# Commission Delegated Regulation (EU) No 812/2013 of 18 February 2013 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to the energy labelling of water heaters, hot water storage tanks and packages of water heater and solar device (Text with EEA relevance), Division (a): Conventional water heaters and heat pump water heaters:

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

The water heating energy efficiency is calculated as follows:
η wh = Q ref Q fuel + CC × Q elec 1 − SCF × smart + Q cor
For water-/brine-to-water heat pump water heaters, the electricity consumption of one or more ground water pumps shall be taken into account.

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Source: https://www.legislation.gov.uk/eur/2013/812/annex/VIII/division/3/division/a (the official version)
Page: https://openlegislation.uk/eu-regulation-2013-812/annex-VIII/division-3/division-a
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.