NSW Treasurer Mike Baird announced the sale of Eraring Energy to Origin Energy on Monday,saying it was"above retention value".
Under the deal,which is expected to be completed by August 1,the government has agreed to pay Origin $300 million compensation for the right to break a contract guaranteeing Eraring cheap coal supplied from the Cobbora mine.
The contract was signed as part of the previous government's sale of electricity trading rights,which saw Eraring's electricity output sold to Origin shortly before the 2011 state election.
As part of that sale,Eraring was guaranteed cheap coal supplied by the planned Cobbora mine,which was to be built by the state government,in an attempt to boost the value of its generation rights.
But a recent review of the Cobbora deal by the former Treasury official Kerry Schott found Cobbora would cost"at least"$1.4 billion to develop - money that would never be recovered by the sale of its coal because the contracted supply prices were"well below cost".
Dr Schott is advising the O'Farrell government on its sale of the state-owned generation companies Eraring Energy,Macquarie Generation and Delta Electricity,from which it anticipates proceeds of up to $3 billion.
Mr Baird said the former government's sale - known as the GenTrader transaction - was"a shocker".