Smart home during a power outage: preparing your system

Home Assistant runs on hardware in your home and can keep working when the internet connection goes down. Devices using local protocols such as Zigbee, Z-Wave, Matter, Thread, or ESPHome can continue to communicate with the controller and run automations without cloud access.

Local operation does not mean operation without electricity. If the controller, router, coordinator, or devices lose power, local communication stops too. A cloud-based device may become unavailable even if Home Assistant and Wi-Fi are running. Plan for both situations separately.

List what should remain available during an outage, such as local lighting, leak alerts, or heating controls. For each item, check its dependencies: the Home Assistant controller, router, access point, Zigbee coordinator, modem, and end device.

You do not need backup power for the whole home. Start with equipment required for an essential function. Compare device power use and desired runtime with the UPS specifications, then check actual runtime in practice. Have a qualified electrician handle fixed wiring.

For important functions, prefer devices and automations that work locally without requiring a connection to the vendor’s server. Keep a standard switch or another clear manual control in case the controller or network is unavailable.

Do not make a phone app the only way to access critical functions. Remote access is separate: Home Assistant Cloud and other remote-access methods need internet and powered equipment at home. Check what remains available locally.

Safely test the system by temporarily disconnecting the internet while keeping power on. Confirm that the local automations you need still work. Separately test behavior after a brief power interruption: does the controller restart, do devices return to the expected state, and do any unwanted routines run?

Decide what to do manually if backup power runs out. If an automation controls heating, a gate, or other important equipment, do not make it the only way to operate it. A simple plan and tested manual controls are more useful than an untested routine.