The Commerce Commission says Auckland lines company Vector has been issued with a $1.1 million fine.
Vector was taken to court by the commission late last year - for the second time in four years - for having too many power outages.
The commission said Vector had breached "network quality standards - relating to excessive power outages from 2017 to 2020".
Vector's failures affected a large number of consumers and businesses, the commission said.
"Auckland consumers have the right to expect a good quality of service from their lines company and Vector did not implement measures to deal with its network reliability as early as it should have," associate Commerce Commissioner Vhari McWha said.
Vector's penalty was discounted by 36 percent due to its cooperation with the commission's investigation, with the total fine imposed being $1,158,400.
In a statement, Vector Group said it was pleased the breaches were now resolved.
"Our ongoing focus on improving reliability has seen us comply for the 2021 and 2022 regulatory years," chief executive Simon Mackenzie said. "This reflects a huge and continued effort by our staff and our field service providers to manage the challenges of Auckland’s significant growth, whilst also investing in network reliability and performance."