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Shelly 3EM

Packet Parser → HTTP
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Last updated: 03. 2026
Shelly 3EM

The Shelly 3EM is a Wi-Fi 3-phase energy meter with three 120 A CT (current transformer) clamps and a built-in 10 A contactor relay. It monitors active power, voltage, current, power factor, and cumulative energy for each phase independently. TapHome communicates with the device over the local network — no cloud connection is required.

Two TapHome templates are available for this device: an HTTP template (default, uses REST API polling) and an MQTT template (uses broker-based message subscription). Both templates provide the same set of devices — 3 energy meters (one per phase) and 1 contactor switch. Choose one protocol based on the installation requirements.

Hardware connection

The Shelly 3EM requires mains power (110–230 V AC) connected to the L and N terminals. Each of the three included CT clamps connects to the CT1, CT2, and CT3 terminals respectively. The contactor relay output is on the O terminal (10 A max).

CT clamp installation
  • Each CT clamp clips around the live wire of the circuit to monitor — no wire cutting required
  • The arrow on the CT clamp must point in the direction of current flow (from source to load)
  • CT clamps can monitor a 3-phase system (L1, L2, L3) or three independent mono-phase circuits

Do NOT connect a CT clamp to the live wire before wiring it to the Shelly 3EM. High voltage may be present across the transformer’s connection cables even if only the transformer is connected.

Contactor control

The relay output (O terminal) is rated for 10 A and can directly switch small loads or drive an external contactor coil for switching higher loads.

Configuration

HTTP template setup

During template import, enter the device’s IP address. The template polls three separate endpoints (/emeter/0, /emeter/1, /emeter/2) for per-phase energy data and /relay/0 for contactor state. Each phase response is cached in a custom variable (emeter0, emeter1, emeter2) to minimize HTTP calls per poll cycle.

MQTT template setup

The MQTT template requires three import parameters:

ParameterDescriptionExample
MQTT Broker IPAddress of the MQTT broker192.168.1.10
MQTT Broker PortBroker port (default 1883)1883
Device IDMAC address suffix used in MQTT topicsB929CC

The Device ID (dID) is the last 6 characters of the MAC address in uppercase hex. It can be found in the Shelly web UI under Settings → Device Info, or via GET http://{ip}/settings → mqtt.id field.

The module subscribes to shellies/shellyem3-{dID}/# and listener scripts route per-phase emeter and relay messages to the corresponding devices.

The MQTT template uses the topic prefix shellyem3-{dID} while official API documentation references shelly3em-{id}. Both formats work — the dID variable is user-configurable. Verify the actual topic prefix by subscribing to shellies/# with an MQTT client.

On Gen1 Shelly devices, enabling MQTT disables Shelly Cloud. Both cannot run simultaneously. This is a firmware limitation.

Device capabilities

Per-phase energy metering

The template creates three electric meter devices — one for each phase. Each meter reads:

  • Active power — instantaneous power in W, converted to kW by the template (÷ 1000)
  • Total energy consumed — cumulative energy in Wh, converted to kWh by the template (÷ 1000)

In the HTTP template, each phase is read from its /emeter/{i} endpoint. In the MQTT template, the values arrive on shellies/shellyem3-{dID}/emeter/{i}/power and .../total topics.

Per-phase electrical parameters

Each energy meter exposes four service attributes:

  • Voltage — RMS voltage (V)
  • Current — RMS current (A)
  • Power factor — ratio of active to apparent power (0.00–1.00)
  • Total returned energy — energy returned to the grid in Wh, useful for solar/PV installations with bidirectional metering
Energy counter reset

Each phase has a Reset total service action that clears the energy counters for that specific phase. In HTTP mode this calls /emeter/{i}?reset_totals; in MQTT mode it publishes reset_totals to the shellies/shellyem3-{dID}/emeter/{i}/command topic.

Contactor switch

The template exposes the contactor relay as a switch device. The relay state is read from /relay/0 → ison (HTTP) or the shellies/shellyem3-{dID}/relay/0 topic (MQTT), and controlled via /relay/0?turn=on|off (HTTP) or the .../relay/0/command topic (MQTT).

Additional capabilities

The Shelly 3EM also provides reactive power (VAR), a measurement validity flag per phase (is_valid), total 3-phase power sum (total_power from /status), WiFi signal strength, device uptime, firmware update status, per-phase overpower thresholds, and historical energy data export (CSV). An auto-off timer is available on the contactor relay. These capabilities can be added in a future template update.

Troubleshooting

Device not responding (HTTP)
  1. Verify the Shelly 3EM is connected to Wi-Fi and has a valid IP address
  2. Open http://{device-ip}/shelly in a browser — if it responds, the device is reachable
  3. Check that TapHome Core and the Shelly 3EM are on the same network / VLAN
No MQTT messages received
  1. Confirm MQTT is enabled in the Shelly web UI (Internet & Security → Advanced — MQTT)
  2. Verify the broker address and port are correct in both the Shelly device and TapHome template
  3. Check the dID custom variable matches the actual device ID — subscribe to shellies/# with an MQTT client to verify the topic prefix the device uses
  4. Ensure the MQTT broker is running and accessible from both the Shelly and TapHome Core
Energy readings show zero or NaN
  1. Confirm CT clamps are properly connected to the Shelly 3EM terminals (CT1, CT2, CT3) and clamped around live wires
  2. Verify the CT clamp arrow points in the correct direction (source to load)
  3. Poll /emeter/0 manually and check the is_valid field — false indicates a disconnected or faulty CT clamp
  4. Check power and total values — if both are 0, there may be no load on that circuit

Gen1 Shelly devices support only 2 concurrent HTTP connections. If TapHome and another system (e.g., Home Assistant) poll the same device simultaneously, communication may become unreliable. Consider using the MQTT template if multiple systems need to monitor the device.

How to install in TapHome

Prerequisites

  • Shelly device installed and powered on
  • Local Wi-Fi network (2.4 GHz)
  • TapHome CCU on the same network

Step 1 — Connect Shelly to Wi-Fi

Option A — Shelly app (recommended):

  1. Download the Shelly app (iOS / Android)
  2. Tap + → Add Device and follow the Bluetooth pairing wizard
  3. Enter your Wi-Fi credentials when prompted

Option B — AP mode (no app):

  1. On first power-up the device creates a hotspot: ShellyXXX-AABBCCDDEE
  2. Connect your phone/PC to that hotspot
  3. Open http://192.168.33.1 → Internet & Security → Wi-Fi Mode - Client
  4. Enter SSID and password → Save

Shelly only supports 2.4 GHz networks. 5 GHz networks will not appear in the scan.

Step 2 — Find the device address

Shelly Gen1 devices support mDNS (Zeroconf). You can reach the device using a hostname instead of an IP address:

1

shelly<model>-<MAC>.local

For example: shelly1pm-AABBCCDDEE.local (MAC address in uppercase hex, no colons).

Recommended: use the TapHome IP Scanner. Open the TapHome app and use the IP Scanner (Settings → Network → Scan). The scanner will discover devices on your network and show both the IP address and the mDNS hostname. Use the hostname instead of the IP address for a more reliable connection — it stays the same even if the device’s IP changes after a router reboot.

Alternative methods to find the IP address:

  • Shelly app: Device detail → Device info → IP address
  • Shelly web UI: Connect to the device AP before Wi-Fi setup — the IP is shown after saving
  • Router DHCP table: Look for a hostname like shelly1pm-AABBCCDDEE

Step 3 — Configure in TapHome

  1. In TapHome, add a new Packet Parser (HTTP) module
  2. Address: enter the mDNS hostname (e.g., shelly1pm-AABBCCDDEE.local) or IP address from Step 2
  3. Port: 80 (default, no change needed)
  4. Import the template — TapHome will poll /status to read device state

HTTP authentication is disabled by default on Shelly devices. If you have enabled login protection, TapHome does not support HTTP Basic Auth at this time — keep auth disabled for TapHome integration.

Available devices

Shelly 3EM Module
Custom Variables
Electric Meter (Phase 1) Electricity Meter Read-only

Phase 1 energy monitoring — active power (kW), cumulative energy (kWh), voltage, current, power factor, and returned energy

numeric Unit: W / kWh
Service Attributes
Power factor
Current [A]
Voltage [V]
Total returned energy [Wh]Energy returned to the grid — relevant for solar/PV installations with bidirectional metering
Service Actions
Reset total

Electric Meter (Phase 1)

Read total consumption
RETURN(todouble(PARSEjson(emeter0, "total"))/1000);
Read demand
RETURN(todouble(PARSEjson(emeter0, "power"))/1000);
Read (module)
VAR response := SENDHTTPREQUEST("/emeter/0");
IF response.IsSuccess
 emeter0 := response.Content;
ELSE
 ADDERROR(response.StatusCode + " (" + response.ReasonPhrase + ")");
 RETURN(NaN);
END
Service Attributes
power factor
RETURN(todouble(PARSEjson(emeter0, "pf")));
Current [A]
RETURN(PARSEjson(emeter0, "current"));
voltage [V]
RETURN(PARSEjson(emeter0, "voltage"));
Total returned energy [Wh]
RETURN(PARSEjson(emeter0, "total_returned"));
Service Actions
Reset total
sendhttprequest("/emeter/0?reset_totals");
Electric Meter (Phase 2) Electricity Meter Read-only

Phase 2 energy monitoring — active power (kW), cumulative energy (kWh), voltage, current, power factor, and returned energy

numeric Unit: W / kWh
Service Attributes
Power factor
Current [A]
Voltage [V]
Total returned energy [Wh]Energy returned to the grid — relevant for solar/PV installations with bidirectional metering
Service Actions
Reset total

Electric Meter (Phase 2)

Read total consumption
RETURN(todouble(PARSEjson(emeter1, "total"))/1000);
Read demand
RETURN(todouble(PARSEjson(emeter1, "power"))/1000);
Read (module)
VAR response := SENDHTTPREQUEST("/emeter/1");
IF response.IsSuccess
 emeter1 := response.Content;
ELSE
 ADDERROR(response.StatusCode + " (" + response.ReasonPhrase + ")");
 RETURN(NaN);
END
Service Attributes
power factor
RETURN(PARSEjson(emeter1, "pf"));
current [A[
RETURN(PARSEjson(emeter1, "current"));
voltage [V]
RETURN(PARSEjson(emeter1, "voltage"));
total returned energy [Wh]
RETURN(PARSEjson(emeter1, "total_returned"));
Service Actions
reset total
sendhttprequest("/emeter/1?reset_totals");
Electric Meter (Phase 3) Electricity Meter Read-only

Phase 3 energy monitoring — active power (kW), cumulative energy (kWh), voltage, current, power factor, and returned energy

numeric Unit: W / kWh
Service Attributes
Power factor
Current [A]
Voltage [V]
Total returned energy [Wh]Energy returned to the grid — relevant for solar/PV installations with bidirectional metering
Service Actions
Reset total

Electric Meter (Phase 3)

Read total consumption
RETURN(todouble(PARSEjson(emeter2, "total"))/1000);
Read demand
RETURN(todouble(PARSEjson(emeter2, "power"))/1000);
Read (module)
var response := SENDHTTPREQUEST("/emeter/2");
IF response.IsSuccess
 emeter2 := response.Content;
ELSE
 ADDERROR(response.StatusCode + " (" + response.ReasonPhrase + ")");
 RETURN(NaN);
END
Service Attributes
power factor
RETURN(PARSEjson(emeter2, "pf"));
current [A]
RETURN(PARSEjson(emeter2, "current"));
voltage [V]
RETURN(PARSEjson(emeter2, "voltage"));
Total returned energy [Wh]
RETURN(PARSEjson(emeter2, "total_returned"));
Service Actions
reset total
sendhttprequest("/emeter/2?reset_totals");
Contactor Switch Switch

Built-in 10 A contactor relay for load switching or external contactor control

boolean
Values / States: ON · OFF

Contactor Switch

Read switch state
VAR response := SENDHTTPREQUEST("/relay/0");
IF response.IsSuccess
 VAR content := response.Content;
 VAR responseHeaders := response.Headers;
 RETURN(PARSEjson(content, "ison"));
ELSE
 ADDERROR(response.StatusCode + " (" + response.ReasonPhrase + ")");
 RETURN(NaN);
END
Write switch state
VAR response := SENDHTTPREQUEST("/relay/0?turn=" + switch(St,1,"on","off"));
IF response.IsSuccess = false
 ADDERROR(response.StatusCode);
END
Connection: Packet Parser → HTTP
Possible improvements (10)
  • Reactive Power — Per-phase reactive power in VAR; available in /emeter/ response and via MQTT topic .../emeter/{i}/reactive_power
  • Measurement Validity — Boolean flag indicating whether CT clamp measurement is valid; useful for detecting disconnected CT
  • Total Power (3-phase sum) — Sum of active power across all 3 phases in W; available in /status but not in per-phase /emeter/ endpoints
  • WiFi Signal Strength — WiFi RSSI in dBm
  • Uptime — Device uptime in seconds; available in /status but template only polls /emeter/ endpoints, not /status
  • FW Update Available — Firmware update flag from /status
  • Auto-off Timer — Auto-off timer in seconds on contactor relay
  • Per-phase Power Protection — Per-phase overpower threshold; could be exposed as service attribute + action
  • Historical Energy Data (CSV) — Per-phase historical data export as CSV; not applicable for real-time integration
  • Reset All Energy History — Clears ALL stored energy history across all 3 phases; more destructive than per-phase reset_totals

Sources