Alcoa has restarted half the capacity at its aluminium smelter in Australia's Victoria that was crippled by a state-wide blackout six months ago.

The Portland smelter has been running at a third of its 300 000 t/y capacity since a freak storm prompted the power outage in December, causing molten aluminium to solidify in the facility's potlines and freezing production.

"Getting to the half way point in our bid to restore the business has been a big task, but what I have seen up to now gives me great confidence in our ability to deliver the plan," Plant Manager Peter Chellis said in a statement.

The plant's resumption has come in part due to a A$240-million ($182-million) government-sponsored rescue package that has secured its future for at least four years in a state that has suffered from a spate of job losses including the shutdown of three major car makers and a power station.

With local power costs soaring, a cheap source of energy was also needed. The Portland smelter lined up a four-year power supply deal with AGL Energy for 510 megawatts, or about 10% of the state's electricity load, earlier this year.

"We are expecting to have production restored to pre-outage levels by early to mid-August," Alcoa spokeswoman Jodie Read told Reuters.

The government's financial aid is dependent on the smelter staying open at least until 2021 and output remaining at least 90% of pre-blackout levels.

The plant is co-owned by Alcoa, Australian firm Alumina Ltd, China's CITIC Resources and an arm of Japan's Marubeni Corp.