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Sensi

Sensi Smart Thermostat, Wi-Fi, DIY, Alexa, Energy Star Certified, ST55

Based on 23,118 reviews
Condition: New
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$89.99
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Availability: Only 9 left in stock, order soon!
Fulfilled by Bargain Shack USA
Arrives Thursday, Nov 5
Order within 11 hours and 47 minutes

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At a glance

Condition
New
Style
DIY
Pattern
Thermostat
Model
ST55
Screen size
5 in
Dimensions
1"D x 5.88"W x 3.75"H
Weight
11.68 oz
In the box
Thermostatfree mobile app2 AA batteriesmounting hardwarewire stickersinstallation guidewelcome guide with Sensi codewarranty booklet

Features 5

  • PRIVACY PROTECTION*: Sensi wont sell your personal information to third parties
  • EASY DIY INSTALLATION: Use the built-in level and step-by-step app instructions for a quick installation. Works with HVAC equipment found in most homes. Common wire (c-wire) is not required in most applications
  • SAVE ABOUT 23% ON HVAC ENERGY*: The ENERGY STAR-certified Sensi smart thermostat can help you save energy with features like flexible scheduling, remote access and usage reports
  • SIMPLE CONFIGURATION: Looks and feels like a thermostat. Has buttons and fits the same space as a traditional thermostat so you dont have to patch and paint your walls

Description

Sensi smart thermostats are designed for energy savings and data privacy – to give you full control of your home HVAC. With over 100 years of HVAC experience and manufactured by Emerson, you know our expertise already, even if you didn’t realize it. Emerson produces many of the HVAC parts that our smart thermostats control, so you can feel confident in the product you put on your wall. With our top-rated mobile app and easy installation process, customers of all comfort levels can make the switch to a Sensi smart thermostat. In addition, our customer service team of HVAC experts is always available to help you through any questions you might have. For more information on Compatibility, Energy Savings, and Privacy Protection, please refer to the “Product Documentation” section below.

Specs 34

Brand Sensi
Model Name ST55
Product Dimensions 1"D x 5.88"W x 3.75"H
Special Feature Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable
Additional Features Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable
Specific Uses For Product Air Conditioner, Boiler, Furnace, Heat Pump
Temperature Control Type Programmable, Smart/Remote
Connectivity Technology Wi-Fi

Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Thursday, Nov 5

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews

Fantastic for controlling multiple units!
Style: DIY Pattern Name: Thermostat
Purchased 7 of these for a church building. I got them specifically because of their ability to be controlled remotely via the Sensi software. Installation was very easy and except for one unit where I failed to go through the installation process from the beginning and assumed that unit functioned the same as the others, without any hiccups. Wiring instructions were clear and easy to follow. Connecting the units online and then controlling them as groups is fantastic. I highly recommend these thermostats! They are cost effective and function well. You can control them remotely AND lock out people from adjusting them via the front panel. Fantastic for commercial/public settings. I will be swapping out more units for these in other buildings. They also look good and are easy to program. ... show more
Reviewed in the United States on October 13, 2026 by cromsky
Easy and accurate
Style: DIY Pattern Name: Thermostat
This thermostat was incredibly easy to install and has already saved us a ton in just the first month or so. We purchased a new home in Minnesota but could not be there permanently for the first few months through March and April. In late March I installed this thermostat while at the house. The old dumb thermostat simply was running at a low temp while away which could have put the house at risk for cold weather. First off - Installation was simple. It took me about 10 minutes to install and it connected easily to our Wifi. I was able to set a couple different schedules and able to monitor them from our home in Colorado. I could see actual in home temps. See when the furnace was running and see outside temps forecast in the area. Upon return to our new home, I was able to use schedule which changed temps throughout the day based on our needs. I recommend this to our son and he installed one as well and loves it. A nice bonus was our local electrical company provide a nice rebate. I highly recommend. ... show more
Reviewed in the United States on May 14, 2026 by Dean Deick
Awesome Thermostat
Style: DIY Pattern Name: Thermostat
The setup was very simple with the Sensi app making it easy to setup going through each step in a detailed manner. The thermostat was replacing an older Emerson so the compatibility was smooth and easy transition. The backing plate, which mounts on the wall, is nice in that it has a built-in level indicator. The kit includes screws and anchors along with wire labels. The Sensi app makes connecting to WIFI and programming the 7-day schedule extremely simple. The layout of the physical thermostat is very straight forward with nice big buttons for temperature setting to changing from heating to cooling. The Sensi app is very intuitive when setting temperature controls. Overall, a very nice and simple thermostat which is simple to install. ... show more
Reviewed in the United States on September 11, 2026 by Rexer27
Step by step app is AWESOME!!!!! Install app BEFORE removing old thermostat.
Style: DIY Pattern Name: Thermostat
We've had this thermostat a month and I really like it so far. It makes me think our old thermostat wasn't actually working for a long time before it started setting itself to 85°. Since it wasn't even programmable, I knew it had to go and if I was going to upgrade I may as well go with something just a bit more...modern than a set-temp-and-it-stays-unless-you-change-it thermostat. I'm going to do pros and cons below. I do want to say, I took my old thermostat off the wall first, wrote down all the wire colors and the letter each was connected to on a piece of paper. The app removes the need for pen and paper. I just used my pen and paper to place the flags mentioned below on the correct wires. Pros: 1. This thing is super easy to install. Open the box and there are instructions for you to download the Sensi app. Once the app is downloaded it has you choose which letter slots you have wires connected to (R, RH, C, E, OB, etc.). The app then tells you how to use the flags they provide to label the wires. For example I had a wire that went into a slot labeled "R", but Sensi only had "RH" and "RC" (I think it was RC), so the app told me which R my wire needed to go in. Not having any electrical wiring experience, the app was SUPER helpful. It even had you take a picture of your wiring to save to your phone, just in case. 2. The piece that attaches to the wall has a built in level. I am super annoyed when things aren't straight on walls, so this right here, was awesome. 3. The app is really easy to set up. I just have a daytime and nighttime cycle, but I could set up all kinds of things super easily. Vacation modes, turning the AC up when I leave the house... It was great. It even walked me through how to sync the app with my Google assistant and the Samsung Smart Things app, which I didn't end up continuing to use. (See cons #1) 4. The report that tells you how long your AC is running is really helpful as well, especially since we had issues last year with it not being able to keep up. We have better insulation and updated windows and it's nice to see they are working, even when it's 99° with a heat index at 112°. (See cons #2) 5. I like that you can do things like temp and humidity offsets, have the AC turn on to help maintain proper humidity levels (we live in Florida, so this is a big thing for me), change the cycle rate (ended up choosing this one over another brand because people had issues with not being able to adjust the cycle rate on that one), and easily turn heat boost on or off. (See cons #3) Cons: 1. It doesn't work with Bixby. This is something I don't really understand, but I'm guessing they assume if you're gonna use Bixby you use Smart Things? But I can just use Google for that instead. 2. The recent usage section only shows how long the AC ran that day, not which times it ran or how long at a time it ran. It would be nice to see how long the AC was running at a time, especially in the afternoon when it gets really hot. I have not yet gotten a monthly report since I got the thermostat mid-June and it's now mid-July. Interested to see what the monthly report looks like at the end of the month. 3. Sometimes I had to change settings a couple times before they "stuck". I found after changing a setting I needed to wait a few seconds before returning to the settings menu and that helped. 4. Shortly after I got the thermostat the AC drain line clogged. This resulted in my app/thermostat constantly saying cooling was on, but the AC wasn't running. My usage for that day was like 21hrs, but I know it wasn't actually on for the majority of that. Not really a huge issue, but you won't have an accurate reading for that day. Summary: Overall, this is a really amazing unit and I have been really glad to have it. It was seriously a breeze to instakl and set up and functions well. I do wish I could connect it to Bixby without using Smart Things and I do wish I had a more detailed daily usage report, but those are very small inconveniences. I normally keep our house at 78° during the day and 77° at night and sometimes that feels cold. I would often feel hot before and wondered if our AC was not working correctly, but it would seem it was actually the thermostat. Very happy with this purchase. ... show more
Reviewed in the United States on July 18, 2020 by Brandi
Nice, but Alert values not adjustable
Style: DIY Pattern Name: Thermostat
Pros compared to similar Honeywell smart thermostat (Wifi circuit died after power flickers): - Displays humidity value on unit and in app (nice addition). - Physical installation was very well guided through app. - Lower current price. Cons: - If you want to get alerts in case the temperature/humidity at a remote property encounter problems, this might not be a good solution. The default values are: temp hi/low = 99/45F, humidity=70%. Per website: "High and low temperatures, as well as humidity smart alerts, are not adjustable." The app does display current temp/humidity, but this isn't sufficient for remote properties. (Will probably get a stand-alone monitor that has alert settings that can be adjusted.) - Initial connection/registration failed, followed by thermostat panel being locked for a while (which I didn't enable). Later attempt ended up working (using same credentials/code), and the the unit and app then worked normally. I like the unit (it did cover the previous unit's footprint, btw), but am a little disappointed. Hoping Wifi connection is reliable. ... show more
Reviewed in the United States on August 17, 2026 by TP
Excellent quality and easy to setup
Style: DIY Pattern Name: Thermostat
Review Image by KIM E.
Excellent quality and great price. Working like a dream. I replaced the previous old model with this Wi-Fi thermostat so I can control and monitor home temperature anywhere without being closed to it. Strong WiFi connection. I don't have any problem so far. It's easy to install, just unassembled the old one (don't forget TO TURN OFF the circuit breaker and take a picture of the wires connection BEFORE removing it), replace and reconnect all wires EXACTLY as the old one with this Wifi one. Download the app and follow the app instructions to setup and that's it. Hope it helps. ... show more
Reviewed in the United States on October 13, 2026 by KIM E.
Buyers Should Proceed with Caution
Style: DIY Pattern Name: Thermostat
After 3 hours trying to get the wifi to connect and subsequently waiting 40 minutes for support to answer the phone, the Agent sent this to try and rectify the issue: Thank you for contacting Sensi Technical Support. I apologize for this issue that you're having, but I can definitely assist you with a solution. It looks like your thermostat is having some trouble communicating through your router. Below are some router settings you can change to optimize connectivity. You may have to call your router's technical support service if you do not know how to make these changes. If your router is provided by your Internet Service Provider, contact them and they can remotely make these changes for you. • Update the firmware. Check to see if your router is running the latest firmware version available. o If you don’t see any firmware updates available on your router utility, make sure to check the manufacturer’s website for your specific model. They may have a firmware update available on their website. o If no updates have been available for the last couple of years, or if your hardware was manufactured prior to 2010, it may not comply with 802.11n standards. o If your hardware is provided by your Internet Service Provider, you may have to contact them to have your firmware updated. If no update is available from them, try resetting the router to factory defaults (see below).If that does not resolve the issue, ask to be provided with different hardware. • Reset your router to the factory default settings. It could be that some settings were corrupted over time because of electrical storms or power outages. Reference your router manufacturer’s instructions for assistance. *Please note, if you use a different SSID or passphrase after the factory reset, you will need to reconnect other devices to the network. • o Take note of your SSID (network name) and passphrase to reset after the factory default. o Set the security to WPA2 with AES encryption. o Set the 2.4GHz band to the 20MHz channel width. o Test to see if Sensi connects to your router. If it does, try adding back any custom settings to your router configuration. • Temporarily disable the 5 GHZ network, if you have a dual-band or mesh Wi-Fi network. This option typically can be found in the advanced settings of your router’s mobile app. Once Sensi is successfully registered and connected to Wi-Fi, you can re-enable the 5 GHz network. If you are still experiencing Wi-Fi issues, it may be necessary to separate your dual-band network. • Configure dual bands (2.4GHz and 5GHz) with different SSIDs/network names and passwords. This will allow you to connect the faster, higher data rate (streaming) devices on the 5GHz and keep the lower data rate devices (printers, thermostats, home automation, etc.) on the 2.4GHz. • Disable “MAC Address Filtering.” • Make sure your security is set to WPA2 with AES (CCMP) encryption. • Set the 2.4GHz band to the 20MHz channel width. • Consider using a Wi-Fi Analyzer app to see which channel (1, 6, or 11) has the least amount of traffic, and configure your router to a specific channel instead of "Auto." • Make sure the router is compatible with IEEE (Legacy) Power Save Polling. This is what the thermostat uses to stay connected to your network. • Sensi smart thermostat and Sensi Touch send TCP traffic on ports 80, 8091 and UDP traffic on port 8092. Sensi Touch 2 and Sensi Lite send TCP traffic on ports 8883 and 443. To receive over-the-air firmware updates, please make sure UDP traffic to port 8092 (34.233.82.197) and TCP traffic to port 80 (52.55.206.183) is open. For Sensi Touch 2, also make sure that TCP traffic to port 8883 (54.210.127.220) is open. This traffic needs to be able to navigate any network firewalls, proxies, or filter devices. This is insanity. All my other devices work fine off the gateway & router. The Agent gave up and told me to return the product - which will be done. How ... show more
Reviewed in the United States on July 20, 2026 by JKT
One of My Better Selections
Style: DIY Pattern Name: Thermostat
I love it. It was easy to install (even with my odd, 1960's wiring), is simple to operate, and looks great in its niche area. I've tested its accuracy and, temperature-wise, it's always right on the mark. The best part about it is that it's connected to the internet and, if I'm in the family room on the opposite side of the house and feeling warm, I just grab my phone and make the adjustment. No more running from one end of the house to the other! Also, if my phone is within easy reach, I simply tell Alexa to set the thermostat to whatever temperature and I don't have to exhaust my fingers on the phone. ... show more
Reviewed in the United States on September 17, 2026 by CliffCB
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