What really works in Home Assistant without internet?
Home Assistant runs on hardware in your home and can control local devices without an internet connection. That does not mean every part of a smart home retains full functionality.
A real system usually combines local devices, cloud services and network infrastructure. A better question than “does Home Assistant work without internet?” is “what does each function in my home depend on?”.
Loss of internet, router failure and Home Assistant failure are different events
- Internet or WAN outage: the provider connection is down, while the router, LAN, Wi-Fi and Home Assistant can keep working.
- Router or local network failure: devices may lose Wi-Fi, IP addressing or their communication path to Home Assistant even though the server is running.
- Home Assistant host failure: device networks may still exist, but automations executed by Home Assistant will not run.
These failures have different consequences. Saying “the internet is down” often attributes too many problems to the WAN connection.
The router can keep the home network running after WAN is lost
A router usually connects devices on the LAN, provides Wi-Fi and assigns addresses through DHCP. When only internet access is lost, these functions can continue. Home Assistant, a phone and a local Wi-Fi device can remain on the same network and communicate.
Router failure is more serious. Wi-Fi may disappear, while wired or wireless devices may lose contact with one another. The impact depends on separate access points, switches and whether a specific function needs the router.
DHCP reservations or another predictable addressing method help stable communication and diagnosis of key devices. They do not protect against failure of the router itself or loss of power to the network infrastructure.
Local and Cloud describe the route, Polling and Push the update method
- Local Polling: Home Assistant asks a device directly on the local network for its current state.
- Local Push: a local device or hub sends a state change directly to Home Assistant.
- Cloud Polling: Home Assistant periodically asks a vendor service over the internet.
- Cloud Push: a change reaches Home Assistant through a vendor cloud service.
Polling does not mean cloud, and Push does not mean local. Resilience mainly depends on whether the communication route is local and whether every component along it is available.
Local devices and automations can continue normally
With Home Assistant and local infrastructure running, locally coordinated Zigbee devices, local Wi-Fi devices and local sensors can work without internet. This can include lights, covers, heating, scenes and group control.
A local automation can receive motion from a Zigbee sensor and switch on a locally controlled light. It needs no WAN if none of its triggers, conditions or targets use an unavailable cloud service.
The label “Wi-Fi” does not prove local control. A device can be connected to the home wireless network while accepting commands only through its vendor's server.
Cloud services, remote access and external data need internet
Cloud Polling and Cloud Push integrations, cloud-only devices, weather forecasts, energy prices and other external data can become unavailable. Internet-based remote access also stops, although the dashboard may still open locally.
Some voice services need the cloud. A local voice pipeline can work without it when every component runs at home. The actual configuration matters more than the assistant's name.
An automation may be stored and executed locally but still fail when its condition uses a cloud entity or its target is available only through the internet. Design for unavailable states instead of treating the last known value as current.
Internet is down, but the router and Home Assistant are running
A phone on home Wi-Fi can still open the local Home Assistant dashboard. A Zigbee motion sensor reports movement, the automation runs on the server and a locally controlled light switches on as usual.
At the same time, a cloud-only plug may be unavailable, the weather forecast will not refresh and access from outside the home will stop. One outage therefore produces different results within the same system.
The router has stopped working
Zigbee is a separate radio network and may continue to exist. If its coordinator is attached directly to the running Home Assistant host, ZHA communication with Zigbee devices can remain available. A network coordinator, Zigbee2MQTT on another computer or other LAN-connected components may no longer have a path to Home Assistant.
Wi-Fi devices usually lose connectivity when the router is also the access point. With separate access points and switches, part of the LAN may remain active, but the outcome depends on topology, DHCP, addressing and communication methods. There is no single rule for every home.
Home Assistant has stopped working
Devices may remain in their networks, but logic implemented in Home Assistant is unavailable. A sensor may still transmit an event on the Zigbee network, yet a Home Assistant automation will not react.
A physical control on a light, thermostat or cover can still work if it controls the device independently. A direct Zigbee binding between compatible controls and lights can also bypass Home Assistant. Behaviour depends on system design and device capabilities, so essential control should not rely exclusively on one controller.
How can you assess your own smart home's resilience?
- Check each integration's IoT class and connection method in its documentation.
- Identify automations using cloud entities, external data or coordinators reached through the LAN.
- Decide which functions must still work through a physical control when Home Assistant is stopped.
- Run a controlled WAN outage test without disconnecting the router or local network.
- Use predictable addresses for key devices and keep clear network documentation.
Full redundancy is a separate project. Even a simple dependency map shows whether a critical light, heating system or cover relies on the cloud or a single infrastructure component.
Local Home Assistant does not automatically make the entire home local
Resilience depends on every device's communication method, integration type, router and LAN availability, the Home Assistant host and the design of automations.
A good system does not promise that every function survives every failure. It makes dependencies clear, keeps essential controls local and defines safe behaviour when the cloud or controller is unavailable.
Would you like to know what in your system depends on the internet?
I can analyse devices, integrations, network paths and automations, identify cloud dependencies and organise the system so that essential functions are more resilient to failures.
Request a Home Assistant resilience review.We will first identify devices, critical functions and current dependencies. → click here