Shelly EM Gen3

Device identification

Name: Shelly EM Gen3

Model: S3EM-002CXCEU

Device SSID: ShellyEMG3-XXXXXXXXXXXX

BLE Model ID: 0x1027

Short description

Shelly EM Gen3 is a compact smart energy meter supporting up to two current transformers for
non-contact power monitoring. It allows precise metering of energy consumption and provides real-time
reports through Wi-Fi or cloud-based home automation systems. The device also includes a dry contact relay
for external load control and internal storage capable of keeping minute-level data records for up to 10 days.
With its small size, Shelly EM Gen3 can be installed in standard electrical wall boxes, behind power sockets,
or in areas with limited space, offering flexibility for both residential and commercial monitoring.

Main features

• Compact form factor for flexible installation
• Single-phase, dual-channel energy measurement
• Current transformer connection for non-invasive monitoring
• Integrated dry contact relay for contactor control
• Real-time clock with internal data logging
• Stores up to 10 days of minute-resolution energy data
• Local web interface for configuration, control, and monitoring
• Supports standalone operation or cloud-based control

Use cases

• Power consumption monitoring: Track and analyze real-time energy usage of connected devices.
• Energy efficiency optimization: Identify consumption trends to reduce waste and optimize usage.
• Appliance health check: Detect irregular power draw to identify faulty appliances early.
• Cost management: Estimate and manage the operating costs of specific appliances.
• Space-efficient retrofitting: Install easily in wall boxes or behind sockets for compact setups.
• Remote monitoring: View power data remotely through Shelly Cloud or other cloud services.
• Local monitoring: Use local UI and automation based on real-time or accumulated power consumption.

Main applications

• Residential
• MDU (apartments, condominiums, hotels)
• Light commercial (offices, retail, restaurants, gas stations)
• Government / municipal buildings
• University / college facilities
• Farming and agricultural automation

Simplified internal schematics

EM-Gen3-internal-schematics.png

Connectivity

Wi-Fi

Bluetooth

Protocols

MQTT

HTTP

WebSocket

RPC

Safety function

Internal temperature sensing and reporting

Supported load types

• Resistive (incandescent bulbs, heating devices)
• Capacitive (LED drivers, capacitor banks, electronic equipment)
• Inductive (motors, fans, transformers, compressors, air-conditioners)

User interface

Inputs:

One (Control) button

• Hold for 5 seconds → Enable device access point and Bluetooth connection

• Hold for 10 seconds → Factory reset

Outputs:

LED (monocolor) indication

• AP enabled, Wi-Fi disabled → 1s ON / 1s OFF

• Wi-Fi enabled, not connected → 1s ON / 3s OFF

• Connected to Wi-Fi → Constantly ON

• Cloud enabled, not connected → 1s ON / 5s OFF

• Connected to Shelly Cloud → Constantly ON

• OTA update → ½s ON / ½s OFF

• Button held 5s → ½s ON / ½s OFF

• Button held 10s → ¼s ON / ¼s OFF

The LED indication list is prioritized — each subsequent state overrides the previous one.

Physical

Size (HxWxD): 37×42×16 mm / 1.46×1.65×0.63 in

Weight: EM Gen3: 23 g / 0.81 oz; CT 50A: 50 g / 1.76 oz

Screw terminals torque: 0.4 Nm (3.5 lbf·in)

Conductor size: 0.2–2.5 mm² (24–14 AWG; solid, stranded, and bootlace ferrules)

Strip length: 6–7 mm (0.24–0.28 in)

Mounting: Wall console, Electrical cabinet

Shell material: Plastic

Shell color: White, Charcoal gray

Connectors color: Black

Environmental

Ambient temperature: −20 °C to 40 °C (−5 °F to 105 °F)

Humidity: 30–70% RH

Max altitude: 2000 m (6562 ft)

Electrical

Power supply: 110–240 V~ 50/60 Hz

Power consumption: < 1.2 W

Neutral required: Yes / No

External protection: 2 A, tripping characteristic B or C; 6 kA interrupting rating; energy limiting class 3

Output ratings

Max switching voltage: 240 V~

Max switching current: 2 A / 240 V~

Sensors & Meters

Voltmeter (AC): 110–240 V~ 50/60 Hz

Voltmeter accuracy: ±2%

Ammeter (AC): 0–80 A

Ammeter accuracy: ±2% (2–50 A), ±2% (1–2 A), ±5% (0–1 A)

Compatible current transformers: CT 50A (included); CT 80A

Power & energy meters: Active and apparent power; active and apparent energy; power factor; fundamental active and fundamental reactive energy

Channel-to-channel calibration minimum load: 500 W

No load threshold: 30 VA per channel

Measurement data storage: At least 10 days at 1 min data resolution

Data export: CSV for PQ recorded values; JSON format export via RPC

Internal temperature sensor: Yes

Radio

Wi-Fi protocol: 802.11 b/g/n

Wi-Fi RF band: 2412–2472 MHz

Wi-Fi max RF power: < 20 dBm

Wi-Fi range: Up to 30 m / 100 ft indoors; 50 m / 160 ft outdoors (depends on conditions)

Bluetooth protocol: 4.2

Bluetooth RF band: 2402–2480 MHz

Bluetooth max RF power: < 4 dBm

Bluetooth range: Up to 10 m / 33 ft indoors; 30 m / 100 ft outdoors (depends on conditions)

MCU

CPU: ESP-Shelly-C38F

Flash: 8 MB

Firmware capabilities

Schedules: Yes

Webhooks: 20 (up to 5 URLs each)

Scripting: Yes

MQTT: Yes

Encryption: Yes (Transport level)

Authentication: Yes (Application and transport level)