The sale is due for settlement in February 2012 under the terms of the voluntary agreement that was recorded on May 13.

The market price of $19 a tonne was determined after AGL commissioned law firm Minter Ellison to design the documentation around which emissions units will be traded. A range of different ETS design scenarios was taken into account when developing the documentation.

Starting trade now would allow for a smooth start to trading when the ETS is in operation, according to AGL.

It would also be of benefit to major customers who wish to lock in retail energy prices now and could enable additional liquidity to be set aside for forward electricity contracts beyond July 2010.