Inspecting a PV system before warranty expiry – why it is worthwhile
The warranty period for a PV system in Germany typically expires after five years. After that, defects that should have been remedied earlier must be rectified at the operator's own expense. What many operators do not know: numerous defects are not detectable by the naked eye – microcracks, cell degradation, delamination, faulty connectors. A thermographic inspection shortly before expiry is the only method that documents all hidden damage without gaps and secures your rights against the installer.
Warranty periods for PV systems – what you need to know
The statutory warranty for PV systems is legally more complex than for many other products. PV systems that are firmly attached to the building – which is essentially all rooftop systems – are legally regarded as a structure or part of a structure within the meaning of § 634a BGB. This has an important consequence: the warranty period is 5 Jahre ab Abnahme – not 2 years as for moveable goods.
The acceptance inspection is the formal act by which you take delivery of the system from the installer and confirm that it meets the agreed requirements. The date of acceptance – not the date of commissioning – is the starting point of the period. If you have no written acceptance log, the date of commissioning generally applies.
Gewährleistung vs. Herstellergarantie – zwei verschiedene Ansprüche
Many operators confuse warranty and manufacturer guarantee. Both exist in parallel but are directed at different parties and cover different matters.
Die Gewährleistung is a statutory right against your installer. They are liable for defects that arose during installation: incorrectly oriented modules, faulty wiring, inadequate mounting, non-standards-compliant workmanship. The period runs for 5 years from acceptance.
Die Herstellergarantie is a voluntary undertaking by the module manufacturer. Typical today are 10–12 years product guarantee (against manufacturing defects) and 25 years performance guarantee (at least 80% of rated power). These guarantees apply independent of the installer and must be directed at the manufacturer.
A thermographic inspection before warranty expiry helps to beide Ansprüche secure: it identifies installation defects (warranty claim against the installer) as well as product defects (guarantee claim against the manufacturer) – and distinguishes both damage categories in the report.
Typical defects after 3–5 years of operation
Practice shows which defects are most commonly found in the warranty inspection. The range extends from obvious installation errors to subtle quality defects that only appear after several years of operation.
Microcracks and mechanical cell damage frequently arise from improper transport or installation. They are not visible without thermography but cause measurable power losses. In the thermogram they appear as local thermal anomalies – a clear installation defect if they were already present at commissioning.
Hotspots from cell mismatch occur when modules with different cell characteristics are combined in a string – a common planning error. Individual cells become loads and produce heat instead of electricity. The affected modules show characteristic patterns in the thermogram.
Fehlerhafte Steckverbindungen (MC4 connectors) are one of the most common sources of fire in PV systems. When connectors are not fully seated or are incorrectly polarised, contact resistances arise that are visible as heat points in the thermogram. This is a classic installation defect.
Delamination – the detachment of the encapsulation film from the solar cells – can arise from faulty lamination parameters in production. In the thermogram delaminated areas appear as bright, irregular surfaces. Extensive delamination is generally a manufacturing defect of the module manufacturer.
Errors in the mounting structure – such as insufficiently secured clamps, inadequate corrosion protection measures or incorrectly dimensioned support profiles – are not thermographically visible defects, but are part of a complete acceptance inspection.
Why thermography is the only suitable inspection method
The question of which method is best for carrying out a warranty inspection is quickly answered: only thermography captures all relevant electrical defects across the entire site, non-invasively and during live operation. Other methods such as visual inspection or performance measurement at the inverter have considerable limitations.
Visual inspection detects glass breakage, frame damage and gross wiring errors – but not microcracks, hotspots or faulty connectors behind cable covers. Performance measurement at the inverter shows whether the system overall falls below expectations – but not which modules are affected and why.
Drone thermography to IEC TS 62446-3 solves this problem: it captures every single module with calibrated infrared cameras, classifies anomalies by temperature difference and priority and documents findings geo-referenced in the site plan. The result is a technical document that can be used as evidence in court.
When to inspect – the optimal timetable
The optimal time for the thermographic warranty inspection is 3–6 months before the deadline expires. This gives sufficient time for all subsequent steps: documenting findings, informing the installer, requesting remediation and – if there is resistance – initiating legal action.
Do not wait until the last month before the deadline expires. If you then find defects and the installer refuses the rectification or needs time, the deadline can expire before the problem is resolved. An early inspection gives you the stronger negotiating position.
Practical recommendation: schedule the thermographic inspection for spring or autumn – in these seasons the measurement conditions (sufficient irradiance, moderate wind) are most reliably plannable in northern Germany.
Warranty inspection process at Charged Elements
Unterlagen zusammenstellen
Keep ready: acceptance log or commissioning date, system schematic (string plan), warranty documents from the installer and, where applicable, previous monitoring analyses with performance deviations.
Thermografie-Inspektion
Standards-compliant drone survey of all modules to IEC TS 62446-3, supplemented by hand thermography of all BOS components depending on the package. The system continues to operate normally during the inspection.
Report and findings communication
You receive the complete IEC-compliant report with all findings, classified by urgency. On request we prepare a draft defect notice for communication with the installer.
Follow-up inspection after defect remediation
If the installer carries out rectifications we recommend a final control thermographic inspection that confirms the defects have actually been remedied. This protects against subsequent claims after the deadline has expired.
What to do when defects are found?
When the thermographic inspection identifies defects that indicate installation or production errors a structured approach is recommended. First you should inform the installer in writing of the findings – ideally with a copy of the thermographic report as an attachment. Set a reasonable deadline for rectification (typically 4–6 weeks).
When the installer disputes the defects or delays the rectification the thermographic report to IEC TS 62446-3 is the decisive piece of evidence. It has been produced by an independent party, carried out to an internationally recognised standard and documented geo-referenced – this makes it more reliable than any personal observation.
For product defects attributable to the manufacturer direct the guarantee claims in parallel directly to the manufacturer – with the report as evidence. Many manufacturers already require a standards-compliant thermographic analysis as a prerequisite for guarantee claims.
Frequently asked questions
How long does the warranty apply for PV systems?
For PV systems on buildings the structure-specific warranty period of 5 years from acceptance applies (§ 634a BGB). For individual components the period can be 2 years. Manufacturer guarantees (product guarantee and performance guarantee) are to be considered separately from this.
When should I commission the inspection?
Ideally 3–6 months before the deadline expires. This leaves sufficient time to document findings, inform the installer and have defects remedied within the warranty period.
What does a warranty inspection by thermography cost?
For a commercial system of 50–100 kWp between €599 and €1,149 net. Compared with the value of defects not asserted this investment is generally economically worthwhile.
What is the difference between warranty and manufacturer guarantee?
The warranty is directed against the installer for installation defects; the manufacturer guarantee is a voluntary undertaking of the module manufacturer. Both claims exist in parallel and are to be asserted independently of each other.
Affected? We can help.
Charged Elements GmbH – standards-compliant thermographic inspection to IEC TS 62446-3. Hamburg and northern Germany.
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