Solar installation expert report: when it is needed and how it works

A photovoltaic expert report is not bureaucratic formalism – it is the decisive document when it comes to enforcing warranty claims, obtaining insurance payouts or negotiating the fair price when acquiring a system. This article explains when an expert report is necessary, what it contains and what matters when choosing an expert.

When is an expert report appropriate?

There are four situations in which a professional PV expert report is not only appropriate but often indispensable:

Versicherungsschaden: After hail, storm, lightning or fire the insurer requires standards-compliant damage documentation. Without an expert report the operator risks a reduction or refusal of the payout. The expert report documents the extent of damage, the cause and the quantified yield loss.

Gewährleistungsanspruch: Installation defects that occur within the five-year warranty period must be documented to enforce the claim against the installer. An independent expert report is stronger here than an internal log.

Purchase or sale: When acquiring a used system or a solar farm a thermographic expert report provides information about the actual technical condition – independent of the seller's yield projections and maintenance reports.

Yield evidence and disputes: When an operator and installer are in dispute over the contractually compliant condition of a system a court-admissible expert report provides the objective technical basis.

Types of PV expert report

Thermografisches Schadensgutachten: Documents damage after an event (hail, storm, lightning). Contains complete IR survey, classification of all anomalies and yield-loss calculation. Produced to IEC TS 62446-3 and VdS 2858.

Abnahmegutachten: Inspects a new system after installation for installation defects, hotspots and system errors. Starts the warranty period in documented form and is the reference for later comparative inspections.

Gewährleistungsgutachten: Documents defects before the warranty period expires. Decisive here is the proof that the defects were already present at handover or arose from workmanship errors.

Technical Due Diligence: Technical condition assessment for investment decisions. In addition to thermography also encompasses document review, yield data analysis and residual lifetime assessment.

Wie läuft ein Gutachten ab?

A professional PV expert report is structured in three phases. In the preparation phase system documentation, monitoring data and – where available – previous expert reports are reviewed. This creates the basis for a targeted on-site deployment.

At the on-site appointment the complete drone thermography of all modules is carried out under standard conditions (min. 600 W/m² irradiance, wind below 4 m/s). Additionally the hand thermography of all BOS components is carried out – inverters, junction boxes, string boxes. All measurement conditions are logged.

In the reporting phase all thermograms are geo-referenced and analysed, anomalies classified to IEC TS 62446-3 and the expert opinion with damage-cause assessment and yield-loss calculation produced. The finished report is the document presented to insurers, installers and courts.

Thermografie als Gutachten-Grundlage

Infrared thermography is the core tool of the PV expert. It makes visible what electrical measurements and visual inspections cannot show: the thermal condition of every individual cell, the overheating patterns at connectors and the heat distribution at BOS components.

Decisive for usability is standards-compliance. An expert report based on a non-standards-compliant thermography – with insufficient camera resolution or under incorrect measurement conditions – is often not recognised by insurers. IEC TS 62446-3 defines what professional thermography means.

Welche Normen gelten?

Two standards govern thermographic PV expert reports. The IEC TS 62446-3 governs the thermographic inspection: measurement conditions, camera requirements, classification methods and report contents. The VdS 2858 is the guideline of the German insurance industry for electrical thermography and defines what is required for insurance-compliant expert reports. Only when both standards are complied with is an expert report fully usable for insurers and courts.

Was macht ein Gutachten verwertbar?

A court-admissible and insurance-compliant expert report must contain the following elements: geo-referenced thermograms of every module with GPS coordinates, classification of all anomalies by ΔT and priority, complete log of measurement conditions (irradiance, wind speed, module temperature), yield-loss calculation in kWh and euros, expert opinion with damage-cause assessment and evidence of the expert's qualifications. If one of these elements is missing the document can be challenged by the opposing party.

What does a PV expert report cost?

The Premium package with expert opinion starts for commercial systems from €1,076 net and is calculable in the price calculator on the homepage immediately. The price depends on system size and complexity. For complex damage patterns, large solar farms or expert reports with extended requirements (multiple site visits, document review) we prepare individual quotes.

The costs of an expert report usually pay for themselves quickly: a successful insurance settlement for a 200 kWp system after hail damage is typically €30,000–80,000. Against this sum the expert report fee is negligible.

Wie wählt man einen Gutachter?

Three criteria are decisive: first the technical equipment – professional IR cameras with at least 640×512 pixel resolution and GPS geo-referencing. Second, standards-compliant report production to IEC TS 62446-3 and VdS 2858. Third, experience with the system type – an expert who primarily knows rooftop systems is not necessarily suitable for large ground-mounted systems.

Frequently asked questions