> For the complete documentation index, see [llms.txt](https://docs.smart-stuff.nl/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.smart-stuff.nl/dsmr-api/koppelingen/fronius-gen24.md).

# Fronius GEN24 integration

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.

{% hint style="warning" %}
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.
{% endhint %}

## 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.

{% hint style="info" %}
If the dongle is not running DSMR-API yet, see [Webinstaller](/dsmr-api/instellingen/webinstaller.md). For an existing DSMR-API installation, see [Software update](/dsmr-api/instellingen/software-update.md).
{% endhint %}

## 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.

<figure><img src="/files/hkjy1sBjA3dnaSzV7LQf" alt="DSMR-API Modbus settings with Fronius SunSpec 203 mapping, device ID 1 and TCP port 502 selected"><figcaption><p>DSMR-API settings used for the Fronius SunSpec meter emulation.</p></figcaption></figure>

## 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.

<figure><img src="/files/sJ3t4RIZjXZBfMxthFvo" alt="Fronius GEN24 Modbus server configured for TCP, port 502, meter address offset 240 and SunSpec int plus SF"><figcaption><p>Modbus server settings in the Fronius technician interface.</p></figcaption></figure>

## 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.

<figure><img src="/files/sdrcFYKw57bRtbWzCyUq" alt="Fronius GEN24 components page showing a green primary meter and a configured battery"><figcaption><p>A successfully connected primary meter is shown with a green status icon.</p></figcaption></figure>

## 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](/dsmr-api/koppelingen/modbus-rtu-tcp.md).