Fronius GEN24 integration

Use P1 smart-meter data as a Fronius GEN24 primary meter through Modbus.

This community guide was contributed by DSMR-API user Arnoud and is based on his working Fronius Symo GEN24 installation.

The DSMR-API dongle can present the measurements from the P1 smart meter to a Fronius GEN24 inverter as a SunSpec Modbus meter. This can replace a separate Fronius Smart Meter when the inverter needs grid measurements for functions such as battery charging and discharging control.

This is a community-tested configuration, not an official Fronius installation guide. Changing the inverter configuration requires the Fronius technician password. Follow the Fronius safety and commissioning instructions, especially when installing or configuring a battery.

Requirements

• An RS485-capable P1 Modbus Pro/NRG dongle running DSMR-API firmware 5.8.1 or newer.

• A Fronius inverter that supports a SunSpec meter through Modbus. This guide was tested with a Fronius Symo GEN24.

• An RS485 connection between the dongle and the Fronius meter interface. Follow the connection diagrams supplied with both devices for the correct A/B terminals.

• The dongle and inverter must also be reachable on the local network for configuration.

• Access to the DSMR-API settings.

• The technician password for the Fronius web interface.

If the dongle is not running DSMR-API yet, see Webinstaller. For an existing DSMR-API installation, see Software update.

1. Configure DSMR-API

Open the dongle web interface and go to Settings > Modbus. Configure:

Setting	Value
Modbus Mapping	15 - Fronius SunSpec 203
Modbus ID	1
Modbus Port (TCP)	502
Modbus Baudrate (RTU)	9600
Modbus Parity (RTU)	8N1

Save the settings and reboot the dongle.

DSMR-API settings used for the Fronius SunSpec meter emulation.

2. Configure the Fronius Modbus server

Open the Fronius web interface and sign in as a technician. Go to Communication > Modbus and configure:

Setting	Value
Mode	TCP Server
Meter Address Offset	240
SunSpec Model Type	int + SF
Modbus Port	502
Allow Control	Enabled

Save the configuration.

Modbus server settings in the Fronius technician interface.

3. Add the meter in Fronius

Go to Device Configuration > Components and add a Fronius Smart Meter (Modbus RTU) as the Primary meter at the grid connection point. Add and commission the battery as described in the Fronius documentation, if applicable.

After saving, the status icon next to the primary meter should be green. A red icon indicates that the inverter cannot read the emulated meter.

A successfully connected primary meter is shown with a green status icon.

Troubleshooting

• Check the RS485 A/B polarity. Terminal naming can differ between manufacturers, so verify it in both device manuals.

• Verify that the DSMR-API mapping is Fronius SunSpec 203 and that Modbus ID 1 is used.

• Verify the RTU settings 9600 and 8N1.

• Temporarily enable the DSMR-API Modbus monitor to confirm that the inverter is requesting registers.

• Confirm that the P1 telegram is being received correctly before troubleshooting the Fronius connection.

• If the meter remains red, reboot both devices after saving the settings and check the Fronius event log.

For general Modbus information, see Modbus RTU/TCP.