Sensi Smart Thermostat, 100 Years Of Expertise, Wi-Fi, Data Privacy, Programmable, Easy DIY Install, Works With Alexa, Energy Star Certified, Mobile App, ST55

Easy setup and works great with lots of features
The Sensi Smart Thermostat is very simple to use and setup. I like the crisp display and easy menus but the beauty of this device is the wifi and app control. I was able to connect using my home network and create a schedule that fits my needs. I can remotely control the thermostat while I’m away so if I want to bump the heat up before I arrive home I can simply do it via the Sensi app. There is no need to setup an account unless you want to control multiple thermostats then you have plenty of choices by the looks of it. I like the ease of use and the clear display and simple controls to manually adjust it if I want to. I highly recommend this if you’re looking for wireless capabilities and simple setup. I was able to install it and set it up in 45 minutes and its working great.

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 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!

A Sensi-ble thermostat
It’s a pretty good basic wifi thermostat.Plus: Easy to install, easy to use, easy to set up. Can install without a C-wire as it is battery powered. App is easy to use, and basic, but functional.Cons: Can’t see it at night. Once you push a button, the back-light comes on, but sometimes you just want to check what the setting is and not change a setting. But when you push a button you probably change a setting, and then you have to figure out what the setting was at before you changed it.