- Which warranty deadlines apply?
- Warranty vs. guarantee – the decisive difference
- BGH ruling: why rooftop systems often have 5 years
- Defects that only become visible after 2–4 years
- What an expert report before expiry achieves
- Concrete procedure: step by step
- Checklist: is your warranty about to expire?
- FAQ
Which Warranty Deadlines Apply to PV Systems?
The statutory warranty on photovoltaic systems is not as straightforward as many operators assume. Which deadline applies depends on how the contract is legally classified. As a rule of thumb:
| Contract type | Typical deadline | Typical scenario |
|---|---|---|
| Works contract (Werkvertrag) with construction reference | 5 years | Rooftop installation firmly connected to the building |
| Purchase contract (Kaufvertrag) | 2 years | Component purchase with minimal assembly |
| Works contract without construction reference | 2 years | Depends on the individual case |
Warranty vs. Guarantee – the Decisive Difference
Both terms are often used interchangeably in everyday life but mean completely different things.
The warranty is a statutory entitlement against your contractual partner – usually the installer or solar company. It obliges them to remedy defects that already existed at the time of handover. The deadline is 2 or 5 years.
The manufacturer's guarantee is a voluntary commitment by the module manufacturer. 10–15 years product guarantee and 25–30 years performance guarantee are typical. It sounds generous but has catches: the guarantor is often based abroad, conditions are frequently restrictive, and enforcement can be costly.
BGH Ruling: Why Rooftop Systems Often Have 5 Years' Warranty
With its ruling of 2 June 2016 (case no. VII ZR 348/13), the Federal Court of Justice (BGH) made an important ruling: if a photovoltaic system is subsequently installed on a building and firmly connected to the fabric, it constitutes work on a structure. This means the five-year warranty deadline applies.
The case concerned a rooftop system on a tennis hall. Over 300 modules were bolted firmly to the roof via a substructure, cables were routed into the building interior and inverters were installed inside. The BGH ruled that separation from the building would only be possible at significant effort and the system extended the purpose of the building.
Defects That Only Become Visible After 2–4 Years
Many technical problems with photovoltaic systems do not appear immediately. The system delivers unremarkable values in the first few months – and the actual defects develop gradually. This is precisely what makes an expert report before the deadline expires so important.
Accelerated degradation: A certain performance reduction over the years is normal. If it significantly exceeds manufacturer specifications (typically max. 0.5–0.7% per year), a material or manufacturing problem may exist. Effects such as PID (potential-induced degradation) or LID (light-induced degradation) sometimes only become measurable after months to years.
Delamination and yellowing: When layers within the module detach or the encapsulant material yellows, light transmission and therefore yield decreases. This often only becomes visible after 3–5 years.
Micro-cracks: Can arise during transport or installation but initially show no measurable effect. Over the years, cracks grow through thermal cycling and spread – until cell sections are electrically disconnected and yield noticeably declines.
Corrosion and connectors: Moisture in poorly installed MC4 connections or non-standard connector combinations causes creeping contact resistance. The result: heating, power loss and, in the worst case, a scorching fault.
Substructure and roof penetrations: Defects in the mounting or inadequately sealed roof penetrations often only show up after several weather cycles – through leaks, loose connections or material fatigue.
What an Expert Report Before Expiry Concretely Achieves
An independent expert report before the warranty expires fulfils three functions:
1. Condition survey: The current technical condition of the system is objectively recorded – electrically, mechanically and documentarily. Not only visible defects are recorded but also anomalies that indicate concealed problems.
2. Evidence preservation: Documentation of defects by an independent expert has a different quality than your own photo collection. A structured report with reference to standards, manufacturer specifications and recognised test methods is the foundation for effectively enforcing warranty claims.
3. Basis for action: The report provides a clear statement on which defects exist, what caused them and what action is required. This enables a targeted remediation request to the installer – with technical substance, not just suspicions.
Concrete Procedure: Step by Step
Step 1 – Determine the deadline: Check your contract, commissioning documentation and final invoice. This determines the acceptance date and therefore the start of the deadline. Plan the expert report at least 3–6 months before the deadline.
Step 2 – Gather documents: Contract, acceptance protocol, string plan, circuit diagram, commissioning protocols, monitoring data, manufacturer data sheets and any prior correspondence with the installer.
Step 3 – Commission an expert: An independent, certified expert conducts the on-site inspection, reviews the documentation and produces a structured report with findings, cause assessment and recommendations.
Step 4 – Issue a defect notice: If defects are found, the remediation request to the installer should be made in writing, specifically and with a deadline – ideally with reference to the expert report. This effectively interrupts the limitation period.
Step 5 – Pursue claims: Depending on the installer's response, an out-of-court settlement, independent evidence proceedings or a claim may make sense. The expert report provides the technical basis in every case.
Checklist: Is Your Warranty About to Expire?
- When was the system accepted? (check the date)
- Is there a written acceptance protocol?
- Which contract type was agreed? (purchase or works contract)
- Was a VOB/B clause agreed?
- Are there yield anomalies in monitoring?
- Are visible defects present? (cables, connectors, modules, substructure)
- Were all installation documents and test protocols handed over?
- Is a complete string plan available?
- Have there been any repairs, remedial work or complaints?
- Are manufacturer guarantees separately secured and documented?
If you are uncertain about more than two points, a technical inspection before the deadline is advisable.
FAQ
Does my PV system have a 2 or 5 year warranty?
It depends on whether the contract is classified as a purchase or works contract and whether the system qualifies as a structure. The BGH ruled in 2016 that rooftop systems firmly connected to the building can qualify as a structure – giving 5 years. Pure component purchase without significant assembly may only give 2 years. If in doubt, seek legal advice.
When does the warranty period start for PV systems?
The period starts with acceptance – i.e. when you acknowledge the installer's work as contractually compliant. This can happen formally via protocol, tacitly through commissioning and payment, or fictitiously after a certain period without a defect notice.
What does an expert report before warranty expiry achieve?
An independent expert report documents existing defects in an evidentially sound manner before your claims expire. This secures your ability to enforce remediation or damages against the installer. Without timely documentation these claims are irretrievably lost.
Which defects typically only appear after 2–4 years?
Typical late defects include accelerated module degradation, delamination, PID effects, creeping yield reduction through string faults, corrosion of connectors, leaks at roof penetrations and substructure problems.
What is the difference between warranty and manufacturer guarantee?
Warranty is a statutory entitlement against your contractual partner (usually the installer) – 2 or 5 years. Manufacturer guarantee is a voluntary commitment by the module manufacturer – often 10–30 years performance guarantee. Both claims exist independently but have different contacts, deadlines and conditions.
Have Your Warranty Checked
Unsure whether your warranty is still running or action is needed? Send your system details – acceptance date, system size, location – and receive a free initial assessment.
Email: info@gutachterpv.org
Note: This article provides technical and factual guidance. It does not replace legal advice. For the legal assessment of your specific case, please consult a solicitor.