Non-conformity in solar panel installations: leaks, the right to cure and conversion
Innodura fits 26 solar panels with the wrong mounting — leaks follow
In August 2018 buyers enter into an agreement with Innodura B.V. for the supply and installation of 26 solar panels on their home, for an amount of €9,545.95 excluding VAT. Innodura subcontracts the installation to Solarmere B.V. The panels are fitted in September 2018. During the course of 2019 the buyers discover a leak in the attic.
They report the leak to Innodura. A fitter attends, but cannot establish the cause. Several repair attempts follow in the autumn of 2019: holes are sealed with mastic, damage is patched over. The leak persists. In December 2019 an independent expert firm (Top Expertise) issues its report: the mounting rails have been screwed to the PVC roof and sealed with mastic, whereas a PVC roof requires specific roof anchors or PVC profiles. The screws with mastic can cause cracks. The expert estimates the repair costs at €5,500.
Conversion notice stands after conditional repair offer
On 8 January 2020 the buyers' representative gives Innodura notice of default: repair within 21 days, failing which they will have it carried out by a third party at Innodura's expense. Innodura does not respond within the period. On 29 January 2020 the buyers convert their claim for repair into a claim for substitute damages — the so-called conversion notice under Section 6:87 DCC. As a matter of goodwill, Innodura is given a further seven days to confirm that it will carry out the repair itself.
Innodura then has a counter-expert report carried out (April 2020), but this does not refute the conclusions of Top Expertise. On 18 May 2020 the buyers give Innodura a final chance: to confirm within seven days that it will arrange a proper repair. Innodura responds on 19 May 2020: subcontractor Solarmere is willing to attend on 12 June — but only if the leak was caused by the panels. In a letter of 27 May 2020 Innodura further suggests that the layout plan altered by the buyers might be the cause.
The Court of Appeal holds that this was not an unconditional undertaking. Innodura made repair dependent on further investigation into the cause, implicitly disputed the expert report, and suggested that the repair could be completed in a single day — whereas scaffolding was needed to remove the panels and refix them. The conversion notice of 29 January 2020 had therefore become irrevocable: the buyers retained their right to substitute damages and were entitled to engage a third party for the repair.
The buyers requested two quotations: Solention (€8,791.38 including VAT) and I.B.W. (€8,762.20 excluding VAT). They chose the lower quotation, which the Court of Appeal considered to be in line with market rates. The Court of Appeal awards the actual invoice amount of €8,791.38 — not the expert estimate of €5,500. The subdistrict court had earlier taken the estimate as its starting point, but the Court of Appeal finds that Innodura had not disputed, with reasons, the actual repair costs (scaffolding, removal of panels, fitting of roof anchors, reinstallation). In the indemnity proceedings Solarmere is held liable as subcontractor: it chose the wrong mounting materials, knew that it was a PVC roof, and had for months failed to respond to Innodura's requests.
What does this mean for buyers and installers of solar panels?
The solar panel market generates a stream of disputes. The case law shows a pattern in which three questions are central: is there non-conformity, has the buyer given the installer sufficient opportunity to cure, and how are the damages assessed?
Not every imperfection amounts to non-conformity. A recent decision of the District Court of Central Netherlands (ECLI:NL:RBMNE:2026:1247) illustrates that minor damage to delivered solar panels does not automatically amount to non-conformity, particularly where the panels function properly. The threshold lies at a defect that renders the panels unfit for the use for which they are intended. Faulty mounting materials that cause a leak clear that threshold comfortably.
The opportunity to cure works both ways. The District Court of Gelderland dismissed a damages claim in a case in which the client had given the contractor insufficient opportunity to remedy the defects and the contractor was thereby released from its obligation (ECLI:NL:RBGEL:2025:304). The Innodura judgment shows when that situation is in fact reversed: several failed repair attempts over a period of more than a year, followed by an unconditional conversion notice, deprive the installer of its right to cure definitively. A conditional or half-hearted offer does not restore that right.
As regards the assessment of damages, an expert estimate does not set the ceiling. If the actual repair costs turn out higher and the buyer can produce two market-rate quotations, those actual costs are awarded — even where they approach the contract value. Solar panels almost always involve private individuals; in cases of that kind the court examines critically whether the installer actually offered a proper repair. More on disputes of this kind on the consumer litigation page.
Frequently asked questions
When may a buyer invoke the conversion from repair to damages?
Under Section 6:87 DCC the creditor may convert its claim for performance into a claim for substitute damages once the debtor is in default. In a consumer sale, Section 7:21 DCC provides that the buyer is entitled to repair or replacement; only after a reasonable period for repair may the buyer switch to damages. Failed repair attempts followed by a notice of default are the usual route to this.
Does an installer lose its right to cure if it makes a conditional offer?
Yes, in principle it does. Where the buyer has already issued a valid conversion notice, a right to cure can only be recovered if the buyer expressly relinquishes that right. An offer that makes repair dependent on further investigation into the cause, or that implicitly disputes the conclusions of an expert report, is not an unconditional undertaking and cannot restore the right to cure.
Are the actual repair costs reimbursed or the lower expert estimate?
The actual repair costs are the starting point, provided the buyer shows that those costs are in line with market rates. Two quotations from independent contractors are strong evidence of this. An expert estimate is an indication of the minimum, not the maximum. If the actual works turn out more expensive because the expert underestimated the scope of the work, those additional costs are for the installer's account.
Judgment: ECLI:NL:GHDHA:2024:277, The Hague Court of Appeal 20 February 2024
Cited case law
Courts of Appeal: ECLI:NL:GHDHA:2024:277
District Courts: ECLI:NL:RBMNE:2026:1247 · ECLI:NL:RBGEL:2025:304
See also
- What happens to instalment payments when the contractor fails to deliver up the works?
- Consumer protection
- What happens to instalment payments if the contractor fails to complete?
- Villa renovation terminated: court of appeal awards contractor €89,589 despite missing signature
- More on consumer litigation