Authorities say large parts of the Top End lost power on Wednesday because of a problem with the generator on Channel Island, forcing hospitals onto emergency back-up power and triggering major traffic problems at peak hour.
Shortly after 4:00pm, Power and Water Corporation said its crews were responding to widespread power outages affecting Darwin and the surrounding areas.
The outage affected Darwin city and its surrounding suburbs, as well as Palmerston, Berry Springs, Katherine and the Cox Peninsula.
Outages were also reported at the southern end of the grid more than 300 kilometres south in Katherine.
Both Royal Darwin Hospital and Katherine District Hospital switched to generator power and the NT Health Department told the ABC power was stable at both sites.
Shortly before 6:00pm a Power and Water spokeswoman said the utility had started restoration and had been able to bring some customers back online.
"It is progressive and it's a slow process so that the system can handle it without destabilising it further," the spokeswoman said.
The spokeswoman said the problem stemmed from a gas supply issue at Channel Island which had been resolved.
Stores including Darwin's Nightcliff Woolworths supermarket had temporarily closed, while Territorians were forced to swelter without working air conditioners in more than 33 degree Celsius temperatures.
Northern Territory police reported 34 traffic lights out between Darwin and Katherine at around 4.30pm.
Watch commander Andrew Heath said police were organising extra officers to direct traffic at intersections.
"We understand it's peak hour traffic and everyone wants to get home — we are asking people to be patient and tolerant," he said in a message to ABC Darwin radio.
"Give way to the right at uncontrolled intersections."
