I bought the T6 thermostat to control my geothermal system. It is generally ok but there are a couple of things i wish were better. 1. Other, cheaper, Honeywell thermostats will show you right on the screen that aux heat is being used. This one only shows heating and you have to dig in the menus to determine if aux heat is on. The App also doesn't share that information. For a system with electric backup it is very expensive and the owner wants to know. 2. I have had an issue where my compressor kicked off due to poor pressure and it ran only on backup. The thermostat and the app give no indication of a compressor failure. Not good.
I got two of these installed because my previous thermostats that were a popular brand weren’t the right fit for my air handlers. What this thermostat lacks is a heat/cool option. So if it’s set to cool 72 degrees and overnight the temperature drops to 68 degrees it will not automatically warm it up to 72. Same thing in reverse for heat setting. A heat/cool setting would automatically hold the temperature for you. So yeah it’s WiFi enabled, but I wouldn’t say smart. It cost a fortune too.
We've only had the thermostat for 1 month, but so far it is working well. However, it took us 3 weeks and a call to customer service to determine why it was turning on the oil burner hours before the WAKE time setting. It turned out to be what we think is a design flaw. The thermostat is designed to start the heating system before the time we set as WAKE time so that it would reach the desired temperature at the WAKE time, unlike any other thermostat we have ever had. However, the temperature was reaching the desired temperature hours earlier and the thermostat was keeping it at that temperature for 2+ hours until we reached the actually morning WAKE time. We actually had our oil burner tech come to the house 3 times and he changed the thermostat out twice before we called Honeywell tech support. The tech person finally figured out what the problem was and was able to flip a switch remotely that fixed the problem. I hope Honeywell will change this design in future models.