South Island power consumption has decreased by 8% compared with the corresponding period last year due, in part, to the nationwide lockdown.

Contact Energy spokeswoman Leah Chamberlain-Gunn said while households were staying at home and using more electricity during the Alert Level 4 lockdown, much lower activity in the industrial sector had resulted in an overall reduction in demand.

“Nationwide consumption reduces during lockdown as industrial processes stop and commercial business turn their lights off,” she said.

Despite the decrease, the company was still carefully managing South Island power generation, due to an unplanned high voltage direct-current (HVDC) cable outage earlier last month.

The cable route of electricity supply to the North Island State Highway 7 in North Canterbury.

It was repaired last week after high winds previously affected Transpower’s ability to complete the repair.

The outage reduced the cable’s capacity by up to 50% during peak periods, affecting every South Island generator’s ability to get electricity from the South Island to the North Island, Ms Chamberlain-Gunn said.

With transmission to the North Island limited and snow melt increasing due to warmer weather than usual in the lockdown period, Contact had more water than necessary for current demand but little ability to store it.

As a result, the company opened the Clyde Dam spill gates last week.

The dam was part of the “run of river” Clutha scheme with minimal storage capacity.