KNX
The wired European building-automation standard with a 30-year track record.
KNX is what "smart home" means in European new builds and commercial buildings: a wired bus standard, run by the KNX Association since 1999 and standardized as ISO/IEC 14543-3. A dedicated twisted-pair cable runs alongside mains to every switch, actuator and sensor; the same pair carries data and ~30 V DC power for most bus devices.
Its architecture is the opposite of every hub system on this site: fully decentralized. Each device stores its own configuration, so there is no controller to fail — a KNX wall switch keeps driving its dimmer if every server in the house is off. Configuration happens once, in the licensed ETS software, almost always by a certified integrator. That is KNX's trade: unmatched reliability and a genuinely vendor-neutral catalogue of hundreds of manufacturers, in exchange for professional installation and the highest upfront cost in home automation.
KNX is not sealed off from the wireless world: a KNX IP interface bridges the bus to Ethernet, and from there Home Assistant's first-class KNX integration (or vendor gateways) connects it to voice assistants and to Matter-era devices.
KNX at a glance
| Attribute | KNX |
|---|---|
| What it is | Wired building-automation bus (with RF and IP variants); decentralized — no central controller |
| Standard & since | 1999 — KNX Association, Brussels, merging the older EIB, EHS and BatiBUS standards; ISO/IEC 14543-3 since 2006 |
| Radio / medium | Primarily a wired twisted-pair bus (~30 V DC, powers many devices); also KNX RF (868 MHz), powerline, and KNX IP over Ethernet |
| Network topology | Bus (line/tree): up to 64 devices per line segment, lines joined into areas — installations scale to tens of thousands of devices |
| Data rate | 9.6 kbit/s on twisted pair — tiny, and entirely sufficient for switching and sensing |
| Typical indoor range | Up to 1,000 m of cable per line segment |
| Practical network size | Tens of thousands of devices in one installation |
| Battery devices | Rare — the bus itself powers most devices |
| Required hardware | The bus, a power supply, and certified actuators/sensors; programmed with the ETS tool, typically by a certified integrator |
| Cross-brand interoperability | Excellent and vendor-neutral — hundreds of certified manufacturers, devices from the 1990s still join today’s bus |
| Matter status | Via gateways — a KNX IP interface plus e.g. Home Assistant, or vendor gateways, exposes KNX to modern ecosystems |
| Typical devices | Wall switches, dimming/blind/HVAC actuators, presence sensors (Gira, Jung, ABB, Siemens, MDT, Hager) |
| Device cost | Highest — budget per room and per installer day, not per gadget |