Thermostat guide
Amazon Smart Thermostat wiring guide
The budget pick, set up through Alexa. Simple systems only: single-stage heat/cool or a single-stage heat pump. Needs a C wire or Amazon’s C-wire adapter.
What it supports
| Conventional systems | Up to 1 heat / 1 cool stage |
|---|---|
| Heat pumps | 1 compressor stage, 1 aux stage, no E terminal |
| Dual fuel | Not supported |
| Dual transformer (Rh/Rc) | Not supported |
| Power / C wire | Needs a C wire, or Amazon’s C-wire power adapter with 4 wires (G to C, Y to K). |
| Line voltage / millivolt | Not compatible |
Where your old wires go
| Old terminal | Amazon Smart Thermostat terminal |
|---|---|
| R (single transformer) | R |
| Rh + Rc (dual transformer) | None |
| C (common) | C |
| W / W1 (heat) | W |
| W2 (2nd-stage heat) | None |
| AUX / W2 on a heat pump | W |
| E (emergency heat) | None |
| Y / Y1 (cool) | Y |
| Y2 (2nd-stage cool) | None |
| G (fan) | G |
| O, B or O/B (reversing valve) | O/B |
| K (wire saver) | K |
| L / L/A (service light) | None |
B, X and K depend on your system. Use the tool to check. Confirm with the official guide.
What’s different about wiring the Amazon Smart Thermostat
The Amazon Smart Thermostat is built for simple systems: one heat stage and one cool stage, or a single-stage heat pump with one aux stage. It doesn’t support second stages, dual transformers (Rh/Rc) or dual fuel. If your old thermostat has wires on W2, Y2 or both Rh and Rc, choose a different model.
It needs a C wire. Without one, Amazon’s C-wire power adapter goes in at the furnace: the wire that was on G moves to C, and the Y wire moves to K, which carries both cooling and fan.
Check the Amazon Smart Thermostat price on Amazon
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Amazon Smart Thermostat with common wiring setups
| Setup | Verdict |
|---|---|
| 2-Wire Thermostat (Heat Only) | Not compatible |
| 3-Wire Thermostat (Heat + Fan, No C Wire) | Not compatible |
| 4-Wire Thermostat Wiring (No C Wire) | Works with an adapter |
| 5-Wire Thermostat Wiring (With C Wire) | Works: direct swap |
| Cooling-Only Thermostat Wiring (AC + Fan) | Works: direct swap |
| 2-Stage Heat & 2-Stage Cool Thermostat Wiring | Not compatible |
| Heat Pump Thermostat Wiring (5 Wires, No C Wire) | Works with an adapter |
| Heat Pump Thermostat Wiring (6 Wires With C Wire) | Works: direct swap |
| Heat Pump Wiring With AUX and E (Emergency Heat) | Probably works: verify first |
| Heat Pump With a B Wire (Rheem / Ruud Style) | Works: direct swap |
| B Wire as Common (Trane / American Standard Style) | Works: direct swap |
| Rh and Rc Wires (Dual Transformer) Thermostat Wiring | Not compatible |
| K Terminal Wiring (Honeywell Wire Saver) | Works: direct swap |