Fronius Inverter State 306 — Hardware Fault

What Does This Error Mean?

Fronius State 306 is an internal hardware fault — the inverter's self-diagnostics detected a problem with the power electronics. Try a full power-cycle first. If State 306 returns after restart, the inverter likely needs repair or replacement under warranty.

Affected Models

Fronius Primo
Fronius Symo
Fronius Galvo
Fronius SnapINverter Series
Fronius GEN24 Plus

Common Causes

Internal component failure — IGBT transistor, gate driver, or capacitor fault
Sustained overheating causing component damage
Power surge from the grid
Moisture ingress into the inverter
End-of-life failure

How to Fix It

Perform a full power-cycle.

Turn off the AC isolator switch. Set the DC switch on the inverter to OFF. Wait 10 minutes. Turn DC back on, then the AC isolator. Allow the inverter 5 minutes to complete startup and self-diagnostics.
Note whether State 306 returns after restart.

A single State 306 from a transient surge may not return after a restart. If the inverter runs normally for a full day without the fault code returning, monitor it closely but no immediate action is needed.
Take a photo of the inverter display.

Photograph the fault code and any secondary codes shown. The Fronius display may show a more specific sub-code alongside State 306 — this helps the technician diagnose the fault before opening the unit.
Contact your solar installer.

Provide the installer with the serial number (on the label on the inverter casing), the installation date, and the fault code. They will contact Fronius for a warranty assessment.
Check your Fronius warranty.

Fronius Primo and Symo inverters come with a 5-year standard warranty, extendable to 10 or 20 years if registered on Solar.web. If the unit is within warranty, repair or replacement is at no cost.

When to Call a Professional

Yes — State 306 requires a trained technician. Do not open the inverter casing — it contains hazardous DC voltage. Contact your solar installer or Fronius support to initiate a warranty or service assessment.

Frequently Asked Questions

Fronius State 306 after a lightning storm — is it lightning damage?

Possibly — voltage surges from lightning are a known cause of State 306. Check whether your surge protection device (SPD) in the switchboard has activated. If it has, the SPD did its job. Lightning-caused damage may be covered under home insurance rather than the product warranty.

My Fronius inverter is 4 years old and shows State 306 — will it be repaired free?

If it is within the standard 5-year warranty and the fault is not from external damage, Fronius or your installer should repair or replace it at no cost. Contact your installer to initiate the claim.