Thermostat guide
ecobee Smart Thermostat Premium wiring guide
Room sensor, air-quality monitor and built-in Alexa. Handles 2 heat / 2 cool stages, heat pumps with 2 aux stages, and humidifiers via ACC terminals. Power Extender Kit included.
What it supports
| Conventional systems | Up to 2 heat / 2 cool stages |
|---|---|
| Heat pumps | 2 compressor stages, 2 aux stages, no E terminal |
| Dual fuel | Supported |
| Dual transformer (Rh/Rc) | Supported |
| Power / C wire | Needs a C wire, or the included Power Extender Kit with 4 wires (R, W, Y, G). |
| Line voltage / millivolt | Not compatible |
Where your old wires go
| Old terminal | ecobee Premium terminal |
|---|---|
| R (single transformer) | Rc |
| Rh + Rc (dual transformer) | Rh |
| C (common) | C |
| W / W1 (heat) | W1 |
| W2 (2nd-stage heat) | W2 |
| AUX / W2 on a heat pump | W1 |
| E (emergency heat) | None |
| Y / Y1 (cool) | Y1 |
| Y2 (2nd-stage cool) | Y2 |
| G (fan) | G |
| O, B or O/B (reversing valve) | O/B |
| K (wire saver) | None |
| 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 ecobee Premium
ecobee thermostats need constant power. If you don’t have a C wire, the included Power Extender Kit (PEK) goes in at the furnace and uses your existing 4 wires (R, W, Y, G). Because it needs those 4 wires, the PEK doesn’t help a 2- or 3-wire system.
ecobee has no E terminal: emergency heat is a mode that uses the aux heat terminals. On heat pumps, backup heat goes on W1 (and W2 for a second stage). The ACC+ / ACC− terminals run a humidifier, dehumidifier or ventilator, which the Enhanced model can’t.
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ecobee Premium with common wiring setups
| Setup | Verdict |
|---|---|
| 2-Wire Thermostat (Heat Only) | Works with an adapter |
| 3-Wire Thermostat (Heat + Fan, No C Wire) | Works with an adapter |
| 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 | Works: direct swap |
| 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 | Pro install recommended |
| K Terminal Wiring (Honeywell Wire Saver) | Pro install recommended |