There have been two generations of the Nest Learning Thermostat. The first was first announced on October 25, 2011. The 2nd generation Nest Learning Thermostat was first announced on October 2, 2012.

The 2nd generation Nest Learning Thermostat has more wire connectors for increased compatibility and an updated design, but both generations of the Nest Learning Thermostat run the same version of software. If your heating and cooling system was compatible with the 1st generation Nest Learning Thermostat, you won’t see a difference in terms of features or performance with the 2nd generation Nest.

Here are two ways to tell the difference between the 1st and 2nd generation Nest:

1) Differences in the Nest display

The 1st generation Nest Learning Thermostat has a grille at the bottom of the display. The 2nd generation Nest Learning Thermostat has temperature, humidity, activity, and light sensors hidden behind an opaque, black sensor window.

The ring is also different. On the 1st generation Nest Learning Thermostat, the ring is just the front ½ inch of the display. The 2nd generation Nest Learning Thermostat’s display is entirely surrounded by a single stainless steel ring.

2) Differences in the Nest base

The 2nd generation Nest Learning Thermostat is compatible with more heating and cooling systems than the 1st generation because it has two more connectors.