The Best Smart Thermostats of 2021

Control the heating and cooling of your home the smart way—and save money—with a high-tech thermostat that suits your space, style, and budget. and its partners may earn a commission if you purchase a product through one of our links.

The Best Smart Thermostat Option


Smart thermostats, which connect with home automation systems, go beyond their programmable predecessors to offer a whole new level of residential temperature control with the added bonus of energy savings. Today’s models all combine climate control with connectivity, but features vary from unit to unit.

Some track and analyze your HVAC’s energy usage, monitor humidity, and notify you when it’s time to change the air filter. Others sense when you are at home and automatically adjust the temperature accordingly. Still, others can learn when you’re on your way home and tweak the temp so that your home feels comfortable upon your arrival.

The best smart thermostat for any home is one that offers ample control to heat or cool a home when needed. With the right unit, you could save 20 percent or more on your utility bills. Read on to understand the criteria used to designate the models below as some of the best smart thermostats and to help you make the right choice for your needs.

  1. BEST OVERALL: Google Nest Learning Thermostat
  2. BEST BUDGET: Emerson Sensi Wi-Fi Smart Thermostat for Smart Home
  3. BEST TOUCH SCREEN: Emerson Sensi Touch Wi-Fi Smart Thermostat
  4. BEST FOR MULTIPLE ROOMS: ecobee4 Smart Thermostat with Built-In Alexa
  5. BEST FOR AIR CONDITIONER: Sensibo Sky – Air Conditioner Controller
The Best Smart Thermostat Option


Before You Buy 

Smart thermostats offer energy savings and, once set up, they’re worry-free—no more getting out of bed at night because you forgot to turn the heat down or coming home to a cold house because you’re trying to save on utility costs. Yet while smart thermostats offer convenience and conserve energy, they’re not for everyone.

To function, the home must have an installed Wi-Fi network. For installation, you may wish to have the thermostat installed by a pro if you’re not tech-savvy. Before buying a smart thermostat, keep the following factors and features in mind so you can make an informed purchase.

What to Look for When Buying the Best Smart Thermostat

The best smart thermostat is one that fits the user’s budget, is compatible with their HVAC system and other smart home technology, and is easily programmable. If a thermostat is too complex to configure and operate, it won’t save any money. Consider which of the following is a “must have” or “don’t want” before selecting a unit.

Occupancy Sensing

This is a smart thermostat’s ability to detect when someone is in a room and automatically adjust the temperature to suit. The function is performed via remote sensors installed in different parts of the house. When a sensor detects movement, the smart thermostat adjusts the temperature to a comfortable level.

Remote sensors can be used with standard HVAC systems and also with zoned HVAC systems that permit the heating of selective rooms. The majority of smart thermostats feature occupancy sensing.


This GPS-based detection system saves on utility costs because it doesn’t start heating or cooling until you’re on your way home. Geofencing works via a downloaded app on your smartphone.

To use, simply program a radius around your house—of, say, three miles—and when your smartphone enters the radius, it signals your smart thermostat to heat or cool the house in preparation for your arrival.

Mobile Apps

All smart thermostats can be controlled from smartphones by the use of downloadable apps. Most smart thermostats have apps that work with both iOS and Android devices, but not all, so check before buying.

Smart Home Integration

Smart thermostats are designed to integrate with popular home automation systems such as Amazon Alexa, Wink, Vera, SmartThings, and Logitech Harmony. Some are compatible with only one or two systems, so ensure that the thermostat you buy will integrate with the system you’re using.

Power Needs

Smart thermostats require more electricity than either manual or programmable thermostats to power their network connections and GPS functions. This means the model you select may require a common wire (also known as a C-wire) that runs from the thermostat to the HVAC system.

If your home is less than 10 years old, it probably already has a C-wire. If not, you can have one installed, or you can purchase a smart thermostat that doesn’t require a C-wire to function. Some thermostats come with a power extender kit (PEK) as an alternative to a C-wire.

The Best Smart Thermostat Option


Tips for Buying and Using Smart Thermostats

Shopping for a smart-home thermostat can be confusing, and a tendency to buy before checking out all the pros and cons can result in a disappointing purchase. A thermostat is only as good as its useful features.

  • Stay within your budget. Smart thermostats range from around $125 up to $500. Don’t be tempted to pay more for features you likely won’t use.
  • Follow all setup instructions carefully. Some smart thermostats are programmed only by a smartphone, while others need time to “learn” the residents’ habits to regulate the home’s temperature.
  • Don’t turn off your smartphone’s location if the thermostat uses geofencing to turn the heat up and down. Leave the location on, and you won’t worry about coming home to a house that is either too hot or too cold.

Our Top Picks

To qualify as a top pick, a smart thermostat must be easy to use. It must connect with today’s most popular smart home automation systems, and it must be dependable. The following thermostats all require a home Wi-Fi system, and while each one is best suited for various purposes, any one of the following would be an asset in most homes.

Best Overall

The Best Smart Thermostat Options: Google Nest Learning Thermostat

One of the most popular smart thermostats available, the Google Nest thermostat integrates with Google Assistant and Amazon Alexa and syncs with other Nest devices for complete smart home integration.  When you perform repetitive tasks, such as turning down the heat at bedtime and turning it up the next morning, the thermostat learns and remembers your choices and begins changing its settings automatically for you.

The Google thermostat also features occupancy sensing and geofencing (sensors sold separately). This system stands out from the pack for its easy setup, high-resolution screen, and impressive ability to learn the patterns and preferences of household members. The device operates on either a rechargeable lithium-ion battery or by connection to a C-wire.


  • Compatible with Google Assistant, Alexa, and other Nest devices
  • Automatic temperature control
  • High-resolution screen
  • Multiple power source options


  • Occupancy sensing and geosensing sold separately

Best Budget

The Best Smart Thermostat Options: Emerson Sensi Wi-Fi Thermostat for Smart Home, ST55

This nicely priced and fully featured smart thermostat offers geofencing, seven-day scheduling, temperature and humidity alerts, and energy usage reports. Easy to install thanks to step-by-step video instructions, the Emerson can be powered by either a C-wire or a PEK, and it integrates with Google Assistant, Amazon Alexa, Wink, and Apple HomeKit (a C-wire is needed for Apple HomeKit).


  • Affordable unit
  • Compatible with Alexa, Wink, Apple HomeKit, and Google Assistant
  • Alerts for humidity and energy usage
  • 7-day scheduling


  • A C-wire is required for use with Apple HomeKit

Best Touch Screen

The Best Smart Thermostat Options: Emerson Sensi Touch Wi-Fi Smart Thermostat, ST75

In addition to both iOS and Android connectivity, the Emerson smart thermostat allows users to easily control all thermostat functions via a large high-definition touch screen panel. It requires a C-wire for operation (no other option) and integrates with many smart home systems, including Alexa, HomeKit, Google Assistant, and Wink.

This Emerson model features smart alerts, which detect temperature or humidity extremes and alert you via your smartphone. Other helpful features include energy usage reports, seven-day scheduling, and geofencing. Occupancy sensing is not available on this model, however.


  • Compatible with iOS, Android, Alexa, HomeKit, Google Assistant, and Wink
  • Smart alerts for humidity, energy usage, and temperature
  • 7-day scheduling and geofencing


  • Requires a C-wire for installation
  • No occupancy sensing

Best for Multiple Rooms

Best Smart Thermostat

For uniform climate control throughout the house, consider the ecobee4 smart thermostat, which includes a sensor to place in another room. The sensors (more offered separately) monitor the temperature in the rooms and adjust the overall heat and AC output for the entire house or for specific zones if the house features zoned climate control.

The ecobee4 senses occupancy and reduces HVAC output when the home is empty. The sensors should be placed in two of the most-used rooms, such as a family room and a kitchen, for the best results. The thermostat is compatible with Alexa, Google Assistant, Microsoft Cortana, Wink, and other popular home automation systems, and it syncs with both iOS and Android devices.


  • Compatible with iOS, Android, Alexa, Google Assistant, Cortana and Wink
  • Automatically reduces HVAC output
  • 2 climate control sensors
  • Built-in occupancy sensing


  • Additional sensors must be purchased separately

Honorable Mention

The Best Smart Thermostat Options: Sensibo Sky - Air Conditioner Controller

While most smart thermostats sync only with central HVAC systems, the Sensibo Sky air conditioner controller offers smart home syncing with individual AC units, including mini-split ACs, window ACs, and portable AC units. The only requirement is that the AC unit has an existing remote control. Like other smart thermostats, a Wi-Fi system is necessary for operating the Sensibo thermostat.

The thermostat syncs with both iOS and Android devices and can be used with Alexa, Google Home, and Apple Siri systems. The Sensibo smart thermostat does not require a C-wire, so installation is fast and DIY-friendly.


  • Compatible with Alexa, Google Home, and Apple Siri
  • Works with window, portable, and mini-split AC units
  • Easy installation; no C-wire required


  • AC units must have a remote control and WiFi connection

The Advantages of Owning the Best Smart Thermostat

Convenience and reduced utility bills top the list of reasons for installing smart thermostats, but they’re not the only reasons.

  • Users can turn the heat (or AC) up or down remotely.
  • The HVAC system can be configured to run less when no one’s home for added energy savings.
  • With some smart thermostats, energy use can be tracked and analyzed to help understand where loss occurs.

Our Verdict

Selected for its numerous intuitive features, the Google Nest has the ability to control temperature automatically, a high-resolution screen that’s easy to read, and flexible power source options. As an alternative to the top pick, the Emerson Sensi Wi-Fi comes at a lower price with more basic functionality, like scheduling humidity and temperature changes (as opposed to automatic adjustments).

How We Chose the Best Smart Thermostats

After evaluating the important factors to consider when investing in a smart thermostat, the top picks showcase some of the best features one can buy for controlling their home’s air quality, and humidity. Every recommendation represents a leading brand known to produce reliable smart technology for heating and cooling systems.

The majority of the thermostats above are compatible with multiple leading smart home systems including Alexa, Google Assistant, Nest, Wink, and Apple HomeKit. You can rely on many of these systems to provide automatic climate control, usage and humidity alerts, occupancy sensors, and geofencing. These systems were also selected for user-friendly design elements like large or high-resolution screens that enhance visibility.


Those who want more info on shopping for and using a smart thermostat for the first time may find answers to these common questions.

Q. Can I make my thermostat smart?

Theoretically, it may be possible. Manufacturers are producing modules and transceivers that can make certain types of existing thermostats compatible with smart home systems. This technology is still in its infancy, however, so you might be better off buying an actual smart thermostat for now.

Q. Is replacing a thermostat easy?

Replacing a standard thermostat with a smart thermostat may be beyond most DIYers’ scope because smart thermostats often require the addition of a C-wire that runs from the thermostat to the HVAC system. This wire carries electricity and should be installed by an electrician. However, a few models come with an alternate power adapter, and these are simpler to install.

Q. Can I replace my thermostat with any thermostat?

For the most part, yes. Today’s thermostats, whether they’re smart or not, are designed to work with most HVAC systems. However, if your existing system is more than 20 years old, some of the newer thermostats may not connect.

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