Reduced solar production - fault finding

My 28 panel system that was installed approximately 13 years ago has been producing approximately 50% less kWh over the past four days. We did have a power outage a few nights ago so not sure if it can be attributed to that or not. What should I be looking to check to see what is wrong (fuses etc)? Typically it would produce about 40 kWh daily but it is now about 1/2 that.

@boneshakin did this suddenly happen? How often do you monitor the system?

40kWh a day is a lot (I’m assuming this is roughly a 6kW system) and I would only expect this much on a long sunny summer’s day. Where are you located and what time of year do you normally see 40kWh?

Have you ever had the system inspected or serviced? There could be a number of reasons why it is not performing. Is there shading from new trees, or a build-up of dirt or mould? Here’s a good article that can help you diagnose a problem before hiring a solar company to inspect the system - Solar system fault finding guide + solutions — Clean Energy Reviews

I found the problem. A blown 15A PV string fuse in the DC-Disconnect.