On a conventional furnace or boiler, W / W1 is the first stage of heat. It is typically white, but again, go by the letter.
On a heat pump, the compressor provides heat through Y, and a W wire usually runs the backup auxiliary electric heat strips. That is why the same letter can land on a different terminal depending on your system, and why our tool asks whether you have a heat pump.
Wires: R, W, Y, G, C · open in the tool
| Thermostat | W goes to | Whole setup |
|---|---|---|
| Nest Learning (4th gen) | W | Works: direct swap |
| ecobee Premium | W1 | Works: direct swap |
| ecobee Enhanced | W1 | Works: direct swap |
| Honeywell T9 | W | Works: direct swap |
| Amazon Smart Thermostat | W | Works: direct swap |
Wires: R, C, Y, G, O/B, W · open in the tool
| Thermostat | W goes to | Whole setup |
|---|---|---|
| Nest Learning (4th gen) | W | Works: direct swap |
| ecobee Premium | W1 | Works: direct swap |
| ecobee Enhanced | W1 | Works: direct swap |
| Honeywell T9 | W2 / Aux | Works: direct swap |
| Amazon Smart Thermostat | W | Works: direct swap |
Wire My Thermostat