Smart relays
Smart relays are small in-wall modules that wire in behind a switch or fitting you already have, adding app and voice control without changing how the wall looks. The retrofit pick when you want to keep your existing switches, in Wi-Fi and Zigbee, for lighting and for anything else on a circuit.
What a relay does
A smart relay sits in the wall behind your existing switch or inside a fitting, switching the load on and off while the original switch keeps working. You get app and voice control, and the wall plate stays as it is. That is what separates a relay from a smart light switch: the switch replaces the plate, the relay hides behind it. It is the cheaper retrofit, and the one that leaves a heritage or architectural plate alone. Most Australian homes wired to AS/NZS 3000 have a neutral at the switch, which is what a relay needs to power itself, so the usual constraint is depth in the wall box rather than the wiring. A licensed electrician does the install, and it is usually under fifteen minutes per relay.
Wi-Fi vs Zigbee
Wi-Fi modules join your home network directly, with no hub to buy and nothing else to set up, which is why a Wi-Fi relay is the usual starting point for one or two circuits. Zigbee modules need a hub or coordinator, but they run on a local mesh where every mains-powered device repeats the signal, so a Zigbee relay gets more reliable as you add more of them rather than less. That makes Zigbee the better answer for a whole-home retrofit, and for anyone running Home Assistant, where local control matters more than convenience. Both give you app and voice control once set up. The practical test: under about five modules on good Wi-Fi, either works. Past that, or anywhere the router sits far from the switch, choose Zigbee.
Dry contact
A dry-contact relay switches a separate circuit rather than mains power, handy for garage doors, gates and heating that expect a momentary signal.
Sizing
Every relay has a rated switching current, and the load has to sit comfortably under it. Across the current Gen4 in-wall range that means about 8 A on a mini module, 16 A on a standard one, and 10 A per channel with 16 A across both on a two-channel module. An LED downlight circuit draws very little, so almost anything covers it. A towel rail, a heater or a pump is where the rating starts to matter, and an inductive load like a motor or a transformer pulls more on start-up than its label suggests. Check the appliance plate first, then the module listing. Confirm there is depth left in the wall box too: a mini module at about 29 x 34 mm fits where a standard 37 x 42 mm one will not.
Switches · 22 products Relays at Synced Australian stock
Filter guide
Which protocol should I pick?
Protocols are the wireless languages smart devices use to talk to each other. Some need a hub, some run straight off your Wi-Fi. Here's what each one means for your setup.
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Zigbee
Low-power meshThe cleanest mesh for a bigger setup. Every mains-powered device repeats the signal, so coverage grows as you add more. Needs a hub like a Hue Bridge or SmartThings.
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Wi-Fi
No hub neededThe simplest way to start. Plugs into your existing Wi-Fi with no extra hardware. Best for a handful of devices; very large setups can crowd the network.
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Ethernet
Wired to your routerThe steadiest connection you can give a device. A cable means no Wi-Fi congestion and nothing to drop out, which is why hubs, panels and cameras so often offer it. The catch is physical: it has to sit within cable reach of a network port.
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Bluetooth
Direct, short-rangeGood for setup and close-range control from your phone. Range is short with no remote access on its own, so it's often paired with a hub or bridge.
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Filter guide
Which module size do I need?
Smart relays come in two builds: in-wall modules that hide behind a switch or power point, and DIN-rail modules that clip into your switchboard. Size decides where it fits.
In-wall
In-wall modules sit inside the wall cavity behind an existing switch or power point. The size decides whether one fits a mounting box that is already crowded with wiring.
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Standard
About 37 x 42 mmThe full-size in-wall module. Fits most Australian wall boxes and mounting brackets, and takes the most common wiring layouts without fuss.
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Mini
About 29 x 34 mmA shrunk version of the same module. Same job, smaller case, so it fits behind a mech in a wall box that is already tight for room.
DIN rail
DIN-rail modules clip onto the standard rail in your switchboard, installed by an electrician. Width is counted in rail slots of 18 mm, the same measure as circuit breakers.
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1 module
One rail slot, 19 mmTakes a single slot on the switchboard rail, the same width as a standard circuit breaker. Shelly Pro 1, 2, 1PM and 2PM are this size.
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3 modules
Three rail slots, 53 mmTakes three slots on the switchboard rail. The bigger cases, like Shelly Pro 3 and Pro 4PM, use the room for more channels and heavier terminals.
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Filter guide
What's a channel?
One channel switches one circuit. A 2-channel relay behind a single plate can run two lights on their own schedules, or a light and an exhaust fan, without needing a second device.
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One channel
Switches one circuitSwitches one thing on its own: a light, a fan, an exhaust.
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Two channels
Switches two circuitsTwo circuits controlled separately, like both halves of a double switch.
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Three channels
Switches three circuitsThree circuits from one module, each on its own control.
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Four channels
Switches four circuitsFour circuits from one module, each on its own control.
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Filter guide
Where does a relay mount?
A relay hides out of sight and makes an ordinary circuit smart. All three options are wired in by an electrician; the difference is where the relay lives.
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In-wall
Behind the switchFits in the wall cavity behind an existing switch or power point. The switch on the wall stays and still works; the relay sits behind it and makes the circuit smart.
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DIN rail
In the switchboardClips onto the standard rail in your switchboard, next to the circuit breakers. Keeps everything in one serviceable spot, which suits whole-home installs and bigger jobs.
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Filter guide
What does energy monitoring do?
The relay measures how much power the circuit is drawing and reports it in the app, so you can see what a heater or pool pump actually costs to run and build automations around usage. Models without it still switch as normal; they just don't measure.
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Energy monitoring
Measures power useMeasures the power the connected circuit is using, so you can see consumption per device in the app. These are the models with PM in the name.
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Switching only
No power measurementTurns the circuit on and off without measuring power use. Choose this where you only need control, not consumption data.
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More about smart relays
Choosing a smart relay switch.
Check your switch box has a neutral
Most relays need a neutral wire to power themselves, and they need enough depth in the wall box to fit behind the existing switch. Newer Australian homes usually have a neutral at the switch; older ones often do not. A handful of no-neutral relays exist if yours is wired the old way.
Match the protocol to your setup
Pick a WiFi relay if you want the simplest path and have no hub. Pick a Zigbee relay if you run Home Assistant or already have a Zigbee coordinator, since the local mesh stays responsive as you add more. Both give you app and voice control once set up.
Decide what you are switching
A standard relay switches a light or powered circuit. A dry-contact relay sends a momentary signal instead, which is what garage doors, gates and some heaters expect. Check the rated amps against the load so the relay is comfortably within its limit.
Common questions
Quick answers before you buy. We test this gear ourselves. Can't find yours? Ask our Melbourne team
Yes. That is the point of a relay. It wires in behind the switch you already have, so the switch keeps working manually while the relay adds app and voice control. The wall plate does not change. If you want a new look or extra buttons, a smart light switch replaces the plate instead.
In Australia, wiring a relay into mains involves work behind the switch, so a licensed electrician should do the install. It is quick for them, often under fifteen minutes per relay. Battery and plug-in options need no wiring if you would rather avoid an electrician.
Most relays handle both. A standard relay pairs with a normal toggle switch, while many also support momentary or push-button switches through a setting in the app. Check the relay's listing if your switch is the press-and-release type, common on stairwells and some bedside controls.
Yes. Relays switch many circuits, not just lighting. With a dry-contact relay you can trigger a garage door, a gate or a heater that expects a momentary pulse, and a standard relay can run an exhaust fan or pump within its rated load. Check the amps before you wire it in.
It is the same thing as a smart relay, and the wording usually means one of two setups. Either a relay wired in behind the wall switch you already have, so the switch keeps working by hand while the relay adds app and voice control, or a switch and relay sold as one unit. On this page it is the first: a module that hides in the wall cavity or the switchboard and makes an existing circuit smart. If you want the plate itself to change, with new buttons or a different look, that is a smart light switch instead.
It depends on the module. Across the current Gen4 in-wall range it is about 8 A on a mini, 16 A on a standard module, and 10 A per channel with 16 A across both on a two-channel module. Lighting circuits sit well under all of those. Where it matters is heating, pumps and motors: check the appliance plate for its rating, and remember an inductive load draws more on start-up than its label says. Every listing states the figure for that model. If the load is close to the limit, size up rather than run the relay at its ceiling.
Only for Zigbee. A Wi-Fi relay joins your home network directly and needs nothing else, so it is the quicker start if you are doing one or two circuits. A Zigbee relay needs a hub or coordinator, which is an extra purchase, and in return you get a local mesh that every mains-powered device strengthens as you add to it. For a whole-home retrofit, or if you already run Home Assistant or a Zigbee coordinator, the hub pays for itself in reliability. For a single hallway light, it does not.