The $16 billion privatisation of electricity company Ausgrid will be examined by the NSW Auditor-General amid questions about the "unsolicited proposals" process used by the successful bidder.

Last October then Premier Mike Baird announced that Australian Super and IFM investors would pay $16.189 billion for 50.4 per cent of Ausgrid on a 99-year lease after an unsolicited proposal to the NSW government.

The proposal was first revealed in late September, shortly after Chinese bids for the original tender were blocked on national security grounds by federal Treasurer Scott Morrison.

The unsolicited proposal rules allow for a confidential approach to the NSW government with a unique proposition that, if accepted, does not need to go to tender.