It is recommended to declare the design capacity whenever the seasonal space heating efficiency for heating is declared. Only in this way, the end-user and the installer are informed about the design load used to calculate the seasonal space heating efficiency.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.