8PM UPDATE: An Endeavour Energy spokeswoman says power has now been restored to the majority of homes in Barrack Heights and Shellharbour.
"We're down to 200 homes without power now, as crews switch people over the another sub station," the spokeswoman said.
It is anticipated the remaining homes will have powered restored within the next 30 minutes to an hour.
Workers will continue to investigate the cause of the outage.
7.13pm: Parts of Barrack Heights and Shellharbour are without power this evening.
Endeavour Energy said it has urgently dispatched crews to the area in a bid to restore electricity to more than 1000 homes.
The company has a full list of affected areas and streets on its website, including The Kingsway, where 48 homes are without power, Loftus Drive (72 homes), Sammat Avenue (61), Cassia Street (75) and Strate Avenue (76).
Endeavour has estimated it will take three hours to fix the problem, telling customers they can expect power to come back on by 10 o’clock this evening.