Shelly energy meters connected to your maintenance

Which Shelly to choose

The Shelly Pro 3EM is the three-phase meter for a main switchboard or a large machine: it mounts on a DIN rail, measures three phases with current clamps and connects by Wi-Fi or Ethernet. The Shelly EM Gen3 and the Pro EM-50 measure single-phase circuits — a sub-board, a pump, a cold room. The Plug S Gen3 is a plug with power metering for equipment that plugs into a socket, and the 1PM Gen3 is a relay with power metering that fits behind a switch or in a machine’s enclosure.

All five use the same Shelly Gen2/Gen3 interface, and FreeMaint recognises them automatically. Other Shelly Gen2 and Gen3 devices with power metering also send their measurements; you can set their model by hand on the device page. A licensed electrician must install anything that sits inside a switchboard.

• Pro 3EM — three-phase, DIN rail, Wi-Fi or Ethernet
• EM Gen3 and Pro EM-50 — single-phase circuits
• Plug S Gen3 — plug-in equipment
• 1PM Gen3 — relay with power metering

What maintenance does with the measurements

Power tells you more than a bill. A conveyor motor that draws ten percent more at the same load is often a bearing or an alignment problem before it becomes a breakdown. A compressor that never stops at night points to an air leak. A ventilation unit that draws nothing during opening hours has tripped. Each of these patterns can be watched by an alert rule on the right channel, attached to the right asset.

The same measurements count run hours. Instead of reading a counter on the machine each month, FreeMaint counts the minutes the motor draws power and writes the total into the asset’s meter, by default once an hour. A plan such as a belt check every 500 hours or an oil change every 2,000 hours then triggers on real use.

From the script to the dashboard

The script FreeMaint generates reads the Shelly’s measurements every 60 seconds and sends them to FreeMaint over HTTPS with your access key in a header. If the Shelly reboots after a power cut, Run on startup starts the script again. If you lose the key, generate a new one from the integration and paste the new script; the old key can stay valid for 24 hours while you update the device.

Values sent in watt-hours are converted to kilowatt-hours, so a Shelly and a utility meter add up correctly on the energy dashboard. Each device shows its last message; once you confirm it, FreeMaint flags it as late, then offline, if the script stops.

Plans and what to know before buying

Connecting devices is part of the Business plan, at $99 per month per company, flat, with 100 active channels — enough for many meters, each phase counting as its own channel. FreeMaint sells no hardware: buy the Shelly from the manufacturer or a distributor. The models above carry the Compatible badge, which means they were validated against Shelly’s documentation.