UK electricity retailers reported an average shortfall of 34% for 2006/07 in meeting their renewables obligation (RO) from purchases of electricity from renewables. The RO requires all electricity retailers to secure a rising proportion of their power from renewable sources. In 2006-07 the level of the RO stood at 6.7% in England, Wales and Scotland, and 2.6% in Northern Ireland. Retailers meet their obligation by buying Renewables Obligation Certificates (ROCs) or paying a "buy out" penalty of £33.24 per ROC to cover any shortfall. At present, one ROC is equivalent to one megawatt hour. According to figures for the year released by energy regulator Ofgem, only 66% of retailers met their obligations through purchases of ROCs. Retailers submitted a total of 12,868,408 ROCs compared with the total obligation for the year of 19.4 million MWh. In its Renewables Obligation Annual Report for 2006-07, Ofgem explains that one reason for the shortfall was the reduction in the percentage allowed to be met by ROCs from co-fired biomass. Of the major retailers, only ScottishPower, now a subsidiary of Iberdrola, managed to meet its obligation entirely from ROCs. EDF Energy, however, came close by meeting 98% of its obligation from ROCs. By technology, landfill gas was just marginally ahead of onshore wind in the amount of electricity generated -- each with a 28% share of the renewables total. With the number of new landfill sites declining, however, onshore wind is set to top the league table this year. Offshore wind held a 5% share.