Sonoff · SPM-Main

Sonoff SPM-Main main unit for stackable power meter system, Wi-Fi, Ethernet

Name: Sonoff SPM-Main main unit for stackable power meter system, Wi-Fi, Ethernet
Brand: Sonoff
SKU: 6920075776973
Price: 949 MDL
Availability: OutOfStock

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Connectivity: Wi‑Fi, Ethernet (LAN cable)
Metered lines: 128
Load switching: Yes

The Sonoff SPM-Main is the main unit of the stackable SPM power meter system: it connects to the router over 2.4 GHz Wi-Fi or Ethernet and runs up to 32 SPM-4Relay modules over an RS-485 bus (sold separately, up to 128 channels at 20 A). It measures nothing on its own; history is written to an 8–32 GB microSD card (not included). eWeLink app, LAN control, white.

No separate hub required

No separate hub is needed: the main unit itself connects to the router and the eWeLink cloud. Without an SPM-4Relay module, however, the system measures nothing (see “Required add-on module”).

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27 specifications from manufacturer documents

We deliver across Moldova. Availability, delivery timing and cost are confirmed with a manager before order fulfilment.

The right choice starts with specifications

Device passport

Specifications checked against the linked manufacturer documents.Checked 18 October 2026

Connectivity and compatibility10

Connectivity — what it means The wireless link or network the device uses. Wi-Fi connects straight to the router; Zigbee, Thread and Bluetooth Mesh work through a hub or gateway.	Wi‑Fi, Ethernet (LAN cable)Wi‑Fi 802.11 b/g/n 2.4 GHz and an Ethernet port. Ethernet works only after the main unit has been added to the eWeLink app (via Bluetooth); it is then used in preference. Bluetooth is used for initial setup only. The main unit talks to the SPM-4Relay modules over a wired RS-485 bus [1]
Hub required — what it means Whether the device needs a separate hub, gateway or coordinator to work in a smart home. If so, it is sold separately unless stated otherwise.	No hub neededNo separate hub is needed: the main unit itself connects to the router and the eWeLink cloud. Without an SPM-4Relay module, however, the system measures nothing (see “Required add-on module”) [1]
Home Assistant — what it means How the device connects to Home Assistant: a built-in integration, a Zigbee coordinator, Matter or the maker’s cloud integration.	Via a separate integrationThe manufacturer's help page mentions a Home Assistant integration without naming it. There is also an official local HTTP API (DIY mode) for custom integrations and Node-RED [2]
Works without internet — what it means Whether the device keeps working over the local network or through a hub when the internet is down. Cloud features (remote access, voice assistants) need the internet.	YesLAN control and local power monitoring are stated; a local HTTP API (DIY mode) is available [1]
App — what it means The maker’s app used to set up and control the device.	eWeLink [1]
Wi-Fi	IEEE 802.11 b/g/n, 2.4 GHz [1]
Ethernet port	Yes [1]
Storage	microSD slot, SDHC cards 8–32 GB (not included) [4]
Bus to modules	RS-485, up to 32 SPM-4Relay modules, total bus length under 100 m, daisy-chain wiring [1]
Apps and integrations	eWeLink; local HTTP API (DIY mode) [3]

Control and features6

Metered lines — what it means How many separate lines or appliances are measured at once, each with its own readings. For modular systems the maximum including add-on modules is shown.	128System maximum: 1 main unit + up to 32 SPM-4Relay modules with 4 channels each. The SPM-Main alone meters no lines; each SPM-4Relay adds 4 lines [2]
Load switching — what it means Whether the device can itself switch the measured load on and off (built-in relay). Without a relay it only shows consumption.	YesThe relays are in the SPM-4Relay modules (on/off, schedules, threshold cut-off per channel). The SPM-Main itself has no load terminals [2]
Measured values — what it means Which quantities are measured and shown in the maker's app. “Energy exported to the grid” means counting production, e.g. from a balcony solar kit. Via a third-party hub some of this data may be missing.	Voltage, Current, Power, energy (kWh)The eWeLink app shows current, voltage and power per channel with history. The local HTTP API also returns active, reactive and apparent power and consumption per 5‑minute interval [3]
Consumption history storage — what it means Where consumption data is kept: in the maker's cloud, on a microSD card, or in device memory. This decides how far back history goes and whether it survives without internet.	microSD cardmicroSD SDHC card, 8–32 GB (not included). The manufacturer states over 20 years of data and up to 20,000 operation logs per device; an image on the same page says “over 180 days”. The in-app operation log covers the last 3 months [4]
Required add-on module — what it means A module without which the device does not measure any load and which is sold separately. If empty, the device works on its own.	SPM-4Relay module — at least one, up to 32 (sold separately) [4]
Overload protection — what it means What happens when current, voltage or power exceed the set threshold: the device cuts the load or only sends a notification. It does not replace the circuit breaker in the panel.	Cuts off the loadWhen set thresholds (min/max power, min/max voltage, max current) are exceeded, the SPM-4Relay channel is switched off, with an optional delay. The manufacturer says it does not replace a circuit breaker [2]

Measurement and detection4

Current sensing method — what it means If current flows through the device, it is wired in series and limited by its own rating; current clamps go around a wire without cutting it; modular systems measure through separate units.	Through separate modulesEach line's current flows through an SPM-4Relay module (L/N in — L/N out per channel) [1]
Maximum measured current per line — what it means Upper limit of current the device measures on one line. It should be at least the rating of the breaker protecting that line.	20 A20 A per SPM-4Relay channel, 80 A total maximum per SPM-4Relay module [1]
Metering accuracy — what it means Measurement error stated by the manufacturer (±%). The smaller the figure, the closer the readings are to the utility meter.	Not stated by the manufacturer
Maximum measured power per line — what it means The highest power the device measures on one line, as stated by the manufacturer.	Not stated by the manufacturer

Power2

Supply type — what it means Which supply the device is designed for: single-phase 230 V (most flats) or three-phase 400 V (some private houses).	Single-phaseEach channel is rated 100–240 V~ with L and N terminals, i.e. a single-phase circuit. The manufacturer says nothing about use in three-phase panels [1]
Supply voltage — what it means The supply voltage (and current, if stated) as the maker gives it. It must match your mains or adapter.	100–240 V AC, 50/60 Hz, 50 mA max [1]

Housing and installation5

Mounting — what it means How and where it is installed: in a wall box, on a wall or ceiling, on a DIN rail, on a table or in a socket.	DIN railThe manufacturer describes the SPM system as DIN-rail mountable in electrical panels; recommended installation height is below 2 m [2]
Neutral wire (N) — what it means Whether the wall box needs a neutral wire. Older wiring often brings only the live wire to the switch; then pick a model that works without N.	RequiredThe main unit is powered through its own L and N terminals [2]
Terminal wire size — what it means Cross-section of copper wire the terminals accept. The line's wire must match the rating of its breaker.	Not stated by the manufacturer
Dimensions — what it means The device’s size in millimetres as the maker states it. Check that it fits the wall box, niche or shelf.	142.5 × 90 × 66.5 mm [1]
Housing material	Polycarbonate PC, flammability class V0 [1]

Operating conditions1

Operating temperature — what it means The air temperature range the device is rated for. The lower limit matters outdoors, on balconies and in unheated rooms.	−10…40 °C [1]

Model and version2

Colour — what it means The housing colour of this model. Other colours in the same series are separate products.	White [4]
Manufacturer certifications	CE (RED 2014/53/EU), FCC Part 15 [1]

Manufacturer documents

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Delivery and stock

We deliver across Moldova. Availability, delivery timing and cost are confirmed with a manager before order fulfilment.

How is payment handled?

A website order is submitted for confirmation without charging your card. The payment method and final amount are agreed with a manager before payment.

Warranty and documents

The warranty is at least 12 months. The exact period and conditions for equipment and installation work are stated in the sales documents and the accepted proposal. Further support is agreed for each project.

Can I return the product?

Current conditions are published on the Return policy page. Email office@casasmart.md with your order number for the steps relevant to your situation. Statutory consumer rights continue to apply.

Delivery, payment and returns

In your home

See consumption. Control what stays on.

A whole-home meter does not show which appliances consume more. Separate monitoring helps reveal habits and useful changes.

See the complete solution

An electrical panel, a washing machine and an electric car charging in the garage — An example routineSee which circuit uses electricity.

What to check before buying

A neutral wire (N) is required: check it is in the back box, the box depth, the rated load and the manufacturer diagram.
Check Wi-Fi band, app, region and internet requirements.

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