Shelly 1PM Mini Gen4 Smart Relay Switch: Compact 8A Power

At 29 x 34 x 16 mm and 18 grams, the Shelly 1PM Mini Gen4 is small enough to disappear inside a wall box behind an existing switch. That's the point. It's an 8A relay with power measurement built in, so it can switch a light or fan and report how much that circuit draws. Retailers quote the metering at about 1 percent accuracy, but I couldn't find that figure on Shelly's own spec page, so treat it as a reseller claim. It talks Wi-Fi, Bluetooth, Zigbee, and Matter, and it's a compact switch that reports back, without the bulk of a plug-in module.

What You Get

Overview

The Shelly 1PM Mini Gen4 smart relay switch (model S4SW-001P8EU) packs multiprotocol control into a footprint smaller than a matchbook. Power measurement is supported, so you can see what a circuit uses. At 29 x 34 x 16 mm and 18 grams, it suits retrofitting into standard electrical boxes where space is limited.

Key highlights include Wi-Fi 6 (802.11ax), Bluetooth 5.0, Zigbee, and Matter compatibility, built on a Shelly ESP-Shelly-C68F chip with 8MB flash. You get local control via an embedded web interface, plus cloud access for remote operation. An internal temperature sensor adds monitoring, and scripting, MQTT, KNXnet/IP, 20 schedules, and 20 webhooks (5 URLs each) cover automation. It's rated for 110-240V AC and handles up to 8A at 240V AC (about 2000W). Shelly specifies 30-70% RH and altitudes up to 2000m.

Load, Ports and Protocol

The relay is a 1-pole, normally open (NO) type with screw terminals (0.5-4 mm2 conductors, 0.4 Nm torque). It has labelled SW (switch input), L, N and O (load output) terminals, and it needs a neutral. Shelly's documentation doesn't call it a dry contact, and the L/O terminal layout points to a switched live output, so don't wire it as a potential-free contact. That differs from the plain Shelly 1 Mini Gen4, which is a dry-contact relay.

Wireless specs: Wi-Fi (802.11 b/g/n/ax, 2412-2472 MHz, <20 dBm, up to 30m indoor/50m outdoor); Bluetooth 5.0 (2402-2480 MHz, <4 dBm, 10m/30m); Zigbee (802.15.4, 2400-2483.5 MHz, <20 dBm, 100m/300m). External protection should be a B or C curve breaker (max 10A, min 6kA interrupt). Here's a quick spec list:

• CPU: ESP-Shelly-C68F
• Memory: 8MB flash
• Max load: 8A at 240V AC (2000W). Shelly's page gives no DC rating for this model.
• Sensors: internal temperature, with overheating, overvoltage, overcurrent and overpower protection
• Operating temp: -20°C to 40°C
• Humidity: 30% to 70% RH

Works With

Shelly lists the device as compatible with Matter, which is its default mode. That should work with Apple HomeKit, Google Home, Alexa, and SmartThings, though we haven't tested it with each. Zigbee and Wi-Fi/Bluetooth are the alternatives, and the Shelly app handles setup.

For tinkerers, MQTT, HTTP webhooks, and scripting allow custom logic, like auto-shutoff on high power draw. Integrate with Home Assistant or other platforms using the local API. Zigbee range is quoted at up to 100m indoors in open air. No batteries required, since it draws power from the line.

Everyday Scenarios

The Shelly 1PM Mini Gen4 turns ordinary circuits into monitored ones. Hidden loads like under-cabinet lights or exhaust fans are a natural fit.

Practical applications include:

• Energy monitoring for a single circuit such as holiday lights or a charger.
• Pumps or small heaters with schedules and power thresholds, within the 8A limit.
• Behind-wall switching of a low-power load via voice commands.
• Overheat or overpower cut-off using the device's own protections.

In retrofits, its tiny size hides easily, adding convenience without remodeling.

Setting It Up

Always power off the circuit first.

1. Wire live and neutral to L and N, the load to O, and an optional switch to SW (consult the manual for diagrams).
2. Power on. Matter is the default mode. Hold the button for 5 seconds for the access point and Bluetooth, or press it 5 times for Zigbee inclusion (3 minutes), per Shelly's knowledge base.
3. Download the Shelly app (iOS/Android) and connect via Bluetooth or Wi-Fi (2.4GHz only).
4. For the web UI, join the device's access point and open 192.168.33.1, then configure MQTT or scripts.
5. A 10-second button hold resets it to factory settings.

Test the relay toggle and power readings. Use schedules for timed operation or link to sensors. Full docs in the app or knowledge base cover troubleshooting.

Advanced Features and Customization

Beyond basics, the Shelly 1PM Mini Gen4 supports 20 schedules and 20 webhooks for IFTTT or custom servers. Scripting lets you write rules like "if temperature is above 30°C and power is above 50W, turn off".

The webhook capability lets it talk to external automation platforms, so it can be a node in a mixed smart home system. Several units on different circuits give you per-circuit readings. Zigbee sensors can join the same network if you pick the Zigbee profile.

Multi-Protocol Notes

The Shelly 1PM Mini Gen4 lists Wi-Fi, Bluetooth, Zigbee, and Matter, so you can match it to the hub you already own. Shelly's knowledge base describes Matter as the default and Zigbee as a switchable profile. It doesn't say whether Zigbee and Wi-Fi can run at the same time, so confirm that before you plan a failover between them. The embedded web interface gives you local control without the cloud, and scripting runs on the device.

Energy Monitoring Notes

The combination of power measurement, internal temperature sensing, and scripting makes the relay more useful than a basic smart plug for circuit-level checks. Shelly's page doesn't give the metering range or accuracy, so for anything billing-related use a calibrated meter. The Home Assistant integration can chart the readings over time.

Who the Shelly 1PM Mini Gen4 Is For

This one's aimed at people comfortable working behind a wall plate. If you want per-circuit power metering hidden inside existing boxes, or you run IoT gear through Home Assistant and want local control (the Shelly setup guide explains how), the 8A Mini Gen4 is an easy recommendation.

Who should pass? The 8A ceiling is the catch. That's roughly 2000W at 240V, plenty for lights, fans, and small appliances, but nowhere near enough for an oven, a water heater, or anything drawing heavy current. For those loads you want the beefier 2PM or a dedicated contactor. There's also the wiring: this goes inside a live box, so if opening a wall switch makes you nervous, hire an electrician or buy a plug-in instead. This page is based on Shelly's published specifications, not hands-on testing.