Smart Thermostat Premium (2022)
Best for Smart Home

Ecobee Smart Thermostat Premium (2022)

Check Price at Amazon

Lavishly smart, the Ecobee Smart Thermostat Premium can control a wider than average amount of HVAC systems and smart home features. Read More

Pros

  • Great smart features
  • Multiple HVAC system control
  • Useful zone scheduling

Cons

  • Pricey
  • Requires specific wiring
5
Product image of Ecobee Smart Thermostat Enhanced (2022)
Best with Motion Sensor

Ecobee Smart Thermostat Enhanced (2022)

Check Price at Amazon

This smart thermostat connects to Wi-Fi and heeds to voice commands if paired with a smart hub. It also has high temperature sensing accuracy. Read More

Pros

  • Excellent temperature regulation
  • Radar sensor detects when you are home
  • Wide smart home compatibility

Cons

  • Can not be installed in a heat-only 2-wire system
  • Best Overall Nest Learning Thermostat
  • Best Traditional-Style Sensi Touch 2 (2023)
  • Best Value Google Nest Thermostat
  • Best for Smart Home Ecobee Smart Thermostat Premium
  • Best with Motion Sensor Ecobee Smart Thermostat Enhanced (2022)
  • Other Smart Thermostats We Tested
  • How We Tested Smart Thermostats
  • What You Should Know About Buying Smart Thermostats
  • What is a C-wire?
  • Privacy
  • More Articles You Might Enjoy

There are plenty of options when it comes to great smart home devices, but few have the potential to impact your overall comfort more than a programmable thermostat.

If you want to remotely control the temperature in your home, save energy and money on utility bills with more efficient heating/cooling, or just want to engage in the longstanding thermostat war with your significant other from anywhere in the world, a programmable Wi-Fi thermostat is for you.

With so many options available, it’s hard to know where to start. That’s why our smart home experts have done extensive testing to find the best smart thermostats on the market right now.

We can confidently say that the Nest Learning Thermostat (available at Amazon) is the best of them all, with an easy setup, intuitive controls, and voice commands. Looking for something cheaper? The regular Nest Thermostat (available at Amazon) offers great value.

Credit: Reviewed / Leigh Harrington

The Nest Learning Thermostat can be controlled by dial or by smart app, and it is our best overall smart thermostat.

Best Overall
Nest Learning Thermostat
  • Smart home compatibility: Google Assistant, Amazon Alexa, Nest, Insteon, Nexia
  • C-wire required: No
  • Dimensions 3.3 in diameter, 1.21 in deep

Google's Nest Learning Thermostat is one of the biggest names in the home heating space, partially because it was one of the first well-designed connected thermostats on the market. Even a decade after its introduction, it's still the best smart thermostat for most people, thanks to its sleek, intuitive design and robust set of smart features.

If you've ever used an iPod, the Nest Thermostat will be familiar to you—in fact, it was designed by Tony Fadell, the designer of the original iPod hardware.

Once it’s hooked up to your Wi-Fi network, changing the temperature is as simple as rotating the thermostat's dial. You can use the app to set a traditional time-of-day schedule more easily than most non-smart thermostats. You can also simply let the Nest learn your daily habits and adjust to a comfortable temperature automatically.

This feature is great for those who don't want to put in any effort, but might be a bit too confusing for people who like to fine-tune their schedules, so you can turn it off if you wish.

Like many other smart thermostats, the Nest can use its built-in sensors and your phone’s location to determine when you aren’t home, and automatically adjust your home temperature to save you money and energy. It's also compatible with the energy-saving plans and rebates offered by many utility companies. You can adjust it with your voice using Alexa or Google Assistant and even get reminders when it's time to change your HVAC filter.

Nest offers sensors you can put in different rooms to adjust the temperature based on where you are at any given time. Sensor functionality is limited compared to competitors like Ecobee and Honeywell. Still, overall the Nest’s ease of use more than makes up for that slight shortcoming.

Our only other gripe with the Nest—besides its heftier price tag (which, again, rebates can help with)—is its setup. The actual process is quite easy, and the Nest app will walk you through it step-by-step if you've never installed a thermostat before. But in an effort to stay simple and compatible with a wide variety of heating and cool systems, the Nest uses a workaround to draw power in homes without a common wire (or C-wire).

The thermostat will function normally in most cases, but can cause problems with certain HVAC systems. If your home doesn't have a C-wire, we recommend having an HVAC professional install one, or using a thermostat like the Ecobee Smart Thermostat, which uses a slightly more complex (but reliable) conversion kit to power itself.

Read our full review of the Nest Learning Thermostat (third-gen)

Pros

  • Works with Alexa and Google Assistant

  • Intuitive

  • Support temperature sensors

Cons

  • Does not support Apple HomeKit

Buy now at Amazon

$249.99 from Best Buy

$249.00 from Target

$249.00 from Home Depot
Credit: Reviewed / Dave Ellerby

The Sensi Touch 2 smart thermostat looks and operates much like a traditional programmable thermostat, but it offers excellent smart features.

Best Traditional-Style
Sensi Touch 2 (2023)
  • Smart home compatibility: Amazon Alexa, Google Assistant, Samsung SmartThings
  • C-wire required: Yes
  • Dimensions: 3.25 X 5.6 X 0.77 inches

Sensi isn't a household name in the smart thermostat space (even among tech nerds like us), but it occupies a good niche: The Sensi Touch 2 Smart Thermostat is similar to a traditional thermostat in terms of ease of use.

The Sensi Touch 2 is the most high-end Sensi model. Installation requires a C-wire, and the app walks users through a simple set-up. The terminal blocks have push connectors, similar to those used by Nest and Ecobee, making connecting wires faster and easier.

The unit uses an intuitive touchscreen control. The styling isn’t as sleek and compact as some other smart thermostat options, but the larger screen may make the controls more accessible for some users. The menu system is easy to navigate when adjusting temperature settings.

On average, the unit sensor was a little over a degree off compared to our NIST-calibrated thermometer. This isn’t a big deal, as not many users would notice that level of discrepancy.

The Sensi Touch 2 can be integrated with extra room sensors, available for purchase separately. These sensors monitor temperature and humidity at an independent location away from the base unit. They can be wall-mounted using the screw and drywall plug provided, or used freestanding with the included plastic stand.

Remote sensing gives a better sense of average conditions, especially in a larger home. You can connect up to 15 extra sensors to the base unit. With temperature averaging across the sensors, the system accuracy improved to within 1 degree of the measured temperature.

The thermostat also has a dehumidification mode. It doesn’t do this via a dehumidifier (unless there’s one integrated into your HVAC system), it uses an approach called overcooling. If you activate this mode via the app, the thermostat will run up to 3 degrees cooler than the set point. Cooler air holds less moisture, so cooling will make space feel less humid as the absolute humidity will drop slightly.

The Sensi Touch 2 Smart Thermostat is a replacement for the Sensi Touch Wi-Fi Thermostat, which we previously tested back in 2017. This older version is still available for purchase (for now). But, thanks to its better touchscreen interface and extra room sensor pairing (not an option for the older Touch) we think this is the one worth buying.

Read our full review of the Sensi Touch 2 Smart Thermostat

Pros

  • Intuitive touchscreen

  • Excellent temperature control

  • Remote temperature sensing

Cons

  • Basic styling

$184.95 from Amazon

$221.08 from Walmart
Credit: Reviewed / Rachel Murphy

The Nest Thermostat's display shows information about the date, time, and weather. It also shows the current temperature inside of your home, as well as humidity levels.

Best Value
Google Nest Thermostat
  • Smart home compatibility: Amazon Alexa, Google Assistant
  • C-wire required: Not required for most users (Note: We couldn’t get it to work properly without a C-wire.)
  • Dimensions: 3.3 inches diameter, 1.07 inches deep

The Nest Thermostat is a more basic version of our top pick, the Nest Learning Thermostat, scoring only slightly lower. Unlike the Nest Learning Thermostat, it does not work with the Nest app and cannot learn your temperature preferences over time.

However, the new Nest Thermostat offers comparable features to the Nest Learning Thermostat like Eco Mode, Home/Away Assist, and scheduling features to help you save on energy costs. All in all, it’s a good value for the money. We found these settings easy to adjust within the Google Home app and enjoyed reviewing the energy reports, which offer helpful insights into when your unit is running and for how long.

The first HVAC system we tried didn’t have a C-wire, and we experienced unpredictable behavior that Nest attributed to the lack of a C-wire.

With the second system, we had a few hiccups during the setup process. However, Nest customer service sent us a new thermostat right away. Once the replacement was connected, the thermostat performed well at heating and cooling. Everything you need to get started is in the box except the trim kit, which can be purchased separately.

Read our full review of the Nest Thermostat

Pros

  • Compatible with Amazon Alexa and Google Assistant

  • Google Home app is easy to use

  • Works well

Cons

  • No native integration with Apple HomeKit

  • Trim kit is additional cost

  • Doesn't work with Nest Temperature Sensors

$119.59 from Amazon

$129.99 from Best Buy

$84.99 from Walmart
An Ecobee smart thermostat appears set up for testing at the reviewer's home.
Credit: Reviewed / Dave Ellerby

This smart thermostat is equipped to control lots of systems in your home, beyond the HVAC basics.

Best for Smart Home
Ecobee Smart Thermostat Premium
  • Smart home compatibility: Amazon Alexa, Apple Homekit, Samsung SmartThings, Google Assistant, IFTTT
  • C-wire required: Yes, may be able to get around with power extender
  • Dimensions: 4.09 x 4.09 x 1.02 inches

While the Nest aims to be easy and hassle-free, the Ecobee Smart Thermostat Premium is more about creating an incredibly feature-rich system. This is a smart thermostat that can do far more than just turn on the heating. It can even provide air quality monitors and use motion detectors to double as a home security system.

Its highly responsive touchscreen feels just right and gives you control of a plethora of settings. With a C-wire connection built in, this thermostat is designed for modern homes that have AC, heating, and a fan system wired in. It can even control other devices, like a humidifier.

Ecobee's scheduling may seem confusing at first blush, but it's nice once you get the hang of it. Instead of merely setting temperatures based on time of day, you set your desired "comfort zones" for different instances: Like setting the AC to 76 when you're at home, 80 when away, 74 when sleeping, and so on. Then you schedule those comfort settings for certain times of day, or assign them to Ecobee's external room sensors, one of which comes with the Premium model.

For example: You could set the Ecobee to switch to "sleep" temperature when your toddler is napping in the afternoon, and it will use the sensor in the toddler’s room to determine the temperature, rather than the thermostat's sensor in the living room.

Options like this make the Ecobee extremely powerful, alongside its geofencing features and other eco-monitoring options. Beyond its internal features, it’s also highly compatible with smart home ecosystems.

It includes Alexa and Siri voice controls built right in, and provides additional compatibility with Apple Home Kit, Samsung SmartThings, Google Assistant, and IFTTT. If you’re looking for a smart thermostat that can act as a hub for your whole home’s smart ecosystem, then this is the one.

Read our full review of the Ecobee Premium

Pros

  • Great smart features

  • Multiple HVAC system control

  • Useful zone scheduling

Cons

  • Pricey

  • Requires specific wiring

$219.99 from Amazon

$219.99 from Best Buy

$249.99 from Home Depot

$249.00 from Abt
A white smart thermostat reads 46 degrees and sunny weather
Credit: Reviewed / David Ellerby

The Ecobee Enhanced is a new mid-level thermostat from Ecobee, featuring a temperature sensor, plus humidity and motion sensors, voice control, and more.

Best with Motion Sensor
Ecobee Smart Thermostat Enhanced (2022)
  • Smart home compatibility: Amazon Alexa, Apple Homekit, Samsung SmartThings, Google Assistant, IFTTT
  • C-wire required: Yes, may be able to get around with power extender
  • Dimensions: 4.09 x 4.09 x .94 inches

The Ecobee Enhanced is a new mid-level thermostat from Ecobee, a slight step below the Ecobee Premium. The Enhanced has most of the same features as the Premium, minus air quality sensing and built-in Alexa/Siri. It also does not include an external room sensor like the Premium does.

If you own an older home with a basic, heat-only, 2-wire system, you will not be able to install the Ecobee without installing a C-wire first. However, the Ecobee Enhanced smart thermostat is a dual Wi-Fi device and will work on both 2.4 and 5 GHz networks. This means that you shouldn't have to worry about your type of home Wi-Fi when setting it up.

The touch interface on the thermostat is simple and intuitive. We used a thermometer with an NIST certificate of calibration to double-check the accuracy of the thermostat temperature setting and found that it was highly accurate. Switching between heating and cooling modes or adjusting preferred temperatures is easy.

The basic thermostat has a temperature sensor, plus humidity and motion sensors. If you don't have added sensors, the thermostat is only monitoring conditions at the hard installation point. Extra sensing is potentially important in a larger home, but it’s not a big deal if you're in a smaller, open-plan space.

Read our full review of the Ecobee Enhanced

Pros

  • Excellent temperature regulation

  • Radar sensor detects when you are home

  • Wide smart home compatibility

Cons

  • Can not be installed in a heat-only 2-wire system

$189.99 from Amazon

$189.99 from Best Buy

$189.99 from Home Depot

$155.00 from Walmart

Other Smart Thermostats We Tested

Product image of Sensi Wi-Fi Programmable Thermostat
Sensi Wi-Fi Thermostat
  • Smart home compatibility: Amazon Alexa, Google Home, Apple HomeKit, Samsung SmartThings, Vera
  • C-wire required: No, but with limited functionality
  • Dimensions: 3.75 x 5.88 x 1 inches

Sensi's standard Wi-Fi thermostat looks like a traditional thermostat (which may be a pro or a con depending on your preferences), but its wiring is more old-school as well, requiring a screwdriver for each contact.

It also allows for batteries to power the thermostat interface, and with some HVAC configurations, you might be able to use this in place of a C-wire, but we'd recommend contacting a professional before doing so.

While the interface uses actual buttons instead of a touchscreen, the usability is nearly identical to the Sensi Touch, minus the temperature and humidity notification features. In the Sensi Wi-Fi thermostat, the only HVAC settings are heat, cool, and off. This may be enough to dissuade some users from buying it, since auto is such a useful feature in those in-between seasons like spring and fall.

This model also includes the flexible scheduling and geofencing found in the Sensi Touch. We were able to successfully change the temperature with Alexa, Google Assistant, and Siri. Remote access with mobile data worked beautifully as well, though we did experience connection issues when we tested this thermostat last year, where the device showed as unavailable from the smartphone app despite the internet working.

Pros

  • Works with Apple HomeKit, Alexa, and Google

  • Straightforward set up process

  • Easy to control remotely

Cons

  • Some connectivity issues

$119.37 from Amazon

$122.99 from Best Buy

$94.95 from Walmart
Product image of Sensi Lite (2023)
Sensi Lite (2023)
  • Smart home compatibility: Amazon Alexa, Google Assistant, and Samsung SmartThings
  • C-wire required: No, but with limited functionality
  • Dimensions: 3.13 x 5.07 x .88 inches

The Sensi Lite thermostat is Sensi’s entry level model, and has real retro charm. As far as set-up goes, veteran homeowners will feel comfortable. The baseplate is exactly like an old-school thermostat. The wiring blocks even have screw connectors rather than the newer push-in connectors.

The Sensi Lite claims that no C-wire is required, and that’s true to an extent, but no more so than for other smart thermostats. Your level of control is limited without either a built-in C-wire or a system that adds C-wire function. Without access to the full range of smart functions, the Sensi Lite isn’t really special in its ability to function without one.

Accessing the basic thermostat settings is intuitive. There’s a familiar cogwheel icon in the top corner of the app display that lets you choose temperature units and set upper and lower temperature limits. The Sensi Lite has touch controls, but not a true touchscreen like the Sensi Touch 2.

Our test board showed that the thermostat responded quickly and accurately to changes in the settings, switching to heating, cooling, or fan circulation as required. Like its big brother, the Sensi Touch 2, the Sensi Lite’s temperature sensing is a little over one degree off compared to our NIST-calibrated thermometer. Most homeowners will not notice this discrepancy.

The control interface is pretty straightforward. The main control button lets you cycle through settings (heat, cool, off) and adjust the temperature set point via the arrows. However, we found the app interface much easier to use than the controls on the unit. The mode selections are more readily available on the app interface. The app also allows you to set a schedule, which doesn’t seem to be possible on the unit itself.

Pros

  • Compatible with Amazon Alexa, Google Assistant, and Samsung SmartThings

  • Option to prevent rapid AC system switching

  • Intuitive interface

Cons

  • You can't program a schedule on the unit itself

  • No push-in connectors

  • Needs batteries to operate

$87.99 from Amazon

$89.99 from Best Buy

$79.99 from Walmart
Product image of Amazon Smart Thermostat
Amazon Smart Thermostat
  • Smart home compatibility: Amazon Alexa
  • C-wire required: Yes, available with C-wire adapter
  • Dimensions: 3.56 x 3.56 x .84 inches

The Amazon Smart Thermostat is a simple, smart, and stylish smart thermostat that fits in flawlessly with the Amazon Echo ecosystem. It’s our pick for the best smart thermostat for Alexa. The device offers location-based learning features (Alexa Hunches) that can help you save on your monthly energy bill—a feature usually reserved for more expensive smart thermostats.

The thermostat works well with Alexa voice control, as you might imagine, and is easy to manage in the Alexa app, where you can also view detailed insights about the device’s energy usage. With Hunches, Alexa can learn your habits and temperature preferences, automatically making adjustments to your HVAC system when you're at home and away. You can automate your thermostat by scheduling temperature changes up to four times a day, seven days a week in the app.

The thermostat looks more expensive than it is. We like the minimalist design with rounded edges that lends itself to any style of home. We also found it straightforward to navigate and use. We especially like the large digital numbers that make it easy to see the temperature from across the room or in the dark.

As for downsides, it doesn't work with Google Home or Apple HomeKit smart home systems, and there are no remote temperature sensors, which can be helpful for regulating the climate for larger houses. You'll also need a C-wire in order to use the thermostat. If you don't have one, Amazon sells a version of the thermostat with a C-wire adapter that's still a bargain.

Bottom line: If you need a value-packed smart thermostat that works beautifully with Alexa and the Amazon Echo ecosystem, you’ve got to go with the Amazon Smart Thermostat.

Read our full review of the Amazon Smart Thermostat

Pros

  • Intuitive features

  • Works flawlessly with Alexa

  • Sleek design

Cons

  • No support for Google Home and Apple HomeKit

  • No remote temperature sensors

$79.99 from Amazon

$63.99 from Best Buy

$63.99 from Target

$69.78 from Home Depot
Product image of Ecobee Ecobee3 Lite
Ecobee3 Lite Smart Thermostat
  • Smart home compatibility: Google Assistant, Amazon Alexa, iOS, Android, Vera
  • C-wire required: Yes, alternatively you can use a power extender
  • Dimensions: 4.05 x 4.05 x 1 inches

Ecobee's lower-cost "Lite" thermostat is very similar to its more expensive sibling: It has the same touchscreen and app, and most of the same features. It's a bit slimmer, so it looks better against your wall. Unfortunately, it doesn't include the built-in Amazon Alexa microphones, nor does it come bundled with a room sensor. It does still come with the power extender to accommodate those without a C-wire.

Whether it's worth the discount depends on your usage. Since it doesn't come with a room sensor—which is part of what makes Ecobee's thermostats great—you'll probably have to buy a 2-pack separately, which will bring you up to the same cost as the Ecobee SmartThermostat (though you'll have two sensors instead of one). If you don't plan on using the Amazon Alexa mics and prefer the slimmer profile, the Ecobee3 Lite is a great alternative.

Pros

  • Works with Apple HomeKit, Alexa, and Google

  • Simple setup process

Cons

  • No built-in Amazon Alexa

  • No extra temperature sensor

Buy now at Ecobee

$149.00 from Amazon

$149.99 from Best Buy

$149.00 from Home Depot
Product image of Honeywell Lyric T5 Wi-Fi Thermostat
Honeywell Lyric T5 Thermostat
  • Smart home compatibility: Amazon Alexa, Google Assistant, Apple Homekit, IFTTT
  • C-wire required: Yes, or an adapter
  • Dimensions: 4.06 x 4.06 x 1.25 inches

Honeywell has been in the heating and cooling system business for over 100 years, but their smart thermostats haven't quite gained the recognition that other companies have.

The Honeywell Lyric T5 thermostat is the more basic cousin of the Honeywell Lyric Round thermostat. The full touchscreen on the T5 makes it easy to change the temperature and check the settings. The Lyric T5 lacks the motion sensor of the Lyric Round thermostat, but other than that, the experience with changing the temperature, geofencing, scheduling, and vocal assistant integration is identical.

The Lyric T5 looks a bit more industrial than the Lyric Round; its square black profile has a slightly smaller footprint than most standard thermostats. A new version of this thermostat is now available, but we haven't tested it. The new model, the Honeywell Home T5+, is available on Amazon.

Pros

  • Works with Apple HomeKit, Alexa, and Google

  • Easy to use

Cons

  • Connectivity issues

  • Requires a 2.4 GHz connection

Buy now at Amazon

$137.15 from Walmart

How We Tested Smart Thermostats

The Testers

We’ve had a variety of our smart home experts test smart thermostats for this guide, including Whitson Gordon, a freelance tech writer and former editor-in-chief of Lifehacker and How-To Geek, as well as Rachel Murphy, Reviewed's Home editor, and Dave Ellerby, Reviewed’s chief scientist.

The Tests

A rig for testing smart thermostats
Credit: Reviewed / Rachel Murphy

Here's a look at the rig we used for testing smart thermostats. When cool air comes on, the blue button lights up. When the heat is on, the red button lights up.

We test smart thermostats in a real home using a standard HVAC system, which includes a C-wire. We also test some of the thermostats using a powered stand-alone circuit with a five-wire setup common in many HVAC systems. This replicates outputs for cooling, heating and fan control circuits, indicating when they became active.

Our test circuit allows us to test how easy it is to set up the system, as well as the sensor accuracy. We can also tell whether the thermostat responds to temperature changes with appropriate heating and cooling outputs. We have noted each unit’s compatibility with non-C-wire-equipped systems where applicable.

For each thermostat, we safely switch off the HVAC circuit breaker, install the backplate, mount the front of the thermostat, and configure it with the smartphone app on both an iPhone and Android phone.

Once we successfully install and program the thermostat, we let it run while we test out the app, the thermostat's responsiveness, and any voice assistant functionality. Using Alexa, Google Assistant, and Siri, we put these programmable thermostats through their paces.

We also try out the extra features on each thermostat to make sure that they are actually useful. This primarily includes scheduling and geofencing, but can also include other features like room sensors.

What You Should Know About Buying Smart Thermostats

A standard green electrical panel stands open with all a home's circuits inside
Credit: Reviewed / Julia MacDougall

We became intimately familiar with the circuit breakers while testing smart thermostats.

If you're shopping for a smart programmable thermostat, be sure to answer these questions before you buy anything:

  • What kind of cooling and heating system do you have? Make sure you know your system before you buy a thermostat designed for central air.

  • Will your current HVAC setup work with a smart thermostat? (You may want to consult a professional before continuing.)

  • Do you have a C-wire? Most smart thermostats require a C-wire. Some thermostats will work without it or may require a separate conversion kit or adapter.

  • How much smart functionality do you want? Do you need geofencing (location-based) or "learning" features, or do you just need basic remote access from your phone?

  • Do you use smart assistants like Amazon Alexa, Siri, or Google Assistant? Are they compatible with the smart thermostat you're investigating?

  • Will you want to install the smart thermostat yourself, or will you want a contractor to do it? Keep in mind that contractors may favor smart thermostats not available for resale.

  • Finally—and perhaps most importantly—who will use this thermostat, and what is their level of tech-savviness? Just because you're comfortable using complex smart devices doesn't mean your spouse, roommate, or kids are, which may impact the thermostat you choose to buy.

What is a C-wire?

The image shows the thermostat wiring behind a Sensi Touch 2, including a C-wire.
Credit: Reviewed / Dave Ellerby

Don’t forget the C-wire: most smart thermostats need a constant power supply.

A C-wire, or common wire, is a steady power source. It keeps your thermostat’s screen bright and ensures a steady connection to Wi-Fi and Bluetooth.

This Wi-Fi connection gives you control of heating and cooling systems from your smartphone. It also enables more advanced features like geofencing, or voice assistants that let you turn the heat on by chatting to your smart speaker while you dice scallions in the kitchen.

Do I need a C-wire?

If your brand new home still smells of fresh paint and sawdust, then you might already have a thermostat C-wire installed.

Many older homes only have four wires: W-wire (heating), Y-wire (air conditioning), G-wire (fan), and any of a slew of other HVAC possibilities, including an R-wire for power to your heating and cooling system. (Even older homes are often rigged with only two wires, one for heating and one for cooling.)

The C-wire usually appears as a fifth wire. However, depending on your home’s HVAC, and whether you have systems like heat pumps or dual stage heaters installed, you could have more than five wires.

Some Wi-Fi thermostats come with systems that can power the thermostat using four wires. Often, these will pull power from a fan wire or another system.

However, this option can have downsides. Certain HVAC systems, such as the compressors on air conditioners, can be degraded when repeatedly turned on and off. As a rule, smart thermostats run best with a proper C-wire.

Most smart thermostat C-wires will be blue, though they can also be brown, purple, or black.

It’s important to remember that you can’t connect just any wire over to your C-wire connection as a power source. If you’re setting up an HVAC system for the first time, be very careful when identifying and connecting your home’s wire types.

Smart thermostat installation can be complex. If you find yourself in doubt, remember that it’s likely a good idea to stop and bring in an HVAC professional. Mistakes with wiring can be damaging and costly.

Privacy

Any Wi-Fi connected devices at home present an element of privacy risk. While smart thermostats don’t typically record audio or video of homeowners, the geofencing features may store location data the same way that your phone does. The good news is that there are steps you can take to help protect your smart home, if you’re worried about privacy.

As with any device, look for two-factor authentication. This safety feature sends a code to your mobile device before letting you log in. That way, if someone tries to hack into your account, you’ll get the code instead of them. You get a heads-up to change your password, and they get nothing but frustration.

You can also set up email or push notifications to let you know when somebody logs in to your system.

Finally, make a strong password with multiple letters, numbers, and characters for every one of your different accounts. With data breaches being such a routine part of everyday life, having different passwords is important.

If you use one password for your banking, email, and all your devices, having that password exposed in a breach can be disastrous. Using different passwords protects you.

Finally, when using smart assistants like Alexa, Google Assistant, and Siri, consider regularly deleting your voice recordings and muting the speaker’s mic when it’s not in use.

Looking for more privacy tips? Read our guide to securing your smart home.

Meet the testers

Rachel Murphy

Rachel Murphy

Editor, Home

@rachel_murphy

Rachel Murphy is Reviewed's home editor. She holds a journalism degree from the University of Central Florida. Prior to joining the team, she worked as a freelance writer for publications like Insider and Mashable, and as an associate editorial producer for Good Morning America. Aside from smart home tech, her interests include food, travel, parenting, and home renovation. You can usually find her sipping on coffee at any time of the day.

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Whitson Gordon

Whitson Gordon

Freelance Writer

Whitson Gordon is a valued contributor to the Reviewed.com family of sites.

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Dr. Dave Ellerby

Dr. Dave Ellerby

Chief Scientist

Dave Ellerby has a Ph.D. from the University of Leeds and a B.Sc. from the University of Manchester. He has 25+ years of experience designing tests and analyzing data.

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Checking our work.

Our team is here for one purpose: to help you buy the best stuff and love what you own. Our writers, editors, and lab technicians obsess over the products we cover to make sure you're confident and satisfied. Have a different opinion about something we recommend? Email us and we'll compare notes.

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