Modbus TCP for SCADA

Energy measurements from a SCADA device connected via the Modbus TCP protocol.

To allow Sunreport to read energy and power data from a SCADA, inverter, or datalogger compatible with Modbus TCP, a few connection parameters and Modbus registers must be provided.
These values identify the device address and the registers containing the required measurements.

Required parameters

Device IP

The IP address of the Modbus TCP device from which data will be read.
It can be found in the network settings of the SCADA/inverter or in its web interface.

Example: 192.168.1.50

Energy Register

The Modbus register that exposes the total produced energy (usually in Wh or kWh).
Each device defines its own register address; it may be a 32-bit value (two consecutive registers) or, less commonly, 64-bit (four registers).

To locate it, refer to the device’s Modbus documentation under:
Total Energy, Active Energy, Energy Wh, Energy Produced.

Power Register

The Modbus register that reports the instantaneous active power (W).
This value may be stored in a 16-bit register or a 32-bit register (two consecutive registers).

In the documentation it is usually labelled as:
Active Power, AC Power, Power.

Bits

Number of bits used for the value:

  • 16 bit → 1 register
  • 32 bit → 2 registers
  • 64 bit → 4 registers

This information is listed under “datatype” or “size” in the device’s Modbus table.

How to find the required registers

To correctly obtain the values to enter:

  1. Consult the device’s Modbus map
    Search online for “Modbus map” + brand and model (e.g. Modbus map ).
    The table lists register numbers, data types and units of measurement.

  2. Check the advanced settings of the SCADA/inverter interface
    Some devices show Modbus registers directly in the web panel.

  3. Request the Modbus map from the installer
    The installer typically has the complete documentation.

  4. Verify that Modbus TCP is enabled
    Some devices require enabling port 502 or allowing remote access.

Useful notes

  • Each manufacturer uses its own register numbering scheme.
  • Some devices use 0-based addressing: the documented register may actually respond at the previous register number.
  • If values appear inconsistent, it may be necessary to adjust the data type (signed/unsigned) or the register order (endianness).

In Sunreport

After identifying the IP address, registers and bit size, select the plant and go to:

Plant settings → Connected devices → Add new → SCADA Modbus TCP

Enter the collected values and press Activate.
Once the connection is established, Sunreport will automatically read energy and power from the device.