Honeywell Home T9 Smart Thermostat review: Remote sensors are the star attraction here

T9 isn’t the sexiest name for a new product, but most homeowners will be familiar with the Honeywell brand (now Honeywell Home, after its parent company spun off its residential division as Resideo Technologies in late 2018). More importantly, the Honeywell Home T9 Smart Thermostat is a big step up from anything the company has offered in this space to date.

The T9 also shows how much this company has learned from its much smaller competitors, particularly Ecobee and Nest Labs. Honeywell Home’s new thermostat doesn’t have Alexa onboard, like the Ecobee4, or a behavior-learning algorithm like the Nest, but it does have all the rest of the features and performance we’ve come to expect from a modern connected thermostat. It’s also the first Honeywell consumer product to support remote sensors, so that it’s aware of the temperatures in more locations inside your home than just the hallway or other out-of-the-way location where it happens to be installed.

Ecobee was the first to offer such a feature, currently in the Ecobee4 (our top pick in this category), and Nest Labs added sensor support for its third-gen Nest Learning Thermostats in mid 2018. Honeywell’s sensors, however, are the best we’ve tested.

Inoffensive industrial design

The T9’s rectangular shape doesn’t do much to move the needle in terms of design; on the other hand, it’s not at all edgy. It resembles the Honeywell Lyric T5 (our current favorite budget-priced thermostat), but is more aesthetically pleasing, with a white bezel surrounding a bright white 3.5-inch touchscreen. Colored text displays the current indoor temperature (orange while heating, blue while cooling) and gray text shows the current time the temperature outside. Icons report on weather conditions.

The thermostat’s home screen displays the current indoor and outdoor temperatures along with icons to indicate the current weather conditions. Tap its screen and you’ll get be presented with more detailed information about the heat-to and cool-to temperature targets you’ve set, along with an indoor humidity reading (but you’ll need to step up to professionally installed Honeywell Home T10 Pro if your HVAC system includes an integrated humidifier). You can access every option and feature, including scheduling, from the thermostat’s own user interface, so you’re never reliant on its accompanying mobile app.

Users upgrading from a previous Honeywell T-series thermostat won’t need to do much more than snap the T9 into the existing wall mount because the wiring contacts are the same. For those moving from anything else, installation is still easy enough: Mark the screw holes for the new mounting plate, connect the wires, secure it, and stick the thermostat onto the plate. Resideo also includes a power adapter for installs where a C (common) wire is not present.

The T9 then guides you through its setup process directly and you can connect to the app right then or later. One point of confusion, however, might be picking the correct app from your app store. Previous Honeywell smart thermostats used the Total Connect Comfort app, which has since been superseded by the easier-to-remember Honeywell Home app. The app’s name was changed to Resideo in 2022.

You’ll program the Honeywell Home T9 in a conventional manner, establishing a weekly schedule with as many (or as few) temperature changes as you like. It’s very easy, for example, to establish one temperature target for a 10:00 p.m. bedtime, and a second one for 8:00 a.m. when you anticipate starting your day, plus third and fourth targets for when you leave and arrive home from work.

You can program the same schedule for multiple days, or create a custom schedule for every day of the week. The T9 also supports geofencing, so that your HVAC system will be automatically set to different temperature targets when you leave home and come back again.

It’s all about those sensors

But occupancy sensor support is easily the Honeywell Home T9’s most important feature. You can buy the thermostat without any sensors for $169 and add them later for $40 each on Amazon, but most people won’t want to—especially since the $200 thermostat-and-sensor bundle gives you a $10 discount over the price of buying the two components separately.

These small square devices are outfitted with motion, temperature, and humidity sensors along with subtle indicator LEDs. You can deploy up to 20 of them, which should be enough to cover every room in the average home. They’re powered by two AAA batteries, which Resideo says should last for one year.

The thermostat will then endeavor to have your HVAC system cool or warm your home until the occupied rooms reach the programmed target temperature. You can also set different temperature targets for each room that’s served by a sensor and select which rooms should have priority. In this scenario, the thermostat will average those numbers and set that as the target temperature for the entire home.

These Honeywell Home sensors, which use proprietary radios operating in unlicensed 900MHz radio spectrum, deliver the best range I’ve seen in this class of product. They had no problem staying connected in rooms in my home where both Ecobee’s and Nest’s sensors simply didn’t work. The company says they offer range of up to 200 feet from the thermostat, and in my experience, they were much better at penetrating walls and other obstacles than what the competition has to offer.

Curiously, the thermostat itself does not have a motion sensor. If it’s installed in a room where you want temperature control based on occupancy, you’d actually need to deploy a sensor there, too. I also encountered an oddity with the Honeywell Home app: It doesn’t report sensor status changes—such as a location change—while you’re actively monitoring the sensor itself. The app didn’t report a change from unoccupied to occupied, for example, when I entered the room while looking at the app. I had to exit out to the app’s main screen and then navigate back to that sensor’s window to see its current state. This was the case for any data readings that changed while I was monitoring a given sensor.

Smart home integrations

If you’re looking for a thermostat that you can integrate with your smart home system, the Honeywell Home T9 supports Samsung SmartThings and IFTTT, and it’s compatible with Amazon Alexa, Google Assistant, and Microsoft Cortana. Once connected, you can check the temperature of any room with a sensor (although strangely, not the humidity level) and even command the assistant to adjust the temperature of any given room. Apple HomeKit support is in the works (the earlier T5+ and T6 Pro already support HomeKit, so this shouldn’t be a big hurdle). You’ll find a complete third-party support list here.

The Honeywell Home T9 isn’t the prettiest or most high-tech smart thermostat on the market. We still prefer the similarly Ecobee4 for its integrated smart speaker, and the third-generation Nest Learning Thermostat remains the most beautiful device in this category (and it’s the best choice for those deep in the Nest ecosystem). But the way the T9 works in conjunction with its room sensors puts it up high on our list of recommended smart home devices for anyone moving up from a conventional thermostat.