Warning What does this mean?

Your system is down or running degraded, but this is not an immediate safety danger. Work through the safe steps below.

Fronius Inverter STATE 301 — What an AC Overcurrent Means

STATE 301 means your Fronius inverter detected an overcurrent on its AC output and briefly interrupted grid feed-in to protect itself. The inverter restarts on its own — a one-off 301 after a grid disturbance is usually nothing to worry about. If it keeps returning, the inverter needs professional attention.

What should I do first?

Two quick questions — we'll point you to the right starting point.

Is this code still showing on your inverter's display?

What this code means

Fronius documents STATE 301 as "Overcurrent (AC)" — the current flowing out of the inverter toward the grid momentarily exceeded the allowed limit. Think of it as a circuit breaker tripping inside the inverter: rather than keep operating outside its safe envelope, the unit stops feeding power for a short time.

What happens next is automatic. The manual's described behavior is a short-term interruption while feeding energy into the grid, after which the inverter resumes its startup routine and — if conditions are normal — goes back to full operation. You don't need to acknowledge anything or press any buttons for a single event.

A one-off 301 is most often triggered by something outside your system: a brief grid voltage disturbance, a switching event on the utility network, or a passing transient. The protection did its job and the inverter moved on. The pattern is what matters. An occasional 301 with months between events is unremarkable. A 301 that appears repeatedly, clusters around certain times of day, or leaves the inverter unable to resume feeding power suggests a real problem — on the AC side, in the grid connection, or inside the inverter itself — and that is when the manual's guidance applies: if the status code persists, contact a Fronius-trained service technician.

What is this downtime costing you?

Rough estimate while your system isn't producing. Adjust the numbers to match your setup.

System size (kW) Peak sun hours / day Electricity rate ($/kWh)

–per day

–per week

–per 30 days

≈ – kWh of lost production per day.

Estimate only — assumes ~80% real-world output vs. nameplate. Actual losses depend on weather, shading, panel direction, and your tariff.

Common causes

['Brief grid voltage disturbances or transients causing a momentary current spike on the AC output.', 'Utility switching events — capacitor banks, tap changers, or fault-clearing elsewhere on the network.', 'Storm-related grid instability, including lightning-induced surges on the distribution network.', 'Loose or deteriorating AC connections creating intermittent high-resistance points (installer diagnosis only).', 'An internal inverter fault — current sensing or power-stage issue — if 301 recurs frequently without any external cause.']

Safe steps to try

Work top to bottom, ticking off each step as you complete it. 0 of 1 done.

['Watch whether the inverter resumes feeding power by itself — automatic restart after a short interruption is the designed behavior for 301.', 'Check Fronius Solar.web for the pattern — a single event after a storm or known grid work is normal; clusters of events are not.', "If the inverter seems stuck and won't resume, switch the external AC disconnect off, wait about a minute, and switch it back on, then allow time for the startup routine.", 'Note the time of each event and anything happening on the grid (outages, flickering lights, utility work) to report to your installer.', "Do not open the inverter or adjust any internal settings — repeated overcurrent trips are a technician's diagnostic job, not a homeowner's."]

Is your inverter still under warranty?

Before paying for a repair, check — your installer may fix this free.

Brand Year installed

Based on typical standard warranty terms — always confirm with your warranty card or installer paperwork, as terms vary by model, region, and purchase date.

When to call an electrician

Contact a Fronius-trained service technician if STATE 301 appears repeatedly, the inverter fails to resume feeding power after an event, or 301 starts appearing alongside other fault codes. Per the manual, a persistent status code requires a trained technician, who can inspect the AC connection, check firmware, and test the inverter's current sensing and power stage. Repeated overcurrent protection trips can indicate a developing hardware problem — don't wait for it to become a permanent failure.

Frequently asked questions

Did the overcurrent damage my inverter?

Almost certainly not from a single event — the protection tripped precisely to prevent damage. It is repeated, unexplained events that deserve investigation, because they can signal a developing fault.

How is 301 different from a grid voltage fault like 102 or 103?

Grid codes such as 102/103 react to the grid's voltage or frequency leaving permitted limits. STATE 301 reacts to the inverter's own output current spiking too high, whatever the underlying cause.

Should I reset the inverter after a 301?

You don't need to — it restarts itself by design. Only cycle the external AC disconnect if the inverter appears stuck, and call your installer if the code keeps coming back.

Can my home appliances cause a 301?

Rarely. STATE 301 concerns the inverter's output current to the grid, which is on a different part of the circuit from your household loads. Grid-side events are the usual trigger.

Need a professional?

This fault may need professional diagnosis. Contact a qualified solar electrician in your area.

Sources: meaning and troubleshooting verified against the manufacturer's documentation — Fronius Symo / Fronius Eco Operating Instructions (manuals.fronius.com/html/4204101909), Class 3 status code table — 301 'Overcurrent (AC)'