Shelly 1PM x4 vs Shelly Pro 2CB: Which Multi-Circuit Energy Monitor to Choose?

Monitoring energy consumption across multiple circuits is a smart way to reduce waste, lower bills, and keep your home or office efficient. Shelly offers two popular relays for this task: the Shelly 1PM x4 and the Shelly Pro 2CB. Both provide per-channel power monitoring, but they are designed for different installation scenarios and budgets. Choosing the right one depends on your electrical setup, the number of circuits you need to monitor, and whether you prefer a compact DIY-friendly device or a professional DIN-rail solution.

In this buying guide, we break down the key differences between the Shelly 1PM x4 and the Shelly Pro 2CB. We'll cover wiring, power handling, monitoring accuracy, and smart home integration. By the end, you'll know exactly which relay fits your multi-circuit energy monitoring project.

Understanding Multi-Circuit Energy Monitoring

Multi-circuit energy monitoring means tracking the electricity usage of several separate circuits from a single device. This is common in homes with multiple appliances, workshops with dedicated power tools, or small offices where you want to split energy usage by zone. Instead of installing one smart plug per outlet, a multi-relay device lets you control and measure several circuits from one unit, saving space and simplifying wiring.

Shelly's multi-relay devices are ideal for this task because they combine switching and power measurement in one compact form. The Shelly 1PM x4 offers four independent channels, while the Shelly Pro 2CB provides two channels with higher power handling and a professional DIN-rail design. Both report real-time power consumption, voltage, current, and energy usage through the Shelly app or via APIs, making them perfect for home automation and energy management dashboards.

• Track energy per circuit to identify high-consumption devices.
• Automate switching based on energy thresholds or schedules.
• Integrate with home assistant platforms via MQTT, HTTP, or cloud.

Shelly 1PM x4: Compact Four-Channel Monitoring

The Shelly 1PM x4 is a compact relay that fits behind wall switches, in junction boxes, or inside small enclosures. It provides four independent relay channels, each capable of switching up to 8A and monitoring energy consumption. This makes it an excellent choice for controlling and monitoring multiple lights, fans, or small appliances in a single room or apartment. Its small size and easy installation are major advantages for DIY enthusiasts who want to retrofit existing wiring without a full electrical panel upgrade.

Each channel on the Shelly 1PM x4 reports individual energy data, allowing you to see exactly how much power each circuit uses. You can set up automations, such as turning off a channel when it exceeds a certain wattage, or schedule devices to run during off-peak hours. The device works with Wi-Fi and supports both local and cloud control, making it versatile for various smart home setups. For projects where you need to monitor several circuits but have limited space, the Shelly 1PM x4 is a cost-effective solution.

• 4 independent channels, each with 8A switching and monitoring.
• Compact design for installation in tight spaces.
• Ideal for retrofitting existing wiring without a DIN rail.

Shelly Pro 2CB: Professional DIN-Rail Dual Relay

The Shelly Pro 2CB is designed for professional installations, particularly in electrical panels or distribution boards. It features two channels, each capable of switching up to 20A, and provides accurate energy monitoring. Its DIN-rail form factor makes it easy to mount alongside other circuit breakers, ensuring a clean and organized panel. The Pro series is known for its robust build quality, higher switching capacity, and support for advanced protocols like Modbus (with add-ons) and Ethernet connectivity (via additional modules).

While the Shelly Pro 2CB has only two channels, each channel can handle much higher loads, making it suitable for heavy-duty appliances like water heaters, air conditioners, or electric vehicle chargers. The device also offers a higher accuracy in energy measurement, which is crucial for professional energy audits or billing-grade monitoring. If you are building a new electrical panel or upgrading an existing one, the Shelly Pro 2CB integrates seamlessly and provides a reliable, long-term solution for multi-circuit monitoring.

• 2 channels, each with 20A switching and monitoring.
• DIN-rail mount for professional electrical panels.
• Higher accuracy and robust design for continuous operation.

Key Differences: Wiring, Power, and Features

The most obvious difference is the number of channels: the Shelly 1PM x4 offers four channels, while the Shelly Pro 2CB offers two. However, the total power handling is different. The Shelly 1PM x4 can switch up to 8A per channel, meaning a maximum of 32A combined (though you should consider derating for continuous loads). The Shelly Pro 2CB can handle 20A per channel, giving a combined capacity of 40A. For heavier loads, the Pro 2CB is the better choice.

Wiring also differs significantly. The Shelly 1PM x4 is designed for in-wall installation, with screw terminals that accept solid or stranded wires. It requires a neutral wire (as do most energy monitoring relays). The Shelly Pro 2CB is DIN-rail mounted and uses a more permanent wiring setup, often with a separate power supply or direct connection to the panel bus. This makes the Pro 2CB more suitable for new installations or professional retrofits where the panel is accessible.

In terms of features, both devices offer the same core monitoring capabilities: real-time power, energy, voltage, and current. However, the Pro series includes additional benefits such as support for Ethernet (with add-ons), better heat dissipation, and a more robust enclosure. The Shelly 1PM x4 is Wi-Fi only, which is fine for most homes, but the Pro 2CB can be integrated into more complex networking setups, including commercial buildings.

• Shelly 1PM x4: 4 channels × 8A, compact, Wi-Fi.
• Shelly Pro 2CB: 2 channels × 20A, DIN-rail, professional.
• Choose based on load requirements and installation environment.

Which One Should You Choose?

Your choice ultimately depends on your specific needs. If you are monitoring multiple circuits in a small apartment or a single room, and you want a simple, space-saving solution, the Shelly 1PM x4 is ideal. It allows you to monitor up to four separate circuits, such as lighting, outlets, a water heater, and an HVAC unit, all from one compact device. Its lower per-channel current rating is sufficient for most household loads.

On the other hand, if you are working on a larger renovation or a commercial project, and you need to monitor high-power circuits, the Shelly Pro 2CB is the better investment. Its DIN-rail design ensures a professional installation, and its higher current rating gives you more headroom. Additionally, if you plan to expand your monitoring system later, the Pro series offers better scalability with add-ons for Modbus and Ethernet.

Consider also the total cost: the Shelly 1PM x4 is generally more affordable per channel, making it a budget-friendly option for DIYers. The Shelly Pro 2CB, while more expensive, offers superior build quality and reliability for critical applications. Both devices are excellent choices, and you can mix them in the same project – for example, using the Shelly 1PM x4 for small circuits and the Pro 2CB for heavy loads.

• For 4 small circuits: choose Shelly 1PM x4.
• For 2 high-power circuits: choose Shelly Pro 2CB.
• For a mix, combine both devices in your panel.

In summary, both the Shelly 1PM x4 and the Shelly Pro 2CB are powerful tools for multi-circuit energy monitoring. The 1PM x4 offers four compact channels for everyday loads, while the Pro 2CB delivers two high-capacity channels in a professional DIN-rail package. Assess your circuit count, load requirements, and installation space to make the right decision. For most residential projects, the Shelly 1PM x4 provides the best balance of flexibility and value. Explore the Shelly 1PM x4 in our store to start optimizing your energy usage today.