The gateway connects but register 11000 always times out. Why?

The M-TEC Energy Butler GEN3 changed its Modbus TCP port from 5743 to 502 starting with firmware version 27.52.4.0. Check which firmware your unit runs, then set the portal's port field accordingly. Also confirm the unit ID is 247, not the default 1.

Register 11000 returns a value, but the sign seems inverted. What is correct?

The register is a signed int32. A positive value means the site is importing power from the grid; a negative value means it is exporting. Some third-party tools apply a scale of -1 to flip the convention. In ModbusCloud the raw signed value is preserved: positive = import, negative = export.

I get no response at all, even though the inverter is online. What should I check?

The M-TEC Energy Butler GEN3 internally uses RTU framing over TCP, not standard Modbus TCP framing. Ensure the ModbusCloud Gateway is configured for RTU-over-TCP mode. Additionally, the inverter's own cloud polling can temporarily block external Modbus queries; a brief retry interval of at least two seconds is recommended.

The gateway shows constant zero watts even during peak solar hours. Why?

A reading of zero at register 11000 often means the inverter is in island or standby mode, or that the smart meter connected to the Energy Butler GEN3 is not reporting correctly. Verify the inverter's own display shows a non-zero grid value, and check that the meter on the EMS bus is active and communicating.

Free Modbus template: M-TEC Energy Butler GEN3 (grid)

Name: M-TEC Energy Butler GEN3 (grid)
Brand: M-TEC
SKU: 93bdfdd1-134d-478e-b4de-c5d5768afb7b

The M-TEC Energy Butler GEN3 is an all-in-one hybrid inverter and battery storage system, available from 6 to 20 kW with stackable LFP modules from 7.7 to 30.7 kWh. This template targets the grid measurement role, reading the signed grid exchange power at register 11000 over Modbus TCP via the device's onboard Wi-Fi gateway. A positive value indicates power drawn from the grid; a negative value indicates export. Connecting the ModbusCloud Gateway to the Energy Butler GEN3 gives installers a reliable, cloud-based view of grid power flow without additional metering hardware.