More than 7000 homes and businesses in Tokoroa were without electricity on Thursday morning.
The unplanned outage at 9.21am was caused by lines coming down on Baird Road, with 7041 customers affected.
Lines company Powerco said it was still investigating the cause.
“Customers were progressively restored, with all customers except one reconnected by 10am,” Powerco said in a statement.
“Field crews are on site carrying out repairs and the remaining customer is expected to be reconnected this afternoon.”