Smart home: devices, protocols and local control

It depends on the radio your devices use. Wi-Fi devices talk to your router directly, so a home built only from Wi-Fi plugs and bulbs needs no hub at all; each device joins the network on its own and is controlled through the vendor's app or a local controller. Zigbee and Z-Wave devices cannot join a Wi-Fi network, because they use a different radio, so they need a coordinator: a small box or USB stick that speaks their protocol and bridges it to the rest of the house. Thread devices need a border router for the same reason, although that role is often built into a speaker, a display or a newer Wi-Fi access point.

The practical answer is that most homes end up with one hub whether they planned to or not. A single coordinator that speaks Zigbee and Thread, running a local controller, is the tidiest arrangement: every device joins it, automations run on it, and the phone app becomes a remote rather than the brain. The article on local-only smart homes walks through that setup.

Only if the control path stays inside the house. A device that reports to a vendor cloud and receives commands back from it stops responding the moment the internet link drops, even though the device and your phone are a few meters apart on the same network. A device controlled by a local hub or a local controller keeps working, because nothing in the chain leaves the building.

The way to find out is to test it: turn off the router's internet connection, leave the local network up, and try each device from the app or a switch. Anything that fails is cloud-dependent. You can then decide whether to replace it, to keep it for non-critical jobs, or to move its automations onto a local controller that talks to the device directly. Lights, heating and door locks are the things people most regret leaving on a cloud path.

Pick one low-power mesh protocol for the bulk of your sensors and switches, and accept Wi-Fi for the handful of devices that genuinely need bandwidth, such as cameras and speakers. Zigbee has the widest choice of inexpensive devices and works well with a single coordinator; Z-Wave has a stricter certification and a licensed band with less interference, at a higher price per device; Thread is the newest of the three and is the radio Matter prefers for battery devices.

The comparison article goes through range, interference and hub requirements in detail. Whichever you choose, the more useful decision is to run everything through one local controller, so that a device's protocol becomes an implementation detail rather than a lock-in. If you are starting from nothing today, a coordinator that speaks both Zigbee and Thread keeps both doors open.