Solar PV

Micro-inverter failure symptoms

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

Your total solar generation is lower than usual, even though it’s sunny. When you check your monitoring app (e.g. Enphase), you see one or more panels showing as “greyed out” or producing 0W while others are producing 300W+.

What’s normal vs not normal

Normal:

  • Individual panels producing slightly different amounts of power due to shading from a chimney or tree.
  • Panels taking a few minutes to “wake up” in the morning at slightly different times.

Not normal:

  • A single panel showing as “Offline” or “Error” for several days in a row.
  • A panel’s production dropping to zero suddenly and never returning.
  • The app showing a “Grid Profile Error” specifically for one or two micro-inverters.

Likely causes (ranked)

  1. Communication interference: The micro-inverter is working, but its signal is being blocked by “noise” on your home’s electrical wiring (e.g. from a cheap LED bulb or a large appliance).
  2. Cable connection fault: The AC connector (“Engage Cable”) between the micro-inverter and the rest of the string has come loose or has water ingress.
  3. Internal component failure: A capacitor or transistor inside the micro-inverter has failed, often due to extreme heat.
  4. Panel-side DC fault: The MC4 connectors between the solar panel and the micro-inverter have become corroded or disconnected.
  5. Grid sensing issue: The micro-inverter’s internal relay has failed, and it can no longer “see” the grid to sync with it.

Quick checks you can do safely

  • Check the app: Look for specific error codes in the “Devices” section of your monitoring portal.
  • Check the breakers: Ensure the dedicated solar PV breaker in your fuse box hasn’t tripped (though this usually kills the whole system, not just one micro-inverter).
  • Wait for a reboot: Micro-inverters reset every night when the sun goes down. Check the app the following morning to see if the “dead” unit has come back to life.
  • Check for shading: Is there a new obstruction (like bird droppings or a fallen branch) specifically covering that one panel?

When to call an installer

  • If a micro-inverter remains “Offline” or at 0W for more than 48 hours.
  • If you see multiple micro-inverters failing in a short space of time.
  • If your app shows a “G98/G99 Grid Protection” fault that won’t reset.

Questions to ask your installer

  • “Are the failed micro-inverters covered under the standard 25-year manufacturer warranty?”
  • “Can you perform a ‘PLC noise test’ to see if there is interference on the power line?”
  • “Does the micro-inverter firmware need to be updated remotely?”

Related NetZeroNow tools & guides

FAQs

What is a micro-inverter? Unlike a “string” inverter where one big box handles all panels, a micro-inverter is a small device fixed behind each panel. This means if one fails, the others keep working. How long do they last? They are designed to last 20-25 years, often matching the lifespan of the solar panels themselves. Why do they fail? They live in a harsh environment—extreme heat in summer and freezing cold in winter, right under your roof tiles. Thermal stress is the most common cause of failure. Is my house at risk? No. Micro-inverters have built-in safety shutdowns. If they detect a fault, they immediately disconnect themselves from your home’s power supply. Can I replace it myself? No. Replacing a micro-inverter requires working on your roof and handling high-voltage AC and DC electricity. It must be done by a qualified professional.\n

Written by NetZeroNow | Last updated on 2026-03-02