Fronius Virtual Inverter — Enable Wattpilot PV surplus charging without Fronius hardware

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Hey everyone,

I've built a custom integration that emulates a Fronius GEN24 inverter and
Smart Meter IP on your local network, enabling Fronius Wattpilot PV surplus
(Eco) charging without needing real Fronius hardware.

Why?

The Wattpilot's Eco charging mode requires a paired Fronius inverter or Smart
Meter IP. Without one it shows error 109. This integration fakes one using
your existing HA sensors.

Works great for:

  • Sites with third-party inverters (Growatt, SolarEdge, etc.)
  • Sites with non-Fronius batteries (Tesla Powerwall, BYD, etc.) —
    maps SOC to unlock Wattpilot's PV battery threshold features
  • Any site that has power flow data in HA

How it works:

  • Serves the Fronius Solar API v1 over HTTP
  • Announces itself via mDNS so the Wattpilot discovers it automatically
  • Optional Modbus TCP Smart Meter IP emulation (port 502)

Tested with:

  • Fronius Wattpilot V2, firmware 42.5
  • Growatt + Shelly 3EM (no Fronius hardware at all)
  • Tesla Powerwall via tesla_custom integration

Install via HACS custom repository:

fronius-virtual-inverter

:warning: Vibe coded with Claude AI — tested on real hardware but use at your own risk!

Feedback and PRs welcome.