Honeywell Thermostats

Review: Honeywell T9 thermostat is capable and affordable with just a few annoyances

Short version: The Honeywell T9’s got all the bells and whistles at a surprisingly low price. We rate it a Smart Buy.

Honeywell T9 thermostat in "heating mode" with an orange screen. The smartphone app is pictured on an iPhone held adjacent to the thermostat.
Pictured: The Honeywell T9 as it heats our home, next to the companion app showing the same information on the phone screen.

Honeywell finally nails it

The T9 lands like Honeywell’s heartfelt apology for their previous missteps in the smart thermostat market. Honeywell’s now-retired Lyric model was a mess back when we tested it and the app setup for the Honeywell RTH6580WF included an arduous account setup process that was all but impossible to complete on a mobile device.

Fortunately, Honeywell – technically Resideo, a spin-off of Honeywell – has upped its design game with the T9 and this old-timer is ready to forgive.

Quick Look

Honeywell T9 Smart Thermostat


  • Extensive HVAC system compatibility
  • C-wire kit included
  • Priced significantly less than many competitor models
  • Clean and simple design
  • Sensors can monitor humidity


  • Narrow design may not cover old thermostat holes, no backplate included
  • No control over humidity
  • Schedule OR geofence, pick one
  • Sensors have to be mounted to wall and cannot stand alone

You can buy aHoneywell T9 with or without the room temperature sensor accessory included.

See it on Amazon:

About Us

We are independent and unbiased home automation enthusiasts who buy, try, and review smart thermostats with our own funds (no freebies). Photos are our own unless otherwise noted. We source opinions from local HVAC installers and friends and family who are long-term users of various smart thermostats. This review is intended for visitors in the US and Canada. We hope you find our site useful and we welcome your comments and corrections.

Honeywell T9 look and feel

Overall, the T9 looks very nice. It’s no larger than it has to be and the screen is responsive, bright, and uncluttered. The current temperature is displayed large, and the “raise temp” and “lower temp” buttons are large enough to tap.

Honeywell T9 thermostat pictured in the center of the photo. The current temperature, "74 degrees" is shown in the center of the screen.
The unit itself is bright, with big numbers. I do wish the humidity percentage was displayed in a larger typeface, though.

The screen takes on an orange/yellow background color when your HVAC system is actively heating your home, and a blue background color when the system is actively cooling your home, making it obvious at a glance what the unit is doing.

Honeywell Home app pictured on a smartphone screen with the Honeywell T9 thermostat in the background.
The T9’s companion app uses similar user interface conventions to the unit itself.

Also included: a Honeywell-branded wiring adapter.

Honeywell Home wiring adapter pictured over a white background.
Pictured: The T9’s included Honeywell adapter installs inside the furnace to emulate the needed C-wire.

If your HVAC system lacks a C-wire (you have 4 wires instead of 5), you can install this adapter inside your furnace to make your existing 4 wires act like 5. Think of it as making one of the existing wires emulate the behavior of a C-wire. This is very similar to the Venstar Add-a-Wire adapter we’ve recommended for years.

Honeywell’s adapter can also be bought separately.

Note: check compatibility before buying. See Honeywell’s informative article on the topic.

Honeywell T9 Compared to Ecobee and Nest

Overall, we think the Honeywell T9 is competitive with even the top-of-the-line models from Ecobee and Nest. It’s easy to program, the sensor is useful, and it’s easy to control it from the app. For 95% of what you want to do with a smart thermostat, the T9 has you covered.

For everything else, see our breakdowns by category:

Price and value: 5/5

With an MSRP of $149.99 ($179.99 with sensor) the T9 is priced noticeably lower than current models from both Ecobee (read our SmartThermostat review) and Nest (read our “Learning Thermostat” review) with no real sacrifices. If you’re setting up a multi-zone home, the savings add up quickly.

Look and feel: 4/5

The Honeywell T9 looks just as nice as the competition and, in some ways, is easier to use.

For example, the T9 has distinct “up” and “down” buttons for making temp adjustments on the device’s touch screen, as opposed to Ecobee’s sometimes-awkward slider. However, the Honeywell T9 is only available in stark white, compared with Ecobee’s sleek black and Nest’s myriad ring color choices.

Installation and setup: 5/5

The Honeywell T9 was just as easy to install and set up as an Ecobee or Nest thermostat. As a bonus, the Honeywell T9 comes with a C-wire kit you can use in the event that your HVAC system lacks this wire. The Ecobee also comes with a kit of its own, but Nest thermostats do not.

Remote temperature sensors: 4/5

Honeywell sensors can read humidity, which is something Nest and Ecobee sensors don’t do, but the T9 itself cannot control your humidifier.

The Honeywell sensors have to be mounted to a wall, which we didn’t like – we have enough holes in our walls – and we’re well-aware that Ecobee’s sensors come on little stands that make it easy to position them anywhere in your house.

Scheduling: 4/5

Pick one: a schedule or geofencing. (See also: What is geofencing?)

The T9 makes no attempt to “learn” your schedule like the Nest offers or act on “hunches” like Amazon’s own thermostat, but the included room sensor can be used to determine if you are home and where you are in the home.

We dinged the T9 in this category because you can only have a set schedule or geofencing, not both at the same time. It’s easy to program in a day-by-day schedule, though, and that’s what we usually rely on.

Compatibility: 4/5

The Honeywell T9 works with:

  • A huge variety of 24v HVAC system setups
  • Amazon Alexa, Google Home, Apple HomeKit, Samsung SmartThings, Apple HomeKit (as of November 2021)

The Honeywell T9 does not work with:

  • Humidifiers
  • Line voltage systems, electric baseboard heat (120-240V) and millivolt systems
  • Some home routers that combine the 2.4Ghz and 5Ghz bands into one network (you might be able to adjust this in your router’s settings, also see Honeywell’s troubleshooting article)

One thing that bugged us: the T9 is tall and narrow, and none of our old screw holes were useful (or even covered) by the device. Some thermostat makers solve this by offering a backplate, but the T9 doesn’t come with one.

Reasons to get a Nest instead of Honeywell T9:

  • You prefer Nest’s “look and feel” or you already have other Nest products you want to integrate with

Reasons to get Ecobee instead of Honeywell T9:

  • You have other Ecobee products
  • You like the idea of having Alexa built into the thermostat itself

Honeywell T9 unboxing

The contents of the Honeywell T9 retail box. Pictured items include the installation guide booklet, the thermostat unit itself, the backplate, the wiring adapter, the sensor, and mounting hardware.

Included in the box:

  • Honeywell T9 thermostat unit
  • Honeywell-branded power adapter kit
  • Honeywell room temperature sensor + two batteries for it
  • Backplate (mount this on the wall and hook the wires up to it)
  • Mounting hardware for the backplate
  • Instruction manual

Honeywell T9 installation and setup

Installation is straightforward and took us fewer than 30 minutes, but we had already verified we had suitable wiring prior to this step.

We highly recommend looking behind your existing thermostat (just pop it off its backplate) and seeing what kind of wires are back there before you commit to removing your existing thermostat.

  1. Cut power to your existing thermostat
  2. Remove your existing thermostat and unscrew its backplate
  3. Mount the Honeywell back plate in its place
  4. Connect the wires (more photos on that later)
  5. Click the Honeywell T9 into place
  6. Turn power back on and follow on-screen setup instructions
The Honeywell backplate in front of drywall with multiple holes already drilled in it. The photo shows how the backplate does not line up with previously-drilled thermostat mounting holes.
Pictured: Honeywell T9’s backplate is narrower than previously installed thermostat’s backplate. Time to drill more holes! Also, there’s no decorative backplate included to cover these holes.
A photo of the T9 Thermostat's installation guide booklet, and the T9's backplate mounted on a wall.

Once the thermostat unit is connected and powered on, a series of on-screen prompts will guide you through the rest of setup.

The only question we thought might be confusing was the one about Furnace Type. If you choose gas furnace you’ll be asked to verify whether it’s a High Efficiency furnace or Standard Efficiency furnace, and “last 10 years” is kind of vague.

The most sure-fire way to answer this question is to look at the sticker that contains the model number of your furnace and look for a “%” or “AFUE”, which stands for “annual fuel utilization efficiency”. A higher AFUE means a more efficient furnace, and any furnace with 89% o higher AFUE is considered high efficiency.

If you can’t find this number, consider searching for the model number of your furnace to find its manual or, if you know the furnace is older than 15 years or so, standard efficiency is a safe guess.

A close-up photo of the Honeywell Home's screen. The set-up screen is asking for "Furnace Type", and the choices are "High Efficiency" and "Standard Efficiency".

Continuous power source (C-wire) required

If you don’t have a C-wire, the Honeywell T9 provides a power extender kit that you install in your furnace to add that functionality to your existing wiring.

Covering every possible wiring scenario is out of scope for this article, but for help with the extender kit or to see if you need it, Honeywell provides a lengthy help article here.

Scheduling the Honeywell T9

Programming a day-by-day schedule for the T9 is simple and fast, especially when compared with the difficulty of setting a daily schedule on some older programmable thermostats. This was our preferred way of scheduling the T9.

However, just like Ecobee and Nest thermostats, the T9 offers some alternatives to setting up a schedule.


A geofence is an invisible “border” (you can adjust it) around the vicinity of your home. When you’re outside the border, the thermostat realizes it and stops acting like you’re home. When you return to the inside of the border, you’re considered to be “home” and the thermostat starts heating/cooling your home to your preferences.

The T9 makes you choose between setting a schedule or relying entirely on the geofence. You cannot mix the programmed schedule and the geofencing, so if you deviate from your programming (ie: you’re home on what’s normally a work day) and you’re technically inside the geofence, the T9 won’t figure it out – you’ll have to manually override the program.

This feels like the T9 is missing out on an obvious advantage to having a smart thermostat: I want the thermostat to be smart enough to figure out I’m home this Friday even if I’m normally not home every Friday and heat/cool accordingly.

Caveat: everyone who lives in your home will have to install and set up the Honeywell app on their smartphone to participate in the geofencing.

What the sensors can do

Think of the smart sensor as another set of data points the thermostat can collect about your home. The sensors can read temperature and humidity, but unlike Ecobee and Nest sensors, they do not detect occupancy.

A hand holding a Honeywell Home smart sensor device.
Pictured: Honeywell T9 room temperature sensor prior to installation

The intended use case for the sensors is to prioritize the comfort of one room over the comfort of other rooms. For example, at night you might only care about the temperature of your bedroom, not the temperature of the rest of the house. You can have the thermostat only look at what temperature reading the bedroom sensor is getting and run the heating/cooling based on that information.

Another good use case: if your thermostat is in an awkward location (maybe a hallway that’s always cold, or across from a window you like to keep open during the day, or in the sun) you might be used to compensating for excessive heating/cooling delivered to the rest of the house based on the thermostat’s reading. With a sensor, you can place the sensor where you wish the thermostat was taking its readings from (perhaps your bedroom or home office).

One thing we didn’t like: the Honeywell sensors can’t stand on their own, you have to mount them to a wall. A 3M strip is included but we’ve been disappointed by sticky strips in the past (the thing they’re holding up inevitably falls down), so we went with the “mount it on a nail” approach.

The Honeywell T9 comes with one sensor, and you can buy additional ones either alone or in a two-pack at a reasonable price. They run on two AA batteries that last about a year.

Other things to keep in mind:

  1. The Honeywell sensors are just sensors, and can’t be used to create more sophisticated automation routines throughout your home.
  2. No thermostat on the market is capable of maintaining different temperatures in different rooms. If getting the room you’re in to be comfortable normally means making other rooms excessively cool or hot, the same will happen with a sensor-based system.

The bottom line

We think the T9 shines for homes with multiple zones, where the savings will add up fast with each additional thermostat purchased. We thought the sensors weren’t quite as sophisticated as some of the competition’s sensors, but we appreciated the humidity readings. The inability to override programmed scheduling with geofencing or “Hey, I’m home!” sensor data feels like a missed opportunity for the thermostat to feel “smarter”, but if you’re the type that likes to set a schedule and call it good, you’ll appreciate the ease of scheduling the T9. We also like that you can buy the thermostat without the sensor included and save about $30 in doing so.

The short of it

Honeywell T9 Smart Thermostat

All the good stuff at a low price

The Honeywell T9 has all the popular smart thermostat features, an easy to use app, and supports a wide variety of HVAC configurations.

Review Date
Reviewed Item
Honeywell T9 Thermostat
Author Rating
Product Name
Honeywell T9 Thermostat

One reply on “Review: Honeywell T9 thermostat is capable and affordable with just a few annoyances”

The T9 sensor readings are not readable on the sensor or the app….or the stat base. Why buy 2 sensors if you cant see what they are doing??? The Ecobee shows all sensor readings! That makes more sense to me!!!

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