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How can I tell which Nest Learning Thermostat I have?

A guide to help identify which generation of the Nest Learning Thermostat you have.

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

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

1) Differences in the Nest Thermostat display

The 1st generation Nest Thermostat has a grille at the bottom of the display. The 2nd generation Nest 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 Thermostat, the ring is just the front ½ inch of the display. The 2nd generation Nest Thermostat’s display is entirely surrounded by a single stainless steel ring.

2) Differences in the Nest Thermostat base

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

2nd generation
Nest Learning Thermostat

1st generation
Nest Learning Thermostat

It can control:

  • Heating: 1, 2 and 3 stages (W1, W2, W3)
  • Cooling: 1 and 2 stage (Y1, Y2)
  • Heat pump: with auxiliary and emergency heat (O/B, AUX, E)
  • Humidifier or dehumidifier (HUM, DEHUM)
  • Fan (G)
  • Power (C, Rh, Rc)

The Nest Thermostat's connector can accept only one of these wires:

  • W3, E, HUM or DEHUM

It can control:

  • Heating: 1 and 2 stages (W1, W2)
  • Cooling: 1 stage (Y1)
  • Heat pump: with auxiliary heat (O/B, AUX)
  • Fan (G)
  • Power (C, Rh, Rc)