Nest Support

Questions about Nest Learning Thermostat or Nest Protect: Smoke + CO alarm? We've got answers, videos, and plenty of resources to help you out.

Power Specifications for the Nest Learning Thermostat

The Nest Thermostat is designed to be compatible with low voltage systems. The Nest Thermostat is not compatible with millivolt or high voltage (line voltage) systems.

The Nest Learning Thermostat works with low voltage systems within a range of 20 - 30V AC. Each wire that the Nest Thermostat uses to draw power (C, Y1, and/or W1, depending on the system) must comply with these voltage requirements.

Power Wire Connections Positive Power Terminal Negative Power Terminal Voltage Requirement
C Wire Connected Rc
(Rh if Rc is not connected)
C 20 - 30V AC*
Y1 Wire Connected, C Wire Not Connected Rc
(Rh if Rc is not connected)
Y1 20 - 30V AC*
W1 Wire Connected, C & Y1 Wire Not Connected Rc
(Rh if Rc is not connected)
W1 20 - 30V AC*

Some HVAC systems have high resistance in series with the Y1 and/or W1 power lines. This can prevent the voltage requirement from being met during Nest Thermostat operation. In order for the Nest Thermostat to be compatible with these systems, a common (C) wire is required.

*The Nest Thermostat's Technical Info screen measures Voc and Vin values for voltage it's measuring on your wires. These values represent the peak of an AC sine wave. Voc is the value to pay attention to when determining if your system is within the support range. To translate these values to the same scale as the specification above, divide the Voc value by 1.414.