The gap between the volume of green power that electricity retailers are required to buy under the Renewables Obligation (RO) and the amount of electricity available from green sources has widened, the latest annual report on the RO reveals. It is published by electricity regulator Ofgem. In its second year from April 2003 to March 2004, the RO required electricity suppliers to submit Renewables Obligation Certificates (ROCs) covering 4.3% of their sales. The annual report, however, shows that purchases of ROCs -- and SROCs in Scotland -- covered only 56% of the country's total obligation, a shortfall of 44%. This compares with a shortfall of 41% in 2002-03. Over 7.5 million ROCs and SROCs were issued to green generators over the year, representing a 35% increase in renewable generation over the previous year. But the rise in the number of ROCs available was not enough to compensate for the increase in the obligation on each supplier from 3% in 2002-03 to 4.3% in 2003-04. A total 616 generating stations were accredited. The dominant renewable technology was landfill gas, which supplied almost 42% of ROCs. Onshore wind contributed 16%. Ten retailers met 100% of their obligations through producing ROCs, but of the country's major suppliers, only ScottishPower and Centrica subsidiary British Gas were wholly compliant. The other 30 had to cover their shortfall by paying a penalty to "buy-out" part or all of their obligations. In the current year, 2004-05, the level of the RO stands at 4.9%.