Twenty-five Coalition lower house MPs have signed a petition asking for the aluminium smelting industry to be exempt from the Renewable Energy Target (RET).

As one of the single largest users of electricity in the country, aluminium smelters say the RET conditions will cost the industry $80 million a year by 2017.

Some say the target - designed to push Australia to draw 20 per cent of its electricity from renewable sources by 2020 – has already pushed two smelters out of the game.

The Kurri Kurri smelter in New South Wales was mothballed by owners Norsk Hydro in 2012, and Alcoa has announced it will close the Point Henry smelter in August.

Industry figures say aluminium smelting should be treated as a special case, because its energy demands are so high.

Current figures say a smelter in Tasmania uses about 25 per cent of the entire state’s electricity, and in Victoria roughly10 per cent of all energy goes to smelting.

More than a quarter of the Federal Government's backbench signed the letter over the weekend, and it has now been sent to Industry Minister Ian Macfarlane and Environment Minister Greg Hunt.

Meanwhile, falling energy demand suggests Australia may even exceed its 2020 target.

Origin Energy says its figures show Australia will be drawing 27 per cent of its energy from renewable sources by then.

Reports say modelling by the aluminium industry shows Australia could meet its 2020 target, while also granting a 100 per cent exemption from RET for smelting.