We install both systems, so we have no reason to push one. They solve the same problem two different ways, and the right answer depends on your house, your budget and whether the walls are open.
What they are
KNX is a wired control standard that has been running commercial buildings and high-end homes since the 1990s. Every switch, sensor and actuator sits on a dedicated two-wire bus. Devices come from hundreds of manufacturers and all speak the same language.
Shelly is a family of small WiFi relays and dimmers that sit behind your existing light switch. Your normal switch still works, and the relay also lets the home system control the circuit. No new wiring beyond what is already in the wall.
Both end up controlled from the same place in an ILS system: a local Home Assistant server, one app, one set of scenes.
New build or existing home
This decides most of it.
Existing home: Shelly, almost every time. A retrofit with KNX means new cabling to every switch, which means opening walls and ceilings. Shelly relays fit in the switch box or ceiling rose in minutes each. Same result on your phone, a fraction of the disruption.
New build: either. If the budget stretches, KNX is the more robust long-term backbone. If the budget is tight or the home is modest, Shelly on a properly designed network gives you 90 percent of the outcome for a lot less.
Reliability
KNX wins on paper. It does not depend on WiFi, it has no radio interference, and a 25-year-old KNX install still works. Shelly is reliable when, and only when, the network is designed properly: dedicated access points, a separate network for smart devices, and no consumer router doing the heavy lifting. Most "WiFi smart home is flaky" stories are actually "the ISP router was never going to handle 80 devices" stories.
Cost
Rough installed comparison for lighting only, same house:
- Shelly: relay plus install per circuit is a small line item. A 25-circuit home is comfortably in the low thousands for lighting.
- KNX: actuators, bus power supply, keypads and the extra cabling and labour. Expect several times the Shelly figure for the same circuits.
KNX keypads and glass switches also cost far more than a standard switch, which adds up across a home.
Look and feel
KNX gives you designer keypads and a very "engineered" feel. Shelly keeps your existing switches, so the home looks unchanged unless you add wall displays or scene buttons. Both can drive the same wall displays and phone app.
Future proofing
Both are open. KNX is a formal international standard. Shelly runs local, open protocols and does not need the manufacturer's cloud. Neither locks you into one company, which is the main thing that matters. What you should avoid is any system where the light switches stop working if a subscription lapses or a company shuts down.
What we recommend
- Existing home, any budget: Shelly.
- New build, standard budget: Shelly on a properly designed wired network.
- New build, premium budget or large home: KNX backbone, with Shelly for anything that does not justify a bus device.
- Either way: a local server, real presence sensors, and a network built for the device count.
If you want to see how this plays out on your own plans, send them through on the contact page and we will price both routes room by room. More on how our systems fit together on the services page.
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