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Last updated September 2026
Top Rated

Sensi Smart thermostat

A wide 5 inch LED display with on-device controls, supporting Apple HomeKit, Google Home, Alexa, SmartThings and Home Assistant.

4.4
23,041 ratings

#2 of the 16 thermostats we track, by rating

24% OFF
$129.99
$99.00
As an Amazon Associate I earn from qualifying purchases
Launch Year: 2016

Model: ST55

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Our review

Sensi Smart Thermostat Review: DIY Installation and Five Platforms, Without a Touchscreen

The verdict

The Sensi ST55 takes the opposite approach to most smart thermostats: instead of a glossy touchscreen it uses a wide 5 inch monochrome LED display with physical controls, and puts the money into compatibility and reliability. Platform support is the broadest in this comparison, covering Apple HomeKit, Google Home, Alexa, SmartThings and Home Assistant, and it includes on-device voice control. It measures temperature and humidity, supports manual and automatic scheduling with energy saving behaviour, and is designed for DIY installation. Warranty is three years. Remote room sensors are not supported, and Matter is absent.

Best for
  • Mixed-platform households
  • DIY installation
  • SmartThings and Home Assistant users
  • Straightforward, reliable heating control

Pros

  • Works with Apple HomeKit, Google Home, Alexa, SmartThings and Home Assistant
  • On-device voice control
  • Wide 5 inch display showing temperature and time, with physical controls
  • Temperature and humidity sensing
  • Manual and automatic scheduling with energy saving features
  • Designed for DIY installation
  • Three year warranty

Cons

  • No support for external temperature sensors
  • Monochrome, non-touch display that does not show weather
  • No Matter or IFTTT support
  • No proximity, occupancy or air quality sensing
  • No temperature alerts or system health monitoring
  • Trim plate costs extra
  • 2.4 GHz Wi-Fi only

Who is the Sensi ST55 for?

It is for someone who wants the thermostat to work with whatever they already have and to keep working without fuss. Very few thermostats support Apple HomeKit, Google Home, Alexa, SmartThings and Home Assistant simultaneously, and that list means the purchase is not a bet on one ecosystem. It is also built for self-installation, so the wiring job is designed to be done without an electrician. If you prefer buttons and a clear readable display over a touchscreen, that is a deliberate design choice here rather than a cost cut.

What it offers

Temperature and humidity sensing, manual and automatic scheduling and energy saving features, with the schedule visible on a wide 5 inch display that also shows the time. On-device voice control is included, which most competitors leave to a separate smart speaker. Physical controls mean adjusting the temperature does not require unlocking a phone or waking a touchscreen, which matters more day to day than spec sheets suggest. Three years of warranty is generous.

What to know before you buy

There is no support for external temperature sensors, so it heats based on where it is mounted and cannot balance a house where one room runs cold, which is the main reason to spend more elsewhere. The display is monochrome and not a touchscreen, and it does not show weather. Matter and IFTTT are unsupported. There is no proximity or occupancy detection, no air quality sensing, no temperature alerts and no system health monitoring. A trim plate is available but costs extra, so budget for it if your old thermostat left marks. Wi-Fi is 2.4 GHz only, and there is no speaker.

Is the Sensi ST55 worth it?

It is priced below the touchscreen competition and buys compatibility and simplicity rather than features. For a home with a single well-placed thermostat and devices spread across ecosystems, it is one of the safest choices available, backed by three years of warranty. If your house has a cold room, the lack of remote sensors is the reason to pay more for something else, since no update will add them.

Frequently asked questions

Which platforms does the Sensi ST55 support?

Apple HomeKit, Google Home, Alexa, Samsung SmartThings and Home Assistant, which is unusually broad. Matter and IFTTT are not supported.

Can I add remote room sensors?

No. External temperature sensors are not supported, so it uses the temperature at the thermostat itself.

Is it a touchscreen?

No. It uses a wide 5 inch monochrome LED display with physical controls, and shows temperature and time but not weather.

Can I install it myself?

It is designed for DIY installation, which is one of its selling points, though the job still depends on your existing HVAC wiring.

Does it have voice control built in?

Yes, on-device voice control is supported, though there is no speaker for spoken responses.

At a glance

Summary

Everything this thermostat supports, grouped by category.

Size & Materials
5.9 × 3.7 × 1 in (150 × 95 × 25 mm)
Included accessories
Trim Plate
Connectivity
2.4 GHz WiFi
Integrations
Google HomeAlexaApple HomeKitSamsung SmartThingsHome Assistant
Display
LED5"
Sensors
TemperatureHumidity
Scheduling
ManuallyAutomatically
Features
Energy SavingsDisplay TimeDisplay TemperatureVoice Control

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Company
Sensi logo

Sensi

4.4/ 5 avg ratingUSA flagHeadquartered in USA

Sensi, a brand of Emerson, makes smart thermostats focused on easy DIY installation and reliable HVAC control. Its thermostats offer scheduling, remote control and energy-saving features through the Sensi app, with support for Alexa, Google Home and Apple HomeKit on select models. Sensi appeals to homeowners wanting an affordable, easy-to-install smart thermostat.

Full specifications

Every spec, organized

Browse the full breakdown by category. Tap the on any row for what it means, or the for sources and documentation.

Size & Materials
Dimensions

5.9 × 3.7 × 1 in (150 × 95 × 25 mm)

Weight

?

Available in colors

NO

Included accessories
Trim Plate

YES (extra cost)

Temperature Sensor

NO

Connectivity
2.4 GHz WiFi

YES

5 GHz WiFi

NO

Bluetooth

NO

Z-Wave

NO

Zigbee

NO

Thread Protocol

NO

Integrations
Google Home

YES

Alexa

YES

Apple HomeKit

YES

Samsung SmartThings

YES

Home Assistant

YES

Matter

NO

External Temperature Sensors

NO

Display
Screen

YES

Screen Type

LED

Color Screen

NO

Touch Screen

NO

Screen Size

5"

Screen Resolution

?

Sensors
Proximity / Motion

NO

Occupancy

NO

Temperature

YES

Humidity

YES

TVOC

NO

CO₂

NO

Ambient Light

NO

Alerts
Temperature Alerts

NO

Air Quality Alerts

NO

Fire Alerts

NO

Intrude Alerts

NO

Scheduling
Manually

YES

Automatically

YES

Suggestions

NO

Features
External Temperature Sensors Selection

NO

Energy Savings

YES

System Health Monitor

NO

Display Time

YES

Display Temperature

YES

Display Weather

NO

Voice Control

YES

Speaker

NO

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