Mr O'Grady was leaving for a school run on Friday when the power went out at his inner north home.

Just minutes later, he came upon the accident scene on Boldrewood Street in Turner.

''I was literally driving along and saw this man lying on the road with a couple of people sort of looking down at him,'' Mr O'Grady said.

''I stopped and asked if they needed help [and] they asked me if I knew anything about resuscitation.''

Mr O'Grady got out of the car and began performing CPR on the unconscious truckie, who had been seriously injured when his tip truck came into contact with overhead power lines.

By sheer coincidence, Mr O'Grady, a scout leader, had taught his cub scouts about resuscitation and what to do in an emergency just days before.

''You practise these things and all of a sudden you're the man on the spot and it's all up to you,'' he said.

He said he worked on the man for what seemed like a long time ''but was probably only 10 minutes'' until paramedics arrived.

''The ambulance guys said, 'You're doing a good job - keep going,' which I didn't quite expect, but that let them set up defibrillation and oxygen and all that,'' he said.

The truck driver was transferred to St George Hospital in Kogarah where he remains in the intensive care unit.

A spokeswoman for the hospital said the man's condition was stable.