Smart thermostats make it easy to control your home’s heating and cooling system from just about anywhere, and the Sensi Touch Smart Thermostat ST75 ($169) is no different, but in addition to phone and voice control, it offers a responsive color touch-screen control panel. Easy on the eyes and simple to install, the ST75 is a bit more expensive than our Editors’ Choice winner for affordable thermostats, the $129.99 Nest Thermostat. That said, the Sensi model adds support for Apple’s HomeKit and Samsung’s SmartThings home automation platforms, as well as native Siri voice control, making it an excellent alternative to the Nest Thermostat if you use any of those systems.
ST75 Design and Features
Available with a glossy black or glossy white finish, the ST75 is an attractive thermostat. It has a very thin clear bezel around its 4.2-inch full-color touch-screen control panel, and measures 3.4 by 5.6 by 1.0 inches (HWD) overall. It comes with mounting hardware, a welcome guide, an installation guide, and labels to identify your HVAC wires, and it’s equipped with an embedded Wi-Fi radio for connecting to your home network.
The ST75 is compatible with single-stage and multi-stage oil, gas, and electric HVAC systems and systems with central air and heat pumps. It requires a “C” (common) wire, so if you live in an older house, make sure your thermostat wiring uses a common wire for power. The thermostat works with Apple’s HomeKit platform and Samsung’s SmartThings home automation system, and it can be controlled using Amazon Alexa, Apple Siri, and Google Assistant voice commands. However, it doesn’t work with IFTTT applets that allow it to interact with other IFTTT-compatible smart home devices.
The thermostat supports geofencing and will adjust your heating/cooling settings based on your location. You can have the thermostat send push alerts when your home’s temperature and humidity levels reach a certain threshold, and have it alert you if there are heating and cooling issues. You can create a custom 7-day heating and cooling schedule using the intuitive touch screen, or you can use the Sensi mobile app for Android and iOS devices. As with the Nest Thermostat, the ST75 lacks the remote room sensors that you get with more expensive thermostats, such as the $249 Ecobee Smart Thermostat With Voice Control.
Programming the ST75 is easy thanks to its touch-screen panel. It remains dimmed until you touch it, when it lights up and displays the current room temperature in large white numbers in the center against a gray background. The background turns orange when actively heating the house and blue when cooling. Off to the right is the Set To temperature, with up and down arrows for changing the temperature setting. To the left is the current temperature, and just below that is the room humidity reading. At the very bottom of the screen are operating mode (heat, cool, off, aux, auto) and fan mode (auto, on) indicators.
The Menu button in the top left corner takes you to a screen where you can access settings and options. Here you can adjust Sleep mode settings, turn on a back-glow LED for extra lighting around the thermostat, toggle Wi-Fi on and off, set the current date and time, and create heating and cooling schedules for each day of the week. Use the Advanced Settings button to configure dehumidifier and circulating fan settings.
The mobile app lets you do everything that the touch panel does and more. It opens to a screen that shows the current temperature and humidity, and has set point arrows off to the right. At the top of the screen is your local weather with high and low temperatures, and along the bottom are buttons for Mode (heat, cool, off), Fan (on, auto), Schedule, and Usage. Use the Schedule button to create heating and cooling schedules, and tap the Usage button to view daily and monthly usage reports.
Other controls allow you to set temperature setpoint limits, enable geofencing, edit your account information, change passwords, set up email and push notifications for important reminders (filter changes, HVAC maintenance, humidifier pads) and system issues, and access the online help center. Here you can also look for and sign up for energy-saving programs, receive new program notifications, and check the thermostat’s firmware version.
Installing and Using the ST75
As with most smart thermostats, installing the Sensi ST75 is relatively easy, but it does require working with low-voltage wires. If you’re not comfortable working with electrical wiring, you may want to find someone who is, or hire a professional to do the job for you.
I started by downloading the app and tapped Install Sensi Thermostat With HomeKit, which tells the app to use your existing HomeKit data and Wi-Fi information (you can also choose to create an account and set the device up manually if you don’t use HomeKit). I selected the Touch Thermostat from the list and was presented with a screen telling me what tools I would need (screwdrivers, a drill, and wire strippers). At this point, you can opt to watch a video tutorial showing you how to install the thermostat. I tapped Next and followed the instructions to turn off power to my thermostat at the breaker and remove my old thermostat’s cover. I took a picture of the wiring, disconnected the wires, and removed the mounting plate. In the terminal screen, I selected the terminals that had wires attached to them and then selected my furnace type (gas electric, boiler/radiant). I labeled my wires before disconnecting them from the old terminal, and removed the terminal base.
Using the included mounting screws, I attached the ST75 terminal base to the wall and connected the wires. The base has a neat LED terminal light that helps you see what you’re doing. Once the wires were connected, I snapped the thermostat onto the base and restored power to the circuit, at which point the touch screen lit up and displayed the main control screen. I tapped the Menu button in the upper left corner of the screen, selected Wi-Fi, and scanned the HomeKit code using my phone’s camera. After 30 seconds, the thermostat was connected to my home Wi-Fi and I gave it a name and location. I created a Sensi app account, registered the thermostat, and the installation was complete.
The ST75 worked well in testing. The touch screen is responsive, bright, and easy to navigate. The thermostat responded quickly to temperature changes using the app and the touch screen, and always adhered to my schedules.
Alexa and Siri voice commands to raise and lower the set temperature and turn the thermostat on and off worked as intended. So did the geofencing feature, which sets the thermostat temperature back three degrees when you leave a certain perimeter.
A Super-Versatile, Relatively Affordable Smart Thermostat
If you’re looking for an affordable smart thermostat that works with multiple voice control and home automation platforms, put the Sensi Touch ST75 on your short list. It’s easy to install and offers a responsive touch screen for viewing temperature and humidity readings, and programming heating and cooling schedules. You can also control the ST75 with your phone, with Alexa, Google, and Siri voice commands, and as part of your HomeKit or SmartThings home automation system. If you require an affordable thermostat that will interact with numerous third-party smart devices, our Editors’ Choice, the Nest Thermostat, works with IFTTT applets and is around $40 less. But if you need a thermostat with HomeKit and native Siri support, the ST75 is a terrific alternative.
