The bottom line: With so many extra goodies, like a built-in Amazon Alexa, a power extender, and a room sensor to monitor the ambient temperature, it’s hard not to be tempted by the ecobee4 thermostat, especially if your thermostat doesn't have a C-wire.
Amazon Alexa: Yes, with the “ecobee” or “SmartThings” skill enabled
Google Home: Yes, through the Wink (Android/iOS) app
Apple HomeKit/Siri: Yes
Setup/Installation: One of the biggest selling points about the ecobee4 is that it comes with a power extender, which eliminates the need for a C-wire. If you do not already have a C wire and you don’t want to shell out for a professional to add one, this is your best bet for upgrading to a smart thermostat. The power extender acts as a middleman between the HVAC system and the thermostat, so to use it, you’ll still need to be able to pull wires from your heating/cooling system, plug them into the power extender, and run those wires behind the wall to the back of the thermostat.
The setup instructions are extremely thorough. They are accompanied by videos and diagrams, including a really useful part about verifying that the HVAC system has been shut down safely. For the ecobee4 to work, your R wire (whether it’s an R, Rc, or Rh wire) must be placed in the Rc terminal.
We also like that a separate temperature sensor is included with the ecobee4; it can be mounted anywhere, so your ecobee4 can tell how cold the bedroom is, even if it's installed in the hallway.
Amazon Alexa has also been physically integrated with the ecobee4. This means that you can control the ecobee4 thermostat vocally without purchasing or using an additional Amazon Alexa unit. On the other hand, it only worked when we were in shouting distance of the thermostat itself. It is Apple Homekit compatible, and like the Sensi thermostats, the ecobee4 works with Google Home via the third-party Wink app.
Usability: With a full touchscreen on the thermostat interface, it’s easy to make temperature changes at the thermostat. However, we found that the ecobee app is a bit too streamlined. It’s a little bit tougher to navigate because the minimal labeling makes it hard to find exactly what you want. In order to change the temperature in the app, you have to drag the temperature down like a scroll bar, and with no number labels, it is easy to over- or undershoot the desired temperature.
Geofencing works beautifully. It’s easy to adjust the size of the “home” zone, and you are pinged with notifications when you enter or leave the home zone. On the other hand, the scheduling function is not as precise as some other apps, and only lets you schedule different "home", "away", and "sleep" events, where any two events of the same kind (i.e. two "home" events) cannot have different temperature settings.
One thing we did really like about the app is its easy-to-read status screen, which tells you whether the geofencing home/away state, the schedule, or a manual override is currently running; to change to a new command, we were able to click the x in the corner of the status window and it reverted to the previous command.
In our experience, vocal commands routed through Amazon Alexa (be sure to stand close to the thermostat if you’re using the built-in Alexa), Google Home, and Siri were executed quickly and correctly. The same was true for remote commands done over a 4G network.
Looks: The ecobee4 is very noticeable, and looks like it belongs on a spaceship. Between its black faceplate, curved edges, and Amazon Alexa speaker, we kept wanting to order it around like it was our own personal AI: “Hey ecobee4, do my laundry.” The ecobee4 also comes with an optional large white backplate in case the profile of the ecobee4 is smaller than your previous thermostat, and unsightly paint lines would be visible otherwise.
What users are saying: The ecobee4 has many happy customers, with the highlights including the external Alexa speaker, easy to follow installation instructions, and the power extender that replaces a C-wire. The biggest complaint is that the Alexa integration has limited functionality compared to a separate Alexa unit.