Two operations were disrupted when a software failure left part of the Royal Adelaide Hospital without power for up to 20 minutes yesterday morning.

SA Health said early advice indicated there were no adverse patient outcomes and no emergency surgeries were affected.

It said maintenance crews were testing a generator and the power outage happened because a software failure prevented the affected section of the hospital from being switched back from generator to mains power.

SA Health said that it was examining the software to work out what went wrong.

Associate Professor William Tam was in the "middle of a quite complex procedure" on a 97-year-old patient when the power cut out for what he estimated to be about 20 minutes.

"The anaesthetic machines still had access to power, but I was totally in the dark without any information about what was happening to my instrument which was still inside the patient," Professor Tam said.

"I think it was a distressing and disturbing to everyone and I mean the anaesthetist, I mean the doctors, I mean the nurses.

"Thank goodness there was a degree of calm amongst the team. We kept thinking the generator would kick back in, it didn't and we had to make the call to ... complete the procedure as quickly as we can."

Professor Tam said that fortunately, there was no harm to his patient but said that did not mean what happened was acceptable.

He said doctors and patients must be able to have confidence the new hospital is safe.

"We all have been working with SA Health to fix some issues and we appreciate new buildings need some tweaking," he said.

"But power reliability is a non-negotiable function."

The Australian Medical Association has called on SA Health to address the reliability of power "as a matter of extreme urgency".

Health Minister Peter Malinauskas said the clinicians did an outstanding job at improvising under the circumstances, which he described as "less than ideal".

Hospital generator failures caused problems during SA's statewide 2016 blackout. ( ABC News: Tony Hill )

In 2016, embryos being prepared for transfer at a fertility clinic had to be destroyed due to a generator failure at Flinders Medical Centre during a blackout which hit the whole of South Australia.

Twelve patients were affected by the tragedy when back-up generators stopped an hour after automatically kicking in.

The then-health minister Jack Snelling said the generator had been checked in preparation for the storm, but a fuel pump had failed on the day.

A later review found the generator failure was "likely caused by human error in wrongly leaving a control switch off" and there was a "lack of alarms to notify maintenance staff of an impending shutdown due to a low fuel situation".

Port Augusta Hospital was also left without power due to its generator failing several times within a 24-hour period.

A separate report into that failure found the hospital was without power for about five hours due to the 44-year-old generator overheating, having an oil leak, a split rubber hose and unsuitable batteries installed.