---
product_id: 43173735
title: "Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55"
brand: "emerson"
price: "$195.92"
currency: USD
in_stock: true
reviews_count: 8
category: "Emerson"
url: https://www.desertcart.us/products/43173735-emerson-sensi-wi-fi-smart-thermostat-for-smart-home-diy
store_origin: US
region: United States of America
---

# 5" LED Display Wi-Fi Connectivity Data Privacy Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55

**Brand:** emerson
**Price:** $195.92
**Availability:** ✅ In Stock

## Summary

> 🌍 Smart Living Made Simple!

## Quick Answers

- **What is this?** Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 by emerson
- **How much does it cost?** $195.92 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/43173735-emerson-sensi-wi-fi-smart-thermostat-for-smart-home-diy)

## Best For

- emerson enthusiasts

## Why This Product

- Trusted emerson brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Sleek Design:** Fits perfectly in your existing thermostat space.
- • **Seamless Integration:** Compatible with Alexa and other smart home systems.
- • **Effortless Installation:** DIY-friendly with step-by-step app guidance.
- • **Energy Savings Champion:** Save up to 23% on HVAC energy costs.
- • **Smart Maintenance Alerts:** Receive timely reminders for optimal HVAC performance.

## Overview

The Sensi Smart Thermostat combines 100 years of expertise with cutting-edge technology to offer a user-friendly, energy-efficient solution for modern homes. With easy DIY installation, robust data privacy, and compatibility with popular smart home systems, it’s designed to enhance your living experience while saving you money.

## Description

DIY your smart home with the Sensi smart thermostat. Compatible with most residential HVAC systems — no common wire (c-wire) required in most applications. You can trust Sensi as we do not sell your personal information to third parties. And Sensi comes with the dependable performance and reliability you can count on from our 100 years of HVAC experience. With our top-rated mobile app and easy installation process, customers of all comfort levels can make the switch to a Sensi smart thermostat. For more information on Compatibility, Energy Savings, and Privacy Protection, please refer to the “Product Documentation” section below.

Review: Fairly east to set up, works well with Google Home - (Long, but I hope worth the read) Overall, I am extremely happy with the Emerson Sensi smart thermostat. For me it was a pretty easy project, but it is important that you know what type of cooling/heating system you have prior to attempting the installation. Although the basic installation is made very simple using the Sensi app, there were some very important things not covered. I suggest you check out how to configure your Sensi on their site (Configuring Thermostat | Sensi US (emerson.com)). I’m a pretty good DIYer, but have very little experience with AC/heating systems. I was 99% sure I had a heat pump setup, but I called a local AC technician I know to confirm and am glad I did. Having installed a few smart thermostats, to include this one, he not only confirmed I had a heat pump, he also informed me I would have to go into the system settings on the thermostat and change the outside setting from ‘AC1’ to ‘HP1’. This was confirmed when I checked out the Sensi website. Armed with this information, installation went without a hitch and I was up and running in no time. Pros: - Easy to install, if you have a little DIY experience, all the information needed concerning your AC/Heating system and gather the additional information before starting. - Very easy to connect to WiFi and integrate with Google Home. Connected to my WiFi with in seconds following the instructions; when I opened my Google Home app, there was an icon to add Sensi, clicked on it and moved the thermostat to the appropriate room. I have not experienced any drop-offs or loss of the WiFi, even when I turned off my WiFi for a few hours, removed the batters or installed old, weak batteries as tests; in every case, the thermostat remained connected or automatically connected right back up in seconds with no need to go through the WiFi setup operations again. - The Sensi app, in addition to walking you through the installation, allows you to set up various cooling/heating programs to run automatically, as well as change other settings. Once added to Google Home, you can switch programs (cool, heat, auto), turn it on/off and set the temp. You can also use voice commands through Google to do this as well. - The ability to adjust the thermostat to compensate for temperature offsets. In my case, where my thermostat is located the temp registers about 3 degrees off from what it is in our master bedroom or living room. I simply adjusted the offset in the Sensi app to compensate for this and now our bedroom and living room remain closer to the set temp then they have in the past. - It can be operated manually by those less tech savvy. The controls on the face plate look and operate like those on our old ‘conventional’ one. I also like that you can lock out the manual operation from the app so that no one else can mess with the settings; like during the holidays when you have family members over who feel they can change the settings without asking .. lol. - Being able to adjust the system cycling rates. There are three settings (short, medium, and long) that can be set independently for heat, heat aux and cooling. I don’t mind having my temps vary a degree before the system cycles back on, so I have all mine set to long; during the summer, I may switch cooling to short to see how much of a difference it makes. Con: I only have one and it is the reason for my 4 rating. The instructions, at least those in the box, should include information on the additional settings that may need to be needed depending on the AC/heating system you have. At a minimum, they should inform you that you may need to make additional setting changes and where to find the instructions online.
Review: Works with boilers and does NOT require a C-wire - I moved to the East coast last December. We have a six-zone boiler heating system with baseboard heaters throughout 4,200 sq. ft., on three floors (not bragging, just trying to give an idea of the size and complexity of the system). With six old-school manual thermostats spread throughout the house, it was nearly impossible to evenly regulate the heat during the cold winter, so some rooms were very cold and others too warm. I found myself constantly going up and down stairs to monitor temperatures and make sure I wasn't wasting heat or keeping areas too cold that would affect other zones. My boiler was installed in 2007, so it isn't very old and it's very efficient. However, it's a two-wire system with no C-wire, so the fact that 99.9% of "smart" thermostats on the market require a C-wire to operate was very frustrating. I stumbled across the Emerson ST55 and saw in the description that it could work either with or without a C-wire, so I called Emerson tech support to make sure before I plunked down hundreds of dollars on six thermostats that might not work. Tech support confirmed my fears that it would not work without a C-wire despite the desertcart description, so I kept hunting. Fortunately I found a YouTube review of the ST55 and the owner said he had been successfully using it with the same kind of two-wire system that I have for over two years. So I figured I'd buy one and see if it worked. Worst case, I'd send it back for a refund. The instructions inside the box clearly state that it will not work without a C-wire, but I ignored them and kept going. With only two wires it was a breeze to install. I put in the batteries, snapped it into the wall plate, downloaded the app, created an account and was ready for testing in about 15 minutes. I'm not sure if it's just my system or all boilers, but I didn't realize it doesn't turn on instantly when the thermostat temperature is raised above the existing temperature. So when I first tested it, I was bummed that it didn't work. But as I walked downstairs to the boiler, it was running! So I did some more testing, and found that there's about a 20-25 second delay between increasing the temp and the boiler kicking in. Granted it's only been a couple months since I got it, but I've played with it plenty and it's working great. Instead of a C-wire, the thermostat is powered by two AA batteries. The guy in the video said he's been using the same regular alkaline batteries for two years and they're still at 90% charge capacity, which is awesome. But I figure that even if I have to replace batteries every year, 12 AA batteries is a helluva lot cheaper than paying an electrician to rewire all six zones! On top of the six heat zones, I also have two central AC units. Thankfully those have C-wires, but I'm going to replace those thermostats with the Emerson ST55 also so that I'll have full control of all heating and cooling from one simple-to-use app. With any luck it'll go on sale on Prime Day so that I can save some money! :-) I can't speak to the Alexa integration as I don't use that functionality. But plenty of other reviewers have said it works fine. I appreciate Emerson's thoughtfulness in adding a built-in level to the back plate. I'm a stickler about things being mounted straight, so it was nice to not have to break out a level to make sure I didn't mount it crooked. As for aesthetics, the ST55 is nice. It's not too large to look obnoxious, but it has a good-sized display. And I'm not sure if it's just because I'm running it on battery, but the back light doesn't stay on constantly, so it doesn't light up a dark room at night (not too important in common areas, but important if you've got a thermostat in a bedroom). So, to make a long story short, don't believe Emerson. This thing really does work on a two-wire boiler heat system with no need for a C-wire!

## Features

- PRIVACY PROTECTION*: Sensi won’t 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
- SMART MAINTENANCE: Sensi can help monitor the performance and efficiency of your HVAC system by delivering valuable usage reports, alerts about your equipment, and maintenance reminders like filter replacement
- SIMPLE CONFIGURATION: Looks and feels like a thermostat. Has buttons and fits the same space as a traditional thermostat so you don’t have to patch and paint your walls

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B01NB1OB0I |
| Additional Features | Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable |
| Backlight | Yes |
| Best Sellers Rank | #1,612 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #6 in Home Programmable Thermostats |
| Brand | Emerson |
| Brand Name | Emerson |
| Color | White |
| Connectivity Protocol | Wi-Fi |
| Connectivity Technology | Wi-Fi |
| Control Method | Voice |
| Control Type | Button Control |
| Controller Type | Amazon Alexa, Google Assistant, SmartThings, Vera |
| Customer Reviews | 4.4 out of 5 stars 22,661 Reviews |
| Display Type | LED |
| Finish Types | Glossy |
| Global Trade Identification Number | 00786710554827 |
| Included Components | Thermostat, free mobile app, 2 AA batteries, mounting hardware, wire stickers, installation guide, welcome guide with Sensi code, warranty booklet |
| Item Dimensions D x W x H | 1"D x 5.88"W x 3.75"H |
| Item Type Name | , Works with Alexa, Energy Star Certified |
| Item Weight | 0.85 Pounds |
| Manufacturer | Copeland |
| Manufacturer Part Number | ST55 |
| Manufacturer Warranty Description | 3 years. |
| Material Type | Plastic |
| Model Name | Wi-Fi Thermostat for Smart Home, DIY Version |
| Model Number | ST55 |
| Mounting Type | Wall Mount |
| Number of Batteries | 2 AA batteries required. (included) |
| Power Source | Corded Electric |
| Product Dimensions | 1"D x 5.88"W x 3.75"H |
| Product Style | DIY |
| Screen Size | 5 Inches |
| Shape | Rectangular |
| Smart Home Compatibility | Smart Home Compatible |
| Special Feature | 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 |
| UPC | 786710554827 |
| Unit Count | 1.0 Count |
| Voltage | 24 Volts (AC) |

## Product Details

- **Brand:** Emerson
- **Controller Type:** Amazon Alexa, Google Assistant, SmartThings, Vera
- **Model Name:** Wi-Fi Thermostat for Smart Home, DIY Version
- **Product Dimensions:** 1"D x 5.88"W x 3.75"H
- **Special Feature:** Data Privacy, Easy DIY Install, Energy Savings, Filter Indicator, Programmable

## Images

![Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 - Image 1](https://m.media-amazon.com/images/I/61Rl-IZR--L.jpg)
![Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 - Image 2](https://m.media-amazon.com/images/I/61eYIzj13TL.jpg)
![Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 - Image 3](https://m.media-amazon.com/images/I/61VwfOjqYjL.jpg)
![Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 - Image 4](https://m.media-amazon.com/images/I/512MPfJJUJL.jpg)
![Emerson Sensi Wi-Fi Smart Thermostat for Smart Home, DIY, Works With Alexa, Energy Star Certified, ST55 - Image 5](https://m.media-amazon.com/images/I/71oW2hSiPiL.jpg)

## Available Options

This product comes in different **Pattern, Style** options.

## Questions & Answers

**Q: Can you create a fan schedule?  I’d like the fan to always run from 10pm until 6am.**
A: Updated Answer:
THANK YOU to Albert who pointed out below that the fan can be controlled through SmartThings! It was annoying to have to set up another app and service to do this, but it is a workaround to get around Sensi's frustrating limitation. SmartThings allows you to set the fan to Auto, On, or Circulate (but not the percentage of time to circulate) and automate that on any schedule you want. Unfortunately, Alexa and Google still don't allow you to control the fan at all, even though Sensi's API apparently allows it.

Original Answer from June 6, 2020:
No, you can't do a schedule like if you want it to run all the time during the night. Also, you can't control the fan from Alexa to schedule it that way. Very annoying and unreasonable that they wouldn't add that option since you can turn it on manually from the app. They do have the auto-circulate feature, but that's not the same.

**Q: Is it smart enough to decide whether to run the heater or cooler to keep the temperature fixed?**
A: In spite of the snarky answer above that says that's what a thermostat does, it should be noted that a thermostat doesn't just so that unless it is a feature of the thermostat.

A thermostat is for comparing existing ambient temperature to programmed temperature. On a furnace, if the temperature exceeds the programmed temp, the furnace simply will not run. THAT is what a thermostat does. UNLESS there is the ability to set said thermostat to automatically adjust the temp to the programmed temp.

**Q: Can you program just the fan mode?**
A: As pointed out on a similar question, the Sensi app does not allow scheduling of the fan mode, but you can do it with a 3rd party integration to the SmartThings app. Unfortunately, Alexa and Google don't have the option to control the fan either, but the SmartThings workaround was good enough for me to set our fan to run automatically at night and turn off in the morning.

**Q: What if i have a C wire?**
A: The "C-wire" is the second wire for 24VAC which is used to power advanced thermostats. Older thermostats were just a mercury switch and didn't have a need for additional power supply. Most newer systems are using 5-conductor thermostat wire.. Think of it as the plus side of a DC circuit/battery (but it is AC[thermostats have a rectifier to convert the AC to DC for their use]). Use it and the "common-wire" to supply 24VAC to the thermostat and zone valves/zone dampers. Without it, the thermostat runs on battery all the time and will quickly run down with WiFi.  Add a zone controller like a Honeywell HZ311 which has full modern voltages output; i.e., c-wire with 24VAC. This control requires a 24VAC transformer and daisy chains the 24VAC to thermostats and works on older systems since it provides its own c-wire output to advanced thermostats.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Fairly east to set up, works well with Google Home
*by J***. on December 11, 2020*

(Long, but I hope worth the read) Overall, I am extremely happy with the Emerson Sensi smart thermostat. For me it was a pretty easy project, but it is important that you know what type of cooling/heating system you have prior to attempting the installation. Although the basic installation is made very simple using the Sensi app, there were some very important things not covered. I suggest you check out how to configure your Sensi on their site (Configuring Thermostat | Sensi US (emerson.com)). I’m a pretty good DIYer, but have very little experience with AC/heating systems. I was 99% sure I had a heat pump setup, but I called a local AC technician I know to confirm and am glad I did. Having installed a few smart thermostats, to include this one, he not only confirmed I had a heat pump, he also informed me I would have to go into the system settings on the thermostat and change the outside setting from ‘AC1’ to ‘HP1’. This was confirmed when I checked out the Sensi website. Armed with this information, installation went without a hitch and I was up and running in no time. Pros: - Easy to install, if you have a little DIY experience, all the information needed concerning your AC/Heating system and gather the additional information before starting. - Very easy to connect to WiFi and integrate with Google Home. Connected to my WiFi with in seconds following the instructions; when I opened my Google Home app, there was an icon to add Sensi, clicked on it and moved the thermostat to the appropriate room. I have not experienced any drop-offs or loss of the WiFi, even when I turned off my WiFi for a few hours, removed the batters or installed old, weak batteries as tests; in every case, the thermostat remained connected or automatically connected right back up in seconds with no need to go through the WiFi setup operations again. - The Sensi app, in addition to walking you through the installation, allows you to set up various cooling/heating programs to run automatically, as well as change other settings. Once added to Google Home, you can switch programs (cool, heat, auto), turn it on/off and set the temp. You can also use voice commands through Google to do this as well. - The ability to adjust the thermostat to compensate for temperature offsets. In my case, where my thermostat is located the temp registers about 3 degrees off from what it is in our master bedroom or living room. I simply adjusted the offset in the Sensi app to compensate for this and now our bedroom and living room remain closer to the set temp then they have in the past. - It can be operated manually by those less tech savvy. The controls on the face plate look and operate like those on our old ‘conventional’ one. I also like that you can lock out the manual operation from the app so that no one else can mess with the settings; like during the holidays when you have family members over who feel they can change the settings without asking .. lol. - Being able to adjust the system cycling rates. There are three settings (short, medium, and long) that can be set independently for heat, heat aux and cooling. I don’t mind having my temps vary a degree before the system cycles back on, so I have all mine set to long; during the summer, I may switch cooling to short to see how much of a difference it makes. Con: I only have one and it is the reason for my 4 rating. The instructions, at least those in the box, should include information on the additional settings that may need to be needed depending on the AC/heating system you have. At a minimum, they should inform you that you may need to make additional setting changes and where to find the instructions online.

### ⭐⭐⭐⭐⭐ Works with boilers and does NOT require a C-wire
*by M***S on June 19, 2022*

I moved to the East coast last December. We have a six-zone boiler heating system with baseboard heaters throughout 4,200 sq. ft., on three floors (not bragging, just trying to give an idea of the size and complexity of the system). With six old-school manual thermostats spread throughout the house, it was nearly impossible to evenly regulate the heat during the cold winter, so some rooms were very cold and others too warm. I found myself constantly going up and down stairs to monitor temperatures and make sure I wasn't wasting heat or keeping areas too cold that would affect other zones. My boiler was installed in 2007, so it isn't very old and it's very efficient. However, it's a two-wire system with no C-wire, so the fact that 99.9% of "smart" thermostats on the market require a C-wire to operate was very frustrating. I stumbled across the Emerson ST55 and saw in the description that it could work either with or without a C-wire, so I called Emerson tech support to make sure before I plunked down hundreds of dollars on six thermostats that might not work. Tech support confirmed my fears that it would not work without a C-wire despite the Amazon description, so I kept hunting. Fortunately I found a YouTube review of the ST55 and the owner said he had been successfully using it with the same kind of two-wire system that I have for over two years. So I figured I'd buy one and see if it worked. Worst case, I'd send it back for a refund. The instructions inside the box clearly state that it will not work without a C-wire, but I ignored them and kept going. With only two wires it was a breeze to install. I put in the batteries, snapped it into the wall plate, downloaded the app, created an account and was ready for testing in about 15 minutes. I'm not sure if it's just my system or all boilers, but I didn't realize it doesn't turn on instantly when the thermostat temperature is raised above the existing temperature. So when I first tested it, I was bummed that it didn't work. But as I walked downstairs to the boiler, it was running! So I did some more testing, and found that there's about a 20-25 second delay between increasing the temp and the boiler kicking in. Granted it's only been a couple months since I got it, but I've played with it plenty and it's working great. Instead of a C-wire, the thermostat is powered by two AA batteries. The guy in the video said he's been using the same regular alkaline batteries for two years and they're still at 90% charge capacity, which is awesome. But I figure that even if I have to replace batteries every year, 12 AA batteries is a helluva lot cheaper than paying an electrician to rewire all six zones! On top of the six heat zones, I also have two central AC units. Thankfully those have C-wires, but I'm going to replace those thermostats with the Emerson ST55 also so that I'll have full control of all heating and cooling from one simple-to-use app. With any luck it'll go on sale on Prime Day so that I can save some money! :-) I can't speak to the Alexa integration as I don't use that functionality. But plenty of other reviewers have said it works fine. I appreciate Emerson's thoughtfulness in adding a built-in level to the back plate. I'm a stickler about things being mounted straight, so it was nice to not have to break out a level to make sure I didn't mount it crooked. As for aesthetics, the ST55 is nice. It's not too large to look obnoxious, but it has a good-sized display. And I'm not sure if it's just because I'm running it on battery, but the back light doesn't stay on constantly, so it doesn't light up a dark room at night (not too important in common areas, but important if you've got a thermostat in a bedroom). So, to make a long story short, don't believe Emerson. This thing really does work on a two-wire boiler heat system with no need for a C-wire!

### ⭐⭐⭐⭐⭐ No C-Wire? No Problem! No Monthly Fee
*by J***S on March 27, 2026*

~ Easy Install: No C-wire/power line needed. The phone-guided setup is excellent, which is good because there is very little paper documentation. ~ Performance: Has worked flawlessly for months. ~ No Hidden Costs: I love that there are no monthly fees for app access. ~ Remote Access: Being able to bump up the heat from my phone before I get home from a trip is a huge plus. Highly recommended for a simple, cost-effective DIY upgrade.

## Frequently Bought Together

- Sensi Smart Thermostat, 100 Years Of Expertise, Wi-Fi, Data Privacy, Programmable, Easy DIY Install, Works With Alexa, Energy Star Certified, Mobile App, ST55
- Emerson F61-2663 Wall Plate for Sensi Wi-Fi Programmable Thermostat, White
- CAMGJORT F61-2663 Wall Plate for Sen si Wi-Fi Programmable Thermostat,Hand Control, White (1)

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*Product available on Desertcart United States of America*
*Store origin: US*
*Last updated: 2026-05-19*