Meridian Energy has taken delivery of a new 108-tonne transformer for its Manapōuri power station, which will help take the New Zealand’s biggest hydro station back towards maximum capacity.

The transformer had to travel from Bluff to Supply Bay, where it was barged across Lake Manapōuri to the station and reversed down a 2km tunnel.

Manapōuri has been operating at reduced capacity for around two years now, so the new transformer will bump it back towards its maximum capacity, Meridian said.

A further replacement transformer is expected to arrive at Manapōuri late next year.

The Manapōuri transformers have been a challenge for business since 2011, so the company will also buy a spare, chief executive Neal Barclay said at the company’s latest annual result.

“But with global demand for transformers high, that spare and the transformer for the seventh unit aren’t expected until September 2025. And then we’ll need 12 weeks for installation and commissioning,” he said.

The new transformer is expected to be installed well before Christmas.

Manapōuri lies within Fiordland National Park.

The power station has seven 128-megawatt generating units, and an operating maximum station output of 800 megawatts.

Manapōuri generates enough electricity for about 619,000 average homes, according to the company’s website.

The station is on the edge of Lake Manapōuri’s West Arm.

Its generating units are housed in a cavern excavated from rock 200 metres below the lake’s surface.

Jamie Gray is an Auckland-based journalist, covering the financial markets and the primary sector. He joined the Herald in 2011.