The Australian Energy Regulator says ActewAGL can run more efficiently, like Victoria's and South Australia's, which Mr Costello rejects.

He still refuses to disclose his remuneration, which came under scrutiny in 2013 after it emerged ACTEW's then managing director Mark Sullivan's pay packet had been under-reported by $234,000.

"My remuneration will drop as a result of this, I have already made the decision, by probably about 40 per cent. I'm going to be hit by this, that's what I put my hand up for," Mr Costello said. Other executives' pay would be cut, too.

"If I were paid zero it would make no difference to what's happening now. This [regulator's proposal] is such a gigantic cut my wage or my executives' wage is a bagatelle in the whole thing."

Electrical Trade Union assistant secretary Neville Betts wasn't moved by Mr Costello's gesture. "If you can take a 40 per cent cut and still do pretty well, something's wrong," he said.

Mr Betts reckons Mr Costello's pay is about $1 million. He says if the regulator has found room for cuts, the excess is of management's making.

In a newsletter to members Mr Betts says executives will not tell the workforce what they are sucking out of the organisation in pay and bonuses. "That's where savings should start, at the top and work down," he said.

ACT taxpayers own half of ActewAGL, represented by two shareholders, Chief Minister Katy Gallagher or Treasurer Andrew Barr.

The ETU suggests the shareholders should take a smaller dividend, not their hard-working members who kept the power flowing to the community.

Mr Betts estimates 20 per cent of the ACT workforce could lose their jobs, and following a recent restructure involving redundancies, cannot see where the potential is for such cuts.

Mr Betts said the regulator's office was run by economists putting their effort into identifying cuts with no regard for legal contracts such as enterprise agreements and contractors' obligations, which was ridiculous.