Solar PV producing less: what to check first
Sources checked
Before diagnosing low production, check whether the data are current and cover comparable periods. Missing cloud data need not mean the system stopped generating. Only then assess shading, power limitation or a fault.
Compare energy over the same period
Check the last update time, kWh totals, alarms and equipment availability. Do not divide an annual estimate evenly into twelve months: solar production is strongly seasonal. Weather, snow and daylight differ between comparison periods.
Distinguish a momentary power reading in kW from daily or monthly energy in kWh. Compare a suitable production estimate with the actual roof and operating period rather than an unrelated installation.
Look for documented changes
Review new shadows, roof work, export limits, battery settings and outages. An inverter can deliberately limit output when there is nowhere permitted for surplus to go, so lower production is not automatically a defective panel.
Send the service company generation traces, exact event times and alarms. Do not bypass protection or change grid settings. Professional checks may be needed even if the system still produces some electricity.