Hamilton lines company WEL Networks has launched the country's first utility-scale battery storage system.
The battery, which is near Huntly, can provide 35-megawatt-hours of energy - enough for about 2000 homes - and is capable of providing `fast reserves support' for the national grid in the North Island.
The build of the site began in July last year, and there've been delays that meant it took a year longer to complete than originally planned.
The lines company has set up a subsidiary - NewPower Energy - which will own and operate the battery, selling generation into the electricity reserves market.