Businesses in the Invercargill CBD were without power for an hour this morning after a cable failure resulted in a power outage.

The outage occurred at approximately 10.31am, cutting power in the CBD as well as Bond and Mersey Streets.

According to PowerNet chief executive Jason Franklin, power supply was lost to 840 customers for up to 60 minutes.

Supply was restored to 739 customers by 11.01am, and the remaining 101 customers by 11.31am. 

"We are aware of the importance of power supply to our customers and thank them for their patience during the outage," Mr Franklin said. "The safety and well-being of our employees and the community are our first priorities when working on restoring electricity the networks we manage."

He said PowerNet were currently working on determining the cause of the outage, which affected two Electricity Invercargill Ltd feeders.