M-TEC Energy Butler GEN3 (pv)
The M-TEC Energy Butler GEN3 is a hybrid inverter and battery storage system combining an integrated inverter (6 to 20 kW) with stackable LFP battery modules from 7.7 to 30.7 kWh. It is deployed in residential and small-commercial PV installations for self-consumption maximisation. This Modbus TCP template reads the PV generation power register (address 11028), giving your ModbusCloud portal a live view of solar yield. Connecting this single data point into dashboards and historical charts helps installers and building owners verify that the solar array is performing as expected day to day.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 1, read only
- Brand
- M-TEC
- Last updated
Registers (1)
1 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor live PV generation power to confirm the solar array is producing at expected levels.
- Track daily and seasonal PV yield trends to detect soiling, shading, or module degradation.
- Alert on sustained zero-watt readings during daylight hours to catch inverter faults early.
- Compare PV output across multiple M-TEC Energy Butler GEN3 sites in the multi-site overview.
- Verify that PV generation ramps correctly after grid reconnection following a power outage.
Installation
Enable Modbus on the Energy Butler GEN3 by confirming the built-in Wi-Fi/LAN module (labelled 'espressif' on your router) is active and reachable on your local network.
Connect the ModbusCloud Gateway to the same LAN as the Energy Butler GEN3, ensuring both devices share network reachability; no RS485 wiring is required for the TCP path.
In the ModbusCloud portal, add a new device, import the M-TEC Energy Butler GEN3 (pv) template, and set the unit ID to 247 (or 252 if using the built-in espressif module); use port 502 on firmware V27.52.4.0 or later, or port 5743 on older firmware.
Spot-check register 11028 in the live register view and confirm the returned value matches the watt reading shown on the inverter display or the M-TEC app during daylight.
Things to watch for
The gateway connects but register 11028 always reads zero or no value.
During night-time or heavy overcast, the PV power register legitimately returns zero. If the value is zero in full daylight, check that the correct slave ID is configured: older firmware typically uses ID 247 while the built-in espressif module uses ID 252. Verify with a Modbus scanner tool before adjusting the portal setting.
Connection times out even though the Energy Butler is on the network.
M-TEC changed the Modbus TCP port with firmware V27.52.4.0: units running that version or later listen on port 502, while older units use port 5743. Check your firmware version in the inverter menu or the M-TEC app, then update the port number in the ModbusCloud Gateway configuration to match.
Values look implausibly large or completely wrong despite connecting successfully.
Register 11028 is a uint32 spanning two consecutive 16-bit Modbus registers. If your framing is set to plain Modbus TCP instead of RTU-over-TCP, the byte and word order may be swapped. The GEN3 uses RTU framing over the TCP transport; ensure the ModbusCloud Gateway is configured for RTU-over-TCP (framer: rtu) rather than native Modbus TCP.
Readings drop to zero randomly for a few seconds during normal operation.
The Energy Butler GEN3 internal Modbus server is known to occasionally refuse or drop a request when the inverter is simultaneously writing to its internal cloud logging service. Increase the Modbus request timeout to at least 5 seconds and configure at least 3 retries in the Gateway settings to reduce missed readings.
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