Solar O&M: what to do and how often

• Daily and automated: yield monitoring, inverter fault alarms, comparing output between strings and inverters on the same orientation.
• Monthly: review event logs, investigate yield deviation alerts, clear newly appeared shading.
• Quarterly: module cleaning (depending on local soiling), inspection of mounting structure, fixings and waterproofing.
• Annually: electrical testing, torque checks, thermographic inspection, earthing and surge protection checks, DC string insulation measurement.

Performance ratio (PR) compares actual output with theoretical output derived from measured irradiation, so it reflects operating quality far better than absolute kWh, which moves with the weather. A sustained PR decline is the signal for a site inspection.

• Track PR monthly and against the same month last year to remove seasonality.
• Compare specific yield between inverters on the same orientation to spot an abnormal string.
• Cross-check DC insulation alarms against rainfall to find cable and MC4 connector faults.
• Log downtime and root causes to compute system availability.

• Hot spots from localised soiling, bird droppings or defective cells – found with a thermal camera.
• DC connectors of mismatched brands or insufficiently seated, causing overheating and fire risk.
• New shading: exhaust stacks, cooling towers, a neighbouring building constructed later.
• Insulation degradation from rodent damage, water pooling in cable trays or open conduit ends.

All rooftop work requires working-at-height safety measures and electrical isolation procedures; never clean modules in peak sun or with high-pressure water.

• Committed response time and on-site attendance time for faults.
• A clear scope split between routine tasks and separately charged corrective work.
• Periodic performance reports including PR data, alarm list and corrective actions.
• A mechanism for the O&M provider to handle module and inverter warranty claims on the owner's behalf.