Product Overview

The Shelly Plus 1PM is a WiFi-operated smart relay switch with built-in power metering. Designed to fit behind standard wall switches, inside junction boxes, or within custom enclosures, it allows users to control a single electrical circuit while simultaneously monitoring its energy consumption. Unlike basic smart plugs that take up valuable outlet space, the Plus 1PM is hardwired, providing a clean, hidden, and permanent smart home solution.

At the heart of the Plus 1PM is the ESP32 microcontroller, a significant upgrade from the ESP8266 found in older generations. This chipset brings enhanced processing power, dual-core capabilities, and native Bluetooth Low Energy (BLE) support. The inclusion of BLE is a game-changer for the initial setup process, eliminating the frustrating WiFi pairing loops that plagued earlier smart home devices. Furthermore, the Plus 1PM supports modern protocols, local API control, and advanced scripting, making it a favorite among advanced users who prefer local execution over cloud dependency.

Hardware Design & Build Quality

Measuring a mere 42mm x 35mm x 16mm, the Shelly Plus 1PM is remarkably compact. This small footprint is critical when retrofitting smart devices into existing European or US-style backboxes, where space is already at a premium due to thick gauge wiring and wire nuts. The outer casing is made of durable, flame-retardant plastic that feels robust and well-constructed.

One of the most notable hardware improvements in the Plus series is the terminal design. Shelly has implemented high-quality, recessed screw terminals that grip wires securely. The layout is logical, clearly labeling Line (L), Neutral (N), and the Load output. The device requires both a Line and a Neutral wire to power its internal ESP32 chip and WiFi radio, which is standard for most modern smart relays but something installers must verify before purchasing.

Thermal management is a 1PM shines shines. High electrical loads generate heat, and smart relays are notorious for throttling or failing if they overheat. Shelly has integrated a built-in temperature monitoring chip directly onto the PCB. If the internal temperature exceeds 95°C (203°F), the relay automatically cut power to prevent melting or electrical fires. Additionally, the device features over-power and over-voltage protection, ensuring your connected appliances and the relay itself are safeguarded against electrical surges.

Setup Experience & App Interface

Historically, setting up WiFi-only smart relays was a tedious process involving connecting to a temporary ad-hoc network, switching back to your home router, and hoping the credentials passed through correctly. The Shelly Plus 1PM completely bypasses this headache thanks to its integrated Bluetooth Low Energy (BLE) chip.

Using the Shelly Smart Control app on your iOS or Android device, the app automatically scans for nearby Shelly devices via Bluetooth. Once discovered, you simply select your home WiFi network, enter the password, and the device is provisioned in seconds. This BLE provisioning is vastly superior to older methods and earns the device high marks for user-friendliness during the initial installation phase.

The Shelly Smart Control app itself is comprehensive, though it can feel slightly overwhelming to beginners due to the sheer volume of settings available. You can configure power thresholds, set up schedules, create scenes, and view detailed historical graphs of your energy consumption. For advanced users, the app provides direct access to local network settings, MQTT broker configurations, and firmware updates. While the app is powerful, the learning curve prevents a perfect score in the setup category, as novice users might find the menu structures a bit dense compared to more simplified consumer apps.

Performance, Scripting & Power Monitoring

The primary function of the Shelly Plus 1PM is to switch a load up to 16 Amps (roughly 3500W at 230V or 1900W at 110V). In our independent testing, the relay actuation is snappy, with virtually zero latency when triggered via the local network. The physical click of the relay is audible, which provides satisfying tactile feedback, though it may be a consideration if installed in a bedroom nightstand where silence is preferred.

Where the Plus 1PM truly justifies its price tag over the standard Shelly Plus 1 is its power monitoring capabilities. The device tracks voltage, current, active power, apparent power, and total energy consumption (kWh). When tested against a calibrated commercial multimeter, the Plus 1PM’s power readings were accurate within a 1-2% margin of error. This level of precision is invaluable for users looking to identify energy-hungry appliances, monitor the consumption of a specific HVAC unit, or track the output of a solar water heater.

For the DIY enthusiast, the Shelly scripting engine is a massive performance booster. Running on mJS (a restricted subset of JavaScript), the device can execute custom scripts locally without relying on cloud servers or external hubs. You can write scripts to create complex logic, such as turning off a space heater if the room temperature (read from another sensor) exceeds a certain threshold, or sending a local HTTP webhook when power consumption drops below a specific wattage, indicating a cycle has finished.

Ecosystem Compatibility & Smart Home Integration

A smart relay is only as good as the ecosystem it lives in, and the Shelly Plus 1PM is arguably the most versatile device on the market in this regard. Out of the box, it works flawlessly with the Shelly Cloud, Amazon Alexa, and Google Home. Voice commands are processed quickly, and routines trigger reliably.

However, the real magic happens when you step outside the mainstream cloud ecosystems. For users building a local smart home, the Plus 1PM natively supports MQTT, making it a perfect fit for Home Assistant, OpenHAB, and Node-RED. The local HTTP API is fully documented, allowing for instantaneous control via simple web requests. This local-first approach ensures that your smart home continues to function even if your internet connection goes down.

Furthermore, Shelly has rolled out firmware updates that enable Matter support over WiFi. This is a monumental feature, as it allows the Plus 1PM to integrate seamlessly with Apple HomeKit, Samsung SmartThings, and any other Matter-compatible devices without requiring proprietary bridges. By future-proofing the hardware with Matter, Shelly has ensured that the Plus 1PM will remain relevant regardless of which smart home hubs you decide to use in the future.

Pros & Cons

To summarize our findings, here is a quick breakdown of the strengths and weaknesses of the Shelly Plus 1PM.

Pros

• Accurate Power Monitoring: Highly precise energy tracking down to the watt.
• Bluetooth Provisioning: Makes initial WiFi setup incredibly fast and frustration-free.
• Local Control & MQTT: Zero latency and complete privacy for advanced smart home setups.
• Comprehensive Safety Features: Over-temperature, over-power, and over-voltage protection.
• Matter Support: Future-proof compatibility with Apple, Google, Amazon, and Samsung ecosystems.
• Custom Scripting: On-device JavaScript engine for complex, local automation logic.

Cons

• Requires Neutral Wire: Cannot be installed in older switch boxes lacking a neutral connection.
• Audible Relay Click: The mechanical switch sound may be disruptive in quiet environments.
• App Complexity: The Shelly Smart Control app has a steep learning curve for casual users.

Frequently Asked Questions

What is the difference between the Shelly Plus 1 and the Shelly Plus 1PM?

The primary difference lies in power monitoring and contact type. The Shelly Plus 1PM includes a built-in power meter to track energy consumption (watts and kWh) and features a standard dry-contact-like output that switches the live voltage. The standard Shelly Plus 1 does not have power monitoring but features true dry contacts, meaning it can switch non-mains voltages (like garage door opener logic boards or low-voltage DC circuits) without passing the mains voltage through the load. If you need to monitor energy usage, the 1PM is the correct choice.

Does the Shelly Plus 1PM require a neutral wire?

Yes, the Shelly Plus 1PM requires both a Line (Live) and a Neutral wire to operate. The internal ESP32 chip, WiFi radio, and Bluetooth module require a constant 110-240V AC (or 12-24V DC) power supply to stay connected to your network. If your existing wall switch box does not have a neutral wire bundled in the back, you will either need to hire an electrician to pull a new neutral wire or look into alternative smart switches designed specifically for no-neutral setups.

Can I use the Shelly Plus 1PM with Home Assistant without the cloud?

Absolutely. In fact, local integration is where the Shelly Plus 1PM excels. You do not need to enable the Shelly Cloud service to use it with Home Assistant. By enabling the local MQTT server on the device or utilizing the native Shelly integration in Home Assistant (which uses local HTTP polling and WebSocket connections), the device communicates entirely over your local LAN. This ensures sub-millisecond latency and keeps your energy data completely private.

Is the Shelly Plus 1PM safe to use with high-wattage appliances like space heaters?

The Shelly Plus 1PM is rated for up to 16 Amps, which theoretically supports high-wattage appliances. However, continuous high loads (like a 1500W space heater running for hours) can generate significant heat at the terminal connections, especially if the wires are not stripped and seated perfectly. Fortunately, the device features built-in thermal protection that will automatically cut the relay if internal temperatures reach 95°C. While it is technically capable, for continuous heavy loads, it is always recommended to use a heavy-duty contactor controlled by the Shelly relay, or ensure the wiring gauge is appropriately thick to prevent terminal heating.

Final Verdict

The Shelly Plus 1PM is a masterclass in smart home hardware design. It takes the foundational reliability of the original Shelly 1PM and modernizes it with the ESP32 chip, Bluetooth provisioning, and Matter compatibility. Whether you are a casual user looking to track the energy consumption of your refrigerator via the Shelly app, or a hardcore Home Assistant enthusiast writing custom local scripts to manage your solar diverters, this device delivers unparalleled flexibility.

While the requirement for a neutral wire and the audible relay click may deter a small subset of users, the overwhelming majority of smart home builders will find the Plus 1PM to be an indispensable tool. Its combination of safety features, precise power metering, and local-first architecture makes it a top-tier recommendation for any smart home electrical upgrade.