As the giant Hazelwood coal plant turns off the last of its units, the national electricity grid manager has sought to reassure the public it is taking steps to ensure the lights stay on when demand soars next summer.

In an interview with Fairfax Media, the Australian Energy Market Operator [AEMO] said Hazelwood's closure would be offset by the availability of three mothballed gas-fired stations – one each in South Australia, Tasmania and Queensland – and large industrial businesses agreeing to time-shift their electricity use in the event of an emergency.

"The risk is no greater than it was this summer when you look at the generation that's available to us," AEMO chief operating officer Mike Cleary said.

Hazelwood's owners have gradually shut off its eight generation units this week ahead of its closure on Friday.