An extension of the scheme from 2027 to 2037 was declared on 1 April 2010 and is detailed in the National Renewable Energy Action Plan.
Where suppliers do not have sufficient ROCs to cover their obligation, a payment is made into the buy-out fund.
ROCs are issued by Ofgem to accredited renewable generators (or in the case of generating stations subject to a NFFO (non-fossil fuels obligation), Scottish Renewables Obligation or Northern Ireland NFFO contract, to the nominated electricity supplier).
Normally, a renewable generator will transfer the related ROCs through Ofgem's electronic registry when it sells power to an electricity supplier.
Some renewable sources of electricity are not eligible for ROCs (e.g. larger hydroelectric schemes which were in operation before April 2002).
When it was first introduced in 2002, each form of renewable energy technology received the same level of support, namely one ROC/MWh of electricity generated.
[22] As a result, whilst being ostensibly technology-neutral, the Renewables Obligation in its original form in fact favoured the deployment of the more established, near-market technologies such as landfill gas and onshore wind, those which were most economically efficient, over less well developed technologies that were further from commercial viability.
A significant contribution would therefore be required from less mature technologies which lacked sufficient incentive to develop into feasible alternatives under the original scheme.
Banding was introduced in 2009 to provide differing levels of support to groups of technologies depending upon their relative maturity, development cost and associated risk.
These bands include a reduction in the tariff for onshore wind to 0.9 ROCs/MWh and an increase for small wave and tidal stream projects, under 30 MW, to 5 ROCs/MWh.
The British Wind Energy Association, whose members are major beneficiaries of the existing scheme, claims that Ofgem is partly responsible for the costs because it has failed to prioritise work on the National Grid which would allow more renewable capacity to be connected.
[30] The Scottish Wind Assessment Project has criticised the scheme for rewarding reductions in renewable electricity output: two electricity suppliers, Scottish and Southern Energy and Npower, down-rated several large hydro-power stations in order to qualify for Renewables Obligation Certificates.
Other than with respect to large scale (>5MW) solar photovoltaic power projects and onshore wind power projects, the Renewables Obligation remained open to new generation until 31 March 2017, allowing new renewable generation that comes online between 2014 (when it was anticipated the CfDs would start) and 2017 to choose between CfDs and ROCs.
However, the UK government subsequently announced that it would bring forward the deadline for Renewables Obligation accreditation for large scale (>5MW) solar photovoltaic power projects, to 1 April 2015.
[33] The government further announced on 18 June 2015 that it intended to close the Renewables Obligation to new onshore wind power projects on 1 April 2016, bringing the deadline forward by one year.
[4] A series of grace periods were set out, where generating stations could be accredited after the closure date, subject to meeting the following criteria.