The RO requires electricity retailers to source a rising proportion of their power from renewables by buying renewables obligation certificates (ROCs) or by paying a penalty to "buy out" all or part of their obligation. One ROC is equivalent to one megawatt hour of electricity (Windpower Monthly, October 2009)
In 2008-9, the RO stood at 9.1% in England, Wales and Scotland, and 3% in Northern Ireland. In previous years, the gap between the number of ROCs and the level of the obligation has steadily widened. However, according to the Renewables Obligation Annual Report 2008-9 produced by regulator Ofgem, renewables generators have closed the gap slightly, with the proportion of the obligation met by ROCs increasing by 1% to 65%.
Onshore wind's share of renewable generation has been steadily increasing and for the second year running was the leading renewables technology - accounting for 33% of all ROCs. Taken together, onshore and offshore wind supplied 40% of total renewable generation. The stronger wind resource for offshore meant that, for the first time, the number of ROCs issued for offshore wind exceeded those for onshore wind.
In future this trend will continue as the volume of new offshore wind capacity rises - and because from April 1, 2009, offshore wind receives increased support of 1.5 ROCs for each MWh. This will rise to 2 ROCs/MWh for a handful of wind farms in future years.