AUSTRALIA'S highest-emitting brown coal electricity generators are between $400 million and $1 billion better off than they would have been if there were no carbon tax, new modelling shows.

The brown coal generators' stronger-than-expected financial position yesterday forced the Gillard government to abandon its attempts to pay some of them to close down by 2020, infuriating environmental groups and the Greens.

Giving up on the negotiations frees at least $1 billion in the budget from 2013-14.

It triggered demands from the Greens that the government reconsider $4.5 billion worth of compensation yet to be paid to the companies on top of $1 billion already handed over.