When I lived in Japan I had a co-worker look up from his phone one day to an alert that his unoccupied house in Arizona was too hot. He called a family member and confirmed that there was an HVAC problem. It was at that moment I understood the importance of a smart Thermostat.
As soon as I moved back to the US in around 2015 I had a home built and I immediately installed a 2nd Generation Nest. Recently I bought a new home and installed a 3rd Generation Nest Learning Thermostat ($249 but now reduced to $199) downstairs and a Nest Thermostat (4th Generation) ($129) upstairs. A few weeks into the new home we opted to install a new upstairs A/C unit which came with a 3rd Generation Nest Learning Thermostat which I had them go ahead and install.
You might think a 4th generation product would be “better” than a 3rd generation product however I don’t really find this to be the case. The 4th gen only works with the Google Home app whereas the 3rd gen works with the Nest app, the Google Home app, and a web browser. Also the 3rd gen integrates with Alexa. To voice command the 4th gen you need a Google Nest Hub. Speaking of Alexa integration, when I added the 2nd Nest Learning Thermostat Alexa could not find it. I had to disable the Google Nest skill in Alexa and re-enable it before the Alexa voice commands would work on both thermostats. There is something very cool about just saying “Alexa, Set Hallway temperature to 74” in the middle of the night without having to get up.
So to me the 3rd gen Nest Learning thermostat has way more flexibility. Also the HVAC installers told me that they did NOT like the 4th gen at all. Let me preach on it…….