Solar installation inspection: process, methods & when it is needed

Inspecting a solar installation means more than looking up at the roof once a year. A complete inspection encompasses the thermographic testing of every module, the electrical check of BOS components and standards-compliant documentation. This article explains what a professional inspection achieves, how it works and what it costs.

What is a solar installation inspection?

A solar installation inspection is a systematic technical check of a photovoltaic system for defects, faults and performance deviations. It differs from a simple visual check in that it is carried out with measuring instruments and specialist equipment and delivers a documented result usable for insurers, warranty claims and maintenance planning.

In practice inspections are carried out to a fixed procedure: visual check, thermographic survey, hand thermography of electrical components and finally a standards-compliant report. Depending on the occasion and requirements the inspection can conclude as a simple condition report or as a complete expert report with an expert opinion.

Inspektionsmethoden im Vergleich

Visual inspection: The simplest and most cost-effective method. Visible: glass breakage, frame damage, gross soiling, visible cable damage and corrosion. Not visible: microcracks, hotspots, PID, internal cell defects, connector problems and most early defects. The visual check is useful as a supplementary measure – wholly inadequate as the sole inspection method.

Elektrische Messungen: Measurement of open-circuit voltage, short-circuit current and insulation resistance per DIN EN 62446-1. Provides information about string performance and insulation quality. Can show deviations at string level but cannot localise which module is defective at module level.

Elektrolumineszenz (EL): Hochauflösende Bildgebung auf Zellebene. Zeigt Mikrorisse, PID und Zelldefekte mit hoher Detailtiefe. Nachteil: Die Anlage muss abgeschaltet sein, die Messung ist zeitaufwendig pro Modul und in der Praxis für große Anlagen schwer umsetzbar.

Infrarot-Thermografie: Full-coverage inspection of all modules during live operation. Detects hotspots, PID patterns, bypass diode faults, connector problems and component defects. With a drone the method scales to any system size. Thermography to IEC TS 62446-3 is the standard for professional inspections.

Ablauf einer professionellen Inspektion

A complete thermographic inspection follows four steps. First comes the preparation: review of system documentation, weather window planning and, where necessary, application for flight permits for the drone survey.

On site the drone thermography is then carried out: GPS-guided survey of all modules with simultaneous IR and RGB camera, 100% module coverage. This is followed by hand thermography of BOS components: inverters, DC junction boxes, string boxes and cable trays are checked for overheating with the IR hand camera. All measurement conditions are logged.

Analysis is carried out to IEC TS 62446-3: all thermograms are geo-referenced, anomalies are classified and documented in the report with site plan, temperature data and recommended actions. The report is typically available within 5 working days after the inspection.

Inspection intervals and legal obligations

There is no direct statutory inspection obligation for PV systems. Indirectly commercial operators are required by the operational safety ordinance to maintain electrical systems safely. Many insurance contracts make regular inspections a condition for full insurance cover – often with explicit reference to VdS 2858.

VdS guideline 2858 recommends thermographic inspection of commercial PV systems every two years. For solar farms and industrial systems a shorter interval often applies. After special events such as hail, storm or surge an unplanned inspection is indicated regardless of the regular interval.

Thermografie als Kernmethode

Infrared thermography is the dominant inspection method for professional PV inspections for three reasons: it inspects every single module of a system of any size without operational interruption, it reliably detects most relevant defect types (hotspots, PID, bypass diodes, BOS defects) and the results can be documented in a standardised format.

For the IEC-compliant inspection defined minimum requirements apply for camera resolution, measurement conditions and report contents. Only an inspection that meets these requirements delivers results usable for insurers and warranty claims.

Was wird im Bericht dokumentiert?

A standards-compliant inspection report to IEC TS 62446-3 contains: geo-referenced thermograms of all modules with GPS coordinates, classification of all thermal anomalies by temperature difference and priority, site plan of the entire system with findings marked, complete measurement conditions log, yield-loss calculation in kWh and euros and recommended actions with priorities. The Premium package additionally includes the expert opinion.

When is an unplanned inspection needed?

The following events require an immediate unplanned inspection regardless of the regular inspection cycle: hail or severe storm events, lightning strike in or near the system, a noticeable yield drop without identifiable cause in the monitoring, fire incidents or fire traces in the system and an imminent warranty expiry without a previously documented condition.

Kosten einer Inspektion

The cost depends on system size and package. The Basic package includes drone thermography with a standards-compliant report. The Complete package adds hand thermography of BOS components. The Premium package additionally includes the expert opinion. All prices are immediately calculable in the price calculator on the homepage including travel costs by location.

Frequently asked questions