Origin Energy has emerged as the big winner in the NSW government's privatisation of the state's electricity.

The company has acquired more than 800,000 customers from Integral Energy and Country Energy and the right to trade the output of the Eraring power station on the Central Coast, News Ltd reports.

TRUenergy is set to take over EnergyAustralia, the largest energy retailer in the state, and the right to trade the output generated by Delta Electricity power stations west of Sydney.

The NSW government is set to make $5 billion out of the transaction, which could be announced on Tuesday.

The reported $5 billion proceeds from the sale would be only a fraction of the $15 billion projected in 2007 when the Iemma government proposed a full sale of the generators, a sale which was thwarted by the unions and the state opposition.