The phase 2 delays led the Government to introduce a transitional alternative support mechanism, the Renewable Heat Premium Payment (RHPP), which provided a subsidy for the installation of new domestic systems via a one off payment. The aim was to reduce the cost of purchase of new systems and ensure that domestic demand was not totally disincentivised in the ALW-II-41-27 up to the introduction of phase two. The RHPP was initially limited to support for a maximum of 25,000 systems with a budget of £12 m made available from August 2011 to March 2012, though this was underspent by £4.5 m. The delays to the domestic RHI meant the RHPP was extended to March 2013, with additional expenditure of £7 m and again until March 31st 2014  with the additional total of approximately £12 m. RHPP Payments are specifically linked to the recipient making data on energy output from installed systems available to DECC for aggregation, which will inform further policy development. This codicil can be regarded as potentially offering substantial benefit in an area where little operational data is available and can be regarded as an example of good practice for future policy design . (The need to gather good data is further recognised with domestic RHI payments for those who install appropriate metering technology of £230 per year heat pumps and £200 per year for biomass boilers ).