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.

How do I know if I have a wired or a battery-powered smoke alarm?

Before you buy Nest Protect, you'll want to check if the wired or battery-powered model will work for you. If you're not sure what you currently have in your home, you'll need to look at your current smoke alarms and see if they have wires - and if those wires are supplying power.

One indication that you have a wired smoke alarm is a solid or flashing green LED on the device. This is usually used on wired alarms to indicate that it has power.

However, if there’s no green LED, it doesn’t necessarily mean your smoke alarm is battery powered. The fastest way to be sure what type of alarm you have is to take it off the wall or ceiling.

If there are no wires coming out of the wall or ceiling

If the smoke alarm simply twists off the baseplate and there are no connecting wires, then you have a battery-powered device.

If there are wires coming out of the wall or ceiling

Wired smoke alarms typically have two or three wires coming out of the wall or ceiling that feed into a connector for the alarm.

Two of these wires — typically black and white — supply the power to the smoke alarm.

Important note: If those wires also connect your existing alarm to your home security system, Nest Protect won’t work with the security system. Nest Protect interconnects to other Nest Protects wirelessly, but not through a security panel.