# Commission Regulation (EU) No 814/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for water heaters and hot water storage tanks (Text with EEA relevance), Division (b): Solar water heaters

Extent: E+W+S+N.I.

The water heating energy efficiency is calculated as follows:
η wh = 0,6 × 366 × Q ref Q tota
Where:
Q tota = Q nonsol 1,1 × η wh,nonsol − 0,1 + Q aux × CC

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Source: https://www.legislation.gov.uk/eur/2013/814/annex/IV/division/3/division/b (the official version)
Page: https://openlegislation.uk/eu-regulation-2013-814/annex-IV/division-3/division-b
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.