Brown coal power plants believe they are ready for the long weekend's high temperatures, as energy authorities prepare for a grid stretched to the limit.

A heatwave forecast to hit Victoria, South Australia and Tasmania on the weekend has sparked an Australian Energy Market Operator warning that the system will be under pressure.

Similar heat last week, coupled with a number of brown coal-fired power station failures, saw energy prices in Victoria spike to $12,931 a megawatt hour.

Alinta Energy, which recently acquired the Loy Yang B brown coal-fired power station, is positive on its performance ahead of the warmer weather noting it was designed to run ''in extreme conditions".

“Both units are currently operating and are expected to be fully available during the upcoming weekend hot spell and into the summer period,” an Alinta spokeswoman told Fairfax Media.