The Department for Energy and Climate Change (DECC) does not use any one, single load factor assumption for onshore wind. Load factors may vary according to prevailing site conditions and technology used.
Analysis for DECC by Redpoint/Trilemma (2009)1 used load factors for onshore wind of 21 per cent (low), 27 per cent (medium) and 29 per cent (high). The Digest of UK Energy Statistics 2009 reports that average onshore wind load factors have varied between 26.7 per cent and 29.4 per cent over the period 2004 to 2008 (unchanged configuration basis).
1 Redpoint/Trilemma, 2009, Implementation of the EU 2020 Renewables Target in the UK: RO Reform