1. Read both warranties
Identify product and power warranties, manufacturer and claims provider. Record model, country, date, any registration and exclusions. The document may offer repair or another remedy under its terms. Clarify testing, transport, removal and reinstallation costs; an advertised duration does not automatically cover the whole job.
2. Distinguish ageing and incidents
A system may gradually lose power or experience faults, damage and interruptions. IEA PVPS explains that ageing models depend on the module and site conditions and do not necessarily follow a linear curve. Have the actual condition assessed rather than applying one annual rate to all panels.
3. Investigate lower generation
Compare periods, weather, shading, dirt, availability and measurement method. Have a qualified professional also check inverter, wiring and communications. Lower feed-in revenue may reflect tariff or consumption changes. The findings should identify measurements and the likely cause before attributing the discrepancy to module ageing.
4. Assess continued use, repair and replacement
Request options compatible with the existing system. Compare safety, available power, total cost and planned roof work. Replacing an inverter does not automatically require new panels, but existing modules need assessment. For expansion, check electrical limits, mounting, space and procedures; equal rated power does not establish interchangeability.
5. Prepare the owner’s records
Keep the invoice, original warranties, serial numbers, plans, tests and service records. Document readings and changes in building use. Before a sale or provider change, identify service contacts and outstanding questions. Certification or glass-glass construction provides technical information to assess; it does not independently guarantee a specific service life.