Kiwis are being warned to reduce their electricity use on Wednesday evening amid "potential tightness" in supply.
Electric Kiwi emailed its customers with advice on how to save power, saying it was running a trial to reduce energy use.
"The grid is facing potential tightness of electricity supply tonight from 6pm-7:30pm," the email said.
"As winter announces its arrival with chilly evenings across the country, electricity generators have to ramp up supply to meet the increasing demand. It's a great reminder to be mindful of our electricity usage during the busy evening peaks.
"By reducing your power usage tonight from 6pm-7:30pm, you can help us measure the collective dent we can make by working together to reduce our energy usage during winter peaks.
"This trial will help us prioritise future ways for our customers to participate in peak demand events and save money while you're at it."
Advice to save power included delaying using the washing machine, holding off on charging devices and electric vehicles, and turning off lights and heating in rooms not in use.
"You should stay warm by continuing to heat the rooms you are using. However, where possible, you could consider turning down the thermostat slightly," the email said.
"As a bonus, you'll be reducing your carbon footprint, as carbon emissions from electricity generation tend to be higher during peak demand periods."
Electric Kiwi said it hoped customers would participate in the trial and that it would share the results.
Transpower also put out a notice to Kiwis saying if "the situation worsens, we may have insufficient generation to meet demand and cover reserves for a contingent event".
The warnings come as Genesis Energy announced it would resume importing coal, saying it needed to stockpile 350,000 tonnes of coal due to increased demand and a dwindling gas supply.
Associate Energy and Resources Minister Shane Jones praised the move on AM on Wednesday.
"The gases in the ground sadly have been stigmatised in the last six to seven years, and we are going to rely increasingly on coal because of the uncertainty of gas," he said.
Figures released by an industry body show gas production has dropped by nearly 30 percent so far in 2024, on top of a 12.5 percent drop in production last year.
The figures are concerning for those who rely on gas - such as schools, hospitals, universities, food and chemical processors and electricity generators.
"We are sitting on an enormous amount of gas," Jones said. "We need the investment to extract it, which is why I'm changing the law, to make it a lot more permissive, to enable people to go and extract and look for gas and also reside the burdensome nature of the decommissioning which was imposed on the industry by the last Government."
