German court voids E.ON's district-heating price formulas in three supply areas

On October 12, 2026, the Oberlandesgericht Hamm declared the price-change clauses of E.ON Energy Solutions GmbH unlawful in three district-heating supply areas: Erkrath-Hochdahl, Hamburg-Lohbrügge-Nord and Schwalbach-Limes. E.ON's tariffs run on formulas mixing fixed and variable factors; the ruling found the clauses raised customer prices percentage-wise when purchase costs had risen by a fixed amount, letting fixed cost increases pass through as outsized percentage hikes.

The decision came in the model declaratory action (Musterfeststellungsklage) filed by the consumer federation vzbv, in which more than 7,500 consumers and companies registered before the September 14, 2026 deadline. vzbv had asked the court to void the formulas across all 23 supply areas covered by the action; the judges limited the finding to the three areas and rejected the blanket declaration.

The judgment is not final. Customers cannot claim refunds automatically: registered claimants must wait for legal finality — or bring individual suits — to recover overpayments. vzbv has said it will take the case to the Bundesgerichtshof, and E.ON can appeal as well. The clause design could also reach other district-heating suppliers, whose regional monopolies leave customers unable to vote with their feet.

Clauses voided in three supply areas; 7,500+ claimants registered; refunds possible only after finality, with vzbv appealing to the BGH.

E.ON's formulas applied percentage increases to the whole bill even when only a fixed cost component had moved, so customers paid more than the underlying cost change justified.

District heating is a regional monopoly: customers cannot switch suppliers, so no market pressure constrained the clause design.

The clauses leaned on factors the consumer federation called factually unsuitable, which is what let unusually strong price increases through.

Percentage pass-through formulas quietly overcharge: applying a percentage rise to the whole bill when only a fixed cost moved converts small cost changes into outsized increases courts may void.

vzbv announced it will appeal to the Bundesgerichtshof to extend the finding to the other supply areas, and E.ON may appeal as well. If the finding becomes final, registered claimants can invoke it to reclaim overpaid amounts, with the limitation period on their claims suspended until the case ends. The ruling is being read as a template for challenges to similar percentage pass-through clauses across Germany's district-heating sector.