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What to Look for in a Smart Thermostat

An ecobee smart thermostat displaying weather
Josh Hendrickson / Review Geek
The number one thing to check before buying a smart thermostat is its compatibility with your HVAC system. Past that, you’ll also want to consider your budget, how easy it is to install and use, whether it’s compatible with your smart home ecosystem, and which features you want.

Smart thermostats add convenience to your busy life and help save you energy and money throughout the year. If you’re here, you probably already know that, and you’re sold on the idea of a smart thermostat. The next step is picking the right smart thermostat for you, which may be a lengthy process, but it’s an investment worth your time.

There are some smart thermostats that you’ve probably heard of, like the Google Nest thermostat or one of ecobee’s many thermostat options. But just because a smart thermostat is popular, it might not be the perfect option for you.

There’s a lot to consider when shopping around for a smart thermostat, from your budget to your smart home ecosystem preference to the features you want to see in a thermostat. With this guide, you’ll learn all the right questions to ask and end up with the smart thermostat of your dreams.


Investing in a smart thermostat can cost anywhere from $75 to $300, though most fall in the range of $100 to $200. But the flat price of a thermostat isn’t the only cost you should consider. Smart thermostats are often paired with sensors that you put in individual rooms or your doors and windows, each ranging from about $30 to $50. Some companies, like ecobee, may also offer a monthly security subscription to pair with motion sensors and your thermostat.

Compatibility With Your HVAC System

An ecobee mounting plate with wiring showing
Josh Hendrickson / Review Geek

The most important thing you need to do before buying a smart thermostat is looking at your current HVAC system. There’d be nothing worse than doing a bunch of research and buying a smart thermostat, only to find out it doesn’t work with your current system. Many smart thermostats come with adapter kits that try to account for many scenarios, but it’s simply not possible for every smart thermostat to work with every home’s HVAC system.

There are a few systems that most smart thermostats in the US typically aren’t compatible with, including oil boilers, furnaces, baseboard heating, biofuels, or in-wall heaters. That said, you can find a smart thermostat for almost every system—you just have to know what you’re looking for. For example, homes with separate heating and cooling systems often won’t work with one smart thermostat, but you can work around this by buying a thermostat for each system.

When you’re shopping around online or in person, smart thermostats usually make it clear which systems they’re not compatible with. If you don’t see your type of HVAC system listed, you’re likely good, but you should always check the wiring behind your current thermostat. Before touching any wires, make sure you turn off power at the breaker to minimize electrocution risk.

After taking off your current thermostat, you should see some wires and letters. If you have a wire connected to the opening labeled “C,” that’s a C-Wire. Even if you don’t see a C-Wire that’s obviously matched up with its letter, there’s a chance you could still have a C-Wire installed but not currently in use. Most C-Wires are blue, or sometimes black, and you’ll likely see it loose among the bundle of visible wires.

Some smart thermostats come with a C-Wire adapter solution, so don’t fret if you can’t locate a C-Wire. Sometimes, there’s no need to buy a C-Wire when you can work with what you already have. For example, ecobee has a Power Extender Kit that lets you bypass the C-Wire requirement as long as your existing wiring setup consists of at least four wires.

When installing a smart thermostat yourself, there are a ton of helpful resources to help you out. Most smart thermostats come with a printed instruction manual, as well as step-by-step instructions in the app or on the thermostat’s display. Some companies also offer assistance over the phone if you run into any issues during the installation process. Then, you can always consult YouTube videos, online help articles, and—worst case—an industry professional.

At any point during the shopping or installation process, if you’re not comfortable with figuring out what type of HVAC system you have or whether or not you have a C-Wire, consult an expert! Even if it costs you a little bit of cash, it’ll save you the time of trying to figure everything out on your own. You can consult an HVAC technician to help you figure out which HVAC system your home uses, whether you have a C-Wire (and what wiring you do have if you don’t have a C-Wire), and install the smart thermostat once you’ve made your final decision.

Using the App and Your Preferred Virtual Assistant

Think about how you want to control your smart thermostat. Do you want to walk up to the physical thermostat on the wall and adjust your settings? Or do you want to use an app on your smartphone or voice commands to monitor your smart thermostat? Most people would probably lean towards using an app or voice commands for the sheer convenience.

If you think you’ll use an app all the time to control your thermostat, make sure it has an intuitive, user-friendly interface. All smart thermostats will have a companion app, but they might not all be good. When you’re looking at a thermostat, locate its companion app in the Google Play Store or the Apple App Store and read through its available features as well as user reviews. One user’s experience may not be the same as yours, but if you find multiple reviews saying the same thing, that’s not a good sign.


A good mobile app for smart thermostats will let you change the temperature within your home from anywhere, whether you’re at home or at the office. Then, you can typically use the app to view important data about your home’s HVAC system, like how much energy (and money) you’re saving, what you could do to save even more, when your air filter needs to be replaced, if there are any abnormal humidity or temperature levels, and so on. Many apps will offer all features for free, but some might hide advanced features behind a subscription paywall.

Most thermostat apps will be available to download on both Android and iOS devices, but not always. What you likely need to take a closer look at is which smart home ecosystems—Google Home, Amazon Alexa, Apple HomeKit, Samsung SmartThings, etc.—the smart thermostat is compatible with. If you want to use voice commands to raise or lower your home’s temperature, you’ll need the smart thermostat you choose to be compatible with your preferred smart home ecosystem that supports the virtual assistant you typically use.

Learning Features

Many smart thermostats have the ability to learn and adapt to your daily routine and temperature preferences. Once it learns your preferences, the thermostat can create a personalized schedule to automatically adjust your in-home temperature when you’re asleep or away. When done correctly, learning features can help you save energy and, therefore, money.

Some companies haven’t yet perfected their learning technologies, and depending on how much control you have over your thermostat within its companion mobile app, this could be a problem. When our editor-in-chief reviewed ecobee’s Premium Smart Thermostat, he mentioned how much he loved that ecobee’s Premium model didn’t learn. There’s AI tech built-in, but ultimately, you have control over the schedule you want to set.

This experience was drastically different from his experience with the Google Nest Thermostat, which seemed to “learn” that he wanted an uncomfortable house with some unbearable temperature. He would set the thermostat back to where he wanted it, and the Nest would change it back to whatever uncomfortable temperature it was at before.

On paper, learning features sound great. You install a smart thermostat, let it learn your preferences and habits, and the thermostat does all the energy-saving work for you. In reality, this isn’t always the case. Sometimes, learning features mean you have to fight your thermostat to convince it that it has learned something incorrectly.

If you want a thermostat with learning features, be sure to check out reviews that specifically mention a thermostat’s learning features. Reading someone’s hands-on experience with a thermostat’s learning features will often tell you more than a company’s marketing materials will.

Addition of Motion, Temperature, and Other Sensors

A smart thermostat is already smart enough on its own—hence, the name—but you can often make your setup even smarter by adding sensors. Many companies offer smart thermostat companion sensors, including standalone temperature or motion sensors for each room, sensors for your doors and windows, and specialty sensors that measure humidity levels or detect smoke.

Using these sensors in conjunction with your smart thermostat can help you save more money and energy. For example, if a door or window sensor detects that a door or window in your home is open, your smart thermostat can automatically shut off to preserve energy. Or, you can use a motion sensor to help the thermostat know when people are occupying a room. Then, in the winter months, your thermostat can heat up that room when people are in it and cut the heat when they’re gone to save energy.

Ecobee SmartCamera and various SmartSensors sitting on decorative display

While sensors add extra smart functionality to your thermostat, they’re not cheap. Depending on the company you’re buying from and whether you can get a discounted bundle of multiple sensors, each sensor could range from $30 to $50. It’s also important to note that not all smart thermostat companies offer sensors. So if you want to invest in sensors for extra functionality, double-check that the thermostat you’re looking at can be paired with sensors.

Convenience Features

People often invest in smart thermostats to make their lives easier, but not all smart thermostats come with the same helpful convenience features. The convenience feature you’ll see in most smart thermostats is geofencing, which essentially lets you set a virtual border, called a geofence, around your home and communicate your GPS location to your thermostat via your smartphone.

With geofencing, you don’t have to worry about adjusting your thermostat to save energy when you leave for work—and then changing it again when you arrive home—because your thermostat automatically does it for you. You can even set the geofence a few miles away from your home to trigger a pre-programmed routine, so it’s warm or cool enough inside when you get home.

Many smart thermostats also come with a vacation mode feature that lets you set the period of time you’ll be gone. Then, your thermostat will keep your home at a reasonable temperature for the season, but cooler or warmer than you might typically set the temperature when you’re home. For example, the thermostat will keep your home warm enough in the winter so your pipes don’t freeze and burst, but not a toasty 75 degrees because it’s not necessary. This saves you energy and money while maintaining a safe temperature inside.

Front view of Glas Smart Thermostat
Review Geek / Eric Ravenscraft

One feature that’s often overlooked but very nice to have, is a backlit display. While most smart thermostats have a backlit display, not all of them do. Some thermostats even have a built-in proximity sensor that causes the display to light up when it detects someone’s presence.

It’s also helpful to look out for thermostats that notify you when you need to change your air filter or when it detects a problem. As an example, a great alert system would let you know right away if your home’s temperature drops below freezing and it seems your heating system isn’t working while you’re on vacation. Then, you could have someone go check on your house and ensure the pipes don’t burst.

Choosing the Best Smart Thermostat for You

Deciding on the right smart thermostat isn’t an easy decision, but it’s worth taking your time and thoroughly researching your options. After all, your home’s heating and cooling system is something you use every single day. If you need some inspiration to help you start sifting through all the smart thermostats out there, check out the ones we think are pretty cool.

The Best Smart Thermostats for Automating or Controlling Your Home's Temperature

ecobee SmartThermostat with Voice Control - Programmable Wifi Thermostat - Works with Siri, Alexa, Google Assistant - Smart Thermostat for Home
Best for Full Control
ecobee SmartThermostat with Voice Control - Programmable Wifi Thermostat - Works with Siri, Alexa, Google Assistant - Smart Thermostat for Home
Google Nest Learning Thermostat - Programmable Smart Thermostat for Home - 3rd Generation Nest Thermostat - Works with Alexa - Stainless Steel
Google Nest Learning Thermostat - Programmable Smart Thermostat for Home - 3rd Generation Nest Thermostat - Works with Alexa - Stainless Steel
Honeywell Home RCHT8610WF T5 Smart Thermostat ENERGY STAR Wi-Fi Programmable Touchscreen Alexa Ready - C-Wire Required
Best Budget Option
Honeywell Home RCHT8610WF T5 Smart Thermostat ENERGY STAR Wi-Fi Programmable Touchscreen Alexa Ready - C-Wire Required
Sarah Chaney Sarah Chaney
Sarah Chaney is a professional freelance writer for Review Geek, Android Authority, MakeUseOf, and other great websites. She has a Bachelor of Arts in English with a Creative Writing concentration. Her degree, paired with her almost two years of professionally writing for websites, helps her write content that is engaging, yet informative. She enjoys covering anything Android, video game, or tech related. Read Full Bio »