Shelly EM vs Shelly 3EM: Which Energy Meter for Your Electrical Panel?

Monitoring your home's energy consumption is the first step toward efficiency and cost savings. Shelly offers two popular energy meters: the Shelly EM and the Shelly 3EM. While both provide real-time power monitoring, they serve different electrical setups. This guide compares their features, installation requirements, and use cases to help you decide which one fits your electrical panel.

Whether you have a single-phase or three-phase supply, understanding the differences between these devices is crucial. We'll break down their specifications, clamp options, and practical applications, so you can make an informed choice for your smart home or business.

Understanding the Shelly EM and Shelly 3EM

The Shelly EM is a single-phase energy meter that uses external current transformers (CTs) to measure power. It supports up to two clamps, allowing you to monitor two separate circuits or a single circuit with a higher current rating. The device connects via Wi-Fi and integrates seamlessly with the Shelly ecosystem.

On the other hand, the Shelly 3EM is designed for three-phase systems. It also uses external clamps but supports three phases, making it ideal for homes or businesses with a three-phase electrical supply. Both meters measure voltage, current, power, and energy, but their configurations differ significantly.

• Shelly EM: single-phase, up to 2 clamps, Wi-Fi
• Shelly 3EM: three-phase, 3 clamps, Wi-Fi
• Both offer real-time monitoring and integration with Shelly apps

Key Differences: Single-Phase vs Three-Phase

The most critical difference is the phase support. The Shelly EM is suitable for single-phase systems, commonly found in apartments or smaller homes. It measures the entire load on one phase, providing a complete picture of your consumption. With two clamps, you can monitor two separate circuits, such as a water heater and an EV charger, independently.

The Shelly 3EM, however, is built for three-phase systems, which are typical in larger homes, workshops, or commercial buildings. It measures each phase individually, giving you a detailed breakdown of power usage across all three phases. This is essential for balancing loads and identifying inefficiencies in a three-phase installation.

• Single-phase: Shelly EM – simpler, cost-effective
• Three-phase: Shelly 3EM – comprehensive, phase-by-phase monitoring
• Consider your panel type: check if you have one or three main breakers

Clamp Options: 50A vs 120A

The Shelly EM is often bundled with 50A clamps, which are sufficient for most residential circuits. However, for higher-current circuits like EV chargers or large appliances, you may need a 120A clamp. The Shelly EM supports both, and you can purchase additional clamps separately. For instance, the Shelly EM + 2x 50A Clamp package is a popular choice for standard homes.

The Shelly 3EM also supports various clamp sizes, but it comes with three clamps (typically 50A or 120A). If you have a three-phase EV charger or heavy machinery, the 120A clamps are essential. The flexibility to choose clamp ratings ensures accurate measurement across different load sizes.

• 50A clamps: ideal for standard circuits (lights, sockets, small appliances)
• 120A clamps: for high-load circuits (EV chargers, heat pumps, industrial equipment)
• Both meters support flexible clamp options

Installation and Compatibility

Installing a Shelly EM is straightforward for a qualified electrician. It requires a neutral wire and a power source, and the clamps are simply clipped around the live wires. The device fits neatly into a DIN rail or can be mounted inside the panel. With Wi-Fi connectivity, you can monitor your energy usage from the Shelly app or integrate with home automation platforms like Home Assistant.

The Shelly 3EM installation is similar but involves three clamps, one for each phase. This makes it slightly more complex, but the wiring is still manageable. Both devices are compatible with the Shelly ecosystem, allowing you to create detailed energy dashboards and automate based on consumption. For example, you can set up alerts when a specific circuit exceeds a threshold.

• Professional installation recommended for safety
• Both meters require a neutral wire
• Compatible with Shelly app, MQTT, and home automation systems

Practical Use Cases

For a typical home with a single-phase supply, the Shelly EM is the go-to choice. It allows you to monitor your total consumption and individual circuits, helping you identify energy-hungry devices. If you have a solar panel system, you can use it to track production and consumption simultaneously.

In contrast, the Shelly 3EM shines in three-phase environments. If you have a heat pump, EV charger, or workshop equipment, you can monitor each phase to ensure balanced loads and avoid overloading. It's also valuable for businesses that need to track energy usage across multiple departments or machines.

• Home use: Shelly EM for single-phase monitoring
• Commercial or large residential: Shelly 3EM for three-phase
• Both can integrate with solar systems and EV chargers

Which One Should You Choose?

Your choice ultimately depends on your electrical panel. If you have a single-phase supply, the Shelly EM is the perfect fit. It's cost-effective, easy to install, and covers all your monitoring needs. For three-phase systems, the Shelly 3EM is the clear winner, providing comprehensive data across all phases.

Consider your current and future needs. If you plan to add a three-phase EV charger or heavy equipment, investing in the Shelly 3EM now might save you from upgrading later. Conversely, if you're in a standard apartment, the Shelly EM offers excellent value without unnecessary complexity.

• Check your main breaker: single-phase or three-phase?
• Assess your monitoring goals: total consumption vs phase-by-phase
• Budget: Shelly EM is more affordable, Shelly 3EM offers more features

Both the Shelly EM and Shelly 3EM are top-tier energy meters, but they serve different purposes. By understanding your electrical setup and monitoring needs, you can choose the right device. For single-phase homes, the Shelly EM with 50A clamps is a reliable and affordable option. For three-phase systems, the Shelly 3EM provides the detailed insights you need. Whichever you choose, you'll gain valuable visibility into your energy usage, helping you save money and reduce waste.