©istockphoto/Sarah Skiba

A POWER outage in the Hunter Valley has been felt across five Australian states, cutting power to at least 200,000 customers.

Australian Energy Market Operator (AEMO) spokesman Paul Bird said customers in Queensland, NSW, South Australia, Victoria, Tasmania and ACT had been affected by the blackout.

A generation problem at the Bayswater power station in the Hunter Valley around 11am (AEST) caused parts of the electricity grid to shut down, Energy Australia confirmed.

"NSW... lost a large amount of load suddenly," Mr Bird told AAP.

About 100,000 customers in NSW have been affected, while 50,000 households in Queensland were without power on Thursday.

In Tasmania, the problem had only affected industrial customers, he said.

Victoria was affected to a lesser degree, with 105 sets of traffic lights in southeast Melbourne believed to be linked to the outage.

An Energy Australia spokeswoman said 60,000 Energy Australia customers on the Central Coast and in Sydney's inner west were without power for around half an hour.

"We've received the all clear to restore power to those areas, which we've done," the spokeswoman said.

"The majority of areas have their power restored now."

Integral Energy said 27,000 of their customers were affected, mostly around Wollongong and Shellharbour and across western Sydney.

A spokeswoman said engineers would begin restoring electricity about noon.