Sonoff MINI PM Review: The Matter Power Meter That Hides Behind a Socket
Bi-directional metering, a local web console and an open API on one 16A circuit, with no relay to switch anything.
The MINI PM is a pure measuring device. It is a 32 mm module that wires into a single 16A circuit behind a socket or inside a junction box and reports voltage, current, power and accumulated energy without ever switching the load. It suits people who run their own automation platform, because it exposes a local web console, MQTT and a JSON-RPC open API, and it commissions into Home Assistant over Matter or over MQTT discovery with the energy readings intact. Bi-directional metering makes it work on a balcony solar circuit too, and it is one of the cheapest ways to put real numbers on a single appliance. The limits are its scope and its ecosystem reach: one circuit, no relay, and a Matter energy meter device type that most controllers still do not accept.
- Home Assistant users
- Balcony solar owners
- Single-appliance metering
- Budget buyers
Pros
- Bi-directional metering separates consumption from solar production on the same circuit
- Local web console runs on the device itself, with no app and no account
- Open API over HTTP, WebSocket and MQTT for third-party platforms
- Home Assistant gets the full readings over Matter or MQTT discovery
- Cost tracking with fixed or time-of-use rates, plus data export
- Small enough for a standard back box at 32 x 29 x 15.9 mm and 14g
- Threshold alerts, a run completion notification and a maintenance reminder
Cons
- No relay, so it measures the circuit but cannot switch it or shed the load
- One circuit per module, so a whole-panel picture means buying several
- Single-phase only, with no split-phase or three-phase support
- Apple Home cannot add it yet, because the Matter energy meter device type is not handled there
- Sonoff publishes no measurement accuracy figure
- Needs a neutral wire and a wall box at least 60 mm deep
Who is the Sonoff MINI PM for?
This is not a whole-home monitor. It measures one circuit, the one whose line passes through its L and L Out terminals, so the natural job is a single hungry appliance: a water heater, a fridge, a washing machine, an air conditioner or a balcony solar inverter. That makes it a companion to a panel-wide meter rather than a replacement for one, and the obvious buyer is someone who already knows their household total and now wants to know which appliance is responsible. The second audience is the local-control crowd. A local web console, MQTT and a documented JSON-RPC API mean the readings can be pulled straight off the module on your own network, which is exactly what a Home Assistant energy dashboard needs.
What the Sonoff MINI PM offers
Metering is bi-directional, so imported and exported energy stay separate instead of cancelling each other out, which is the difference between a solar circuit that reads as a meaningless number and one that shows production against consumption. The eWeLink app adds electricity cost tracking with a custom currency and rate, fixed or time-of-use pricing, up to a year of energy data that keeps recording while the device is offline, and export of both the energy history and the bill breakdown. Alerts go beyond overload: overcurrent, overpower, overvoltage and undervoltage thresholds, a run completion alert that tells you the washing machine has finished, and a maintenance reminder that accumulates runtime above a power threshold. On the platform side the module is Matter over Wi-Fi and pairs by scanning its Matter code, with Home Assistant reading it over Matter or MQTT, while Alexa, Google Home and SmartThings are reached by adding it to eWeLink and linking the account. For the size, 32 x 29 x 15.9 mm and 14g, it disappears into a back box.
What to know before you buy
The name says non-switch and Sonoff means it: there is no relay, so the module cannot cut the load it measures and cannot shed it when a threshold is crossed. It raises the alert and that is where its job ends. It is single-phase, rated 100-240V at 16A, with no split-phase and no three-phase mode, and it needs a neutral wire plus a wall box that Sonoff recommends be at least 60 mm deep, behind a 16A breaker or RCBO. Sonoff publishes no measurement accuracy figure for it, which is unusual in this category and worth weighing if you plan to settle arguments with the numbers. On the ecosystem side, the Matter energy meter device type is the newest part of the standard and Home Assistant is the controller that handles it today, so Apple Home cannot take the module yet even though nothing on the device side is missing.
Is the Sonoff MINI PM worth it?
For its narrow job it is hard to argue with. Metering one appliance normally means a metering smart plug, which is limited to whatever is plugged in and adds its own relay to the path, or a clamp monitor in the panel, which costs several times more and needs panel access. This module sits behind the socket, costs very little, and hands the data to your own system through a local API rather than a vendor cloud. The reason to spend more is scope: if you want the whole panel, a multi-circuit clamp monitor answers a question this cannot. The reason to spend a little more within the same family is control, since the version with a relay measures the same circuit and can switch it as well.
Frequently asked questions
Can the Sonoff MINI PM switch the appliance it measures?
No. Sonoff sells it as a non-switch product: there is no relay inside and the module cannot control the load. The line simply passes through it so the current can be measured. If you want the same metering plus switching, the MINI ONE PM is the version of this module that carries a relay.
Does the Sonoff MINI PM work with Home Assistant?
Yes, by two different routes. It can be commissioned as a Matter over Wi-Fi device, or picked up through MQTT discovery, and Sonoff's own platform table shows both routes carrying the voltage, current, power and energy readings. The MQTT route also exposes the electrical threshold settings, over-the-air updates and the network indicator.
Can it measure what solar panels produce?
Yes. Metering is bi-directional, so energy flowing out is counted separately from energy flowing in, and the app can record the generation side as a negative value. That is what makes a balcony solar circuit readable instead of showing an absolute number that mixes both directions.
Does the Sonoff MINI PM need a neutral wire?
Yes. Sonoff states the module requires a neutral connection, so it cannot go into a switch box that only carries the line. It is rated 100-240V at 50/60Hz for loads up to 16A, and Sonoff asks for a 16A breaker or RCBO upstream of it.
Can it be used without the cloud?
Yes. A web console runs on the module and is reached from a browser on the same network, with no app installed and no account created, and MQTT keeps the readings flowing to a local automation platform. Energy data also keeps being recorded while the module is offline and syncs once it reconnects.
How many circuits can one module monitor?
One. The module measures the single line that runs through it, which is why it is normally fitted per appliance rather than at the panel. Metering an entire consumer unit means either one module per circuit or a multi-channel clamp monitor built for that job.
