New Zealand's hydro lakes at record levels heading into winter, but challenges remain

Throughout summer we saw the impact record rainfall can have and we are still seeing it in our lakes.

New Zealand's hydro lakes are at record levels as we head into the cooler months and one power company says it will be the most renewable winter yet. But that doesn't mean the grid won't face challenges.

Lake Pukaki - a jewel in the Mackenzie Basin's crown. And also one of New Zealand's hydro lakes that's full to the brim.

"They're at record high levels going into winter," said Transpower CEO Alison Andrew.

It's the result of record-high summer rainfall.

"This winter I believe will be one of our most renewable winters yet in terms of our electricity generation," said Meridian Energy general manager wholesale Chris Ewers.

That's safeguarding New Zealand from the dreaded dry winter.

"We have a lot of water in our system which is great for our hydro generators, we've got good geothermal resources and we have wind on top," Andrew said.

This means lower power prices but households won't necessarily feel the difference.

"For most residential households out there their prices are fixed so this will have no impact on the price they pay during the winter," Ewers said.

While we have lots of hydro generation, we don't need thermal plants to run. However, that can be problematic because they can take up to 24 hours to warm up - hardly a quick fix on those days when we all need electricity in a hurry.

The grid has faced five power emergencies over the past two years.

"We carry a residual in the system to manage the uncertainty of extra demand peaking or the wind falling away when those margins get squeezed and if you don't have that thermal plant you can't call on that," Andrew said.

Electrification has increased significantly and so has peak demand.

"From a wholesale price point of view we see large periods of low prices except for when we do get into peak demand periods, typically between 5pm to 7pm at night, and then we see prices lift which requires more generation," Ewers said.

That could eventually come from a backup battery like the Lake Onslow pumped hydro scheme the Government is currently investigating.

As New Zealand transitions to El Niño, we can expect a colder winter and drier temperatures.

"Working really hard to make sure we don't have power outages going into winter," Andrew said.

We will need it to warm our homes this winter.