To ask the Secretary of State for Business, Energy and Industrial Strategy, with reference to his Department's BEIS Electricity Generation Costs (2020) published on 24 August 2020, what estimated value for the annual decline in performance of offshore wind was used in that report.
This answer is the replacement for a previous holding answer.
12 January 2021
BEIS estimates a constant load factor and availability across the lifetime of an offshore wind farm, and therefore a constant performance. This is based on research performed by Arup (2016) and independently peer-reviewed by Professor Derek Bunn (2020).
BEIS also assume an improvement in load factors in future as turbines deployed in wind farms increase in size, and this relationship is discussed in detail in a published study performed by DNV GL (2019).
 ‘Arup (2016): Review of Renewable Electricity Generation Cost and Technical Assumptions’ https://www.gov.uk/government/publications/arup-2016-review-of-renewable-electricity-generation-cost-and-technical-assumptions
 ‘Peer review of 2019 electricity generation cost updates’ https://www.gov.uk/government/publications/peer-review-of-2019-electricity-generation-cost-updates
 ‘Potential to improve load factor of offshore wind farms in the UK to 2035’ https://www.gov.uk/government/publications/potential-to-improve-load-factor-of-offshore-wind-farms-in-the-uk-to-2035