A wave energy generator which was launched off the New South Wales south coast in March, has sunk in rough seas.

The 170-tonne structure had been providing electricity to the grid from 150 metres offshore at Port Kembla.

But it broke free from its pylons on Friday afternoon and sank on Saturday.

Early efforts to tow the barge to safety were abandoned due to the rough conditions.

The Chief Executive Officer of the Port Kembla Ports Corporation, Dom Figliomeni, says the structure was battered against the break water.

He says attempts to retrieve the barge will be made this week.

"There's been no impact on the provision of services to shipping and where it is at the moment it's not a navigation hazard," he said.

"We will continue to monitor its location."

The generator's Sydney-based developer, Oceanlinx is investigating what happened.