Sonoff Smart Stackable Power Meter (SPM-Main)

Sonoff Smart Stackable Power Meter (SPM-Main)

The SONOFF SPM-Main is the main unit of the SONOFF Smart Stackable Power Meter system. It connects to the cloud by Wi-Fi or Ethernet and controls up to 32 SPM-4Relay units over an RS-485 bus, which gives up to 128 metered and switchable circuits in one system.

Through the eWeLink app you can see the current, voltage and power of each channel and switch the circuits remotely.

Up to 32 relay units: One SPM-Main can manage up to 32 SPM-4Relay units, each with 4 isolated channels. This makes it suitable for sites with many circuits, such as apartments, shops or server rooms where each load needs its own metering.

RS-485 communication: The main unit talks to the SPM-4Relay units over an RS-485 bus, which supports stable data transmission between the units.

Wi-Fi and Ethernet: The SPM-Main connects to the cloud by 2.4GHz Wi-Fi or by Ethernet, so you can choose a wired connection where Wi-Fi is weak.

Local energy data on microSD: With a microSD card (8GB to 32GB SDHC) inserted, the main unit stores energy usage data locally, and you can export the consumption data from the card.

Who it's for / Works with

Electricians and installers who need to monitor and control many circuits, for example in apartment buildings, shops or offices, using the eWeLink app.

Good to know

The SPM-Main does not work alone: it must be connected to at least one SPM-4Relay unit, which is sold separately.

The microSD card is not included.

Installation must be done by a qualified electrician.

Technical Specifications

📄 User manual: Download the official SONOFF SPM-Main / SPM-4Relay user manual (PDF)

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