Alinta Energy says its coal-fired power stations at Port Augusta in South Australia will close in early 2018, or possibly sooner.

Alinta’s Northern and Playford B power stations will close along with the mine that supplies them; Leigh Creek coal mine.

The company says they will not run after March 2018, but could close even sooner.

It said the closures were inevitable, as operations had become “increasingly uneconomic”.

The Australian Energy Market Operator says the Northern Power Station has been operating at 50 per cent capacity for the past year, while Playford B plant has been offline entirely.

Alinta is reporting operating losses of about $100 million from the last four years, while it has also invested another $200 million to extend its operating life.

Alinta Energy CEO Jeff Dimery has told reporters that 438 workers will lose their jobs; 258 at Leigh Creek and 180 at Port Augusta.

Workers reportedly found out through the media, but say company management have since been spoken to them as well.

Mr Dimery said a number of factors could see the sites close sooner, such as the performance of the plant and potential workplace safety issues.

The announcement came just days after two firefighters and a worker were injured by an explosion at the plant.

Mr Dimery says there has been a decline in energy demand in SA, as big industrial customers fall and household efficiency increases.

Alinta says it will work with the SA Government, unions and communities to ease the pain of the changes.

South Australian Premier Jay Weatherill says the Government will provide an initial $1 million in support for the communities most affected by the closures.