British electricity market regulator Ofgem is revising its guidelines for supplying power from renewables to ensure that customers opting for a green supply can be sure they are making a difference. The guidelines need revising because of new developments in the UK renewables market, says Ofgem. It points out that the Energy Saving Trust's Future Energy accreditation of green power has been discontinued, superseded by Renewable Energy Guarantees of Origin (REGOs) certificates, the industry now has two years experience of the Renewables Obligation and, more recently, electricity retailers are now required to disclose the fuels used to generate electricity. Under Ofgem's proposals for the new guidelines, electricity suppliers will have to state what technologies are used to generate renewable power. Customers need to be confident that they are contributing to renewables development over and above the legal obligations on suppliers to buy renewables, says Ofgem.