They occurred as the island grows more dependent on solar energy. But the previous blackouts, in 2015, were caused by fossil-fuel plants.

The rolling blackouts that swept across Oahu on Monday night were caused by a chain of storm-related events that all occurred around the same time, according to Hawaiian Electric.

First, there were the heavy rains that flooded one of the eight power-generating units at the company’s Waiau plant and damaged another unit there, knocking out 100 megawatts of the oil-fired electricity produced at that Central Oahu facility, spokesman Darren Pai said. 

At the same time, cloudy skies deprived the island of the solar energy it has increasingly come to rely on in recent years. That caused key battery facilities in Kapolei and Waiawa, which combined can store nearly 1,000 megawatt hours of power, to run well short of their storage capacity during the storm, Pai said. 

HEI HECO Waiau power plant outside1. 14 april 2016.
Flooding at Hawaiian Electric’s oil-fired power plant in Waiau was one of the factors that led to rolling blackouts across Oahu Monday. (Cory Lum/Civil Beat/2016)

Those factors prompted Hawaiian Electric to publicly announce Monday that, for the first time in almost exactly nine years, rolling blackouts might have to occur on Oahu starting at 5:30 p.m. Customers responded by reducing their power use, ensuring that the blackouts didn’t need to start at that time, Pai said.

Instead, they started at 8 p.m. after the storms caused more of the island’s power sources to drop off at the H-Power waste-to-energy plant in West Oahu and at windfarms on the North Shore. How exactly the storms affected H-Power are still being investigated, Pai added.

The 30-minute rolling blackouts, which covered most of the island, raised renewed concerns by some residents over state leaders’ decision to close Oahu’s last remaining coal-fired plant in 2022 even though Hawaiian Electric had failed to bring online all the renewable projects needed to replace it.

On Wednesday, Pai noted that the 180-megawatt coal-fired plant operated by AES had not prevented rolling blackouts from occurring on Oahu in the past when it was still operating. 

The AES plant helped cause the previous blackouts in January 2015 when it tripped offline along with several other fossil-fuel-powered plants, he said.

“It’s not about how the energy is generated,” he said of rolling blackouts’ cause. “What we had here were impacts to a number of different parts of the generation system all at the same time, and that’s what put us in this situation.”

Still, local regulators have previously taken Hawaiian Electric officials to task for not having sufficient renewable energy projects ready to replace the AES plant. 

The decision to close the state’s last coal-fired plant in West Oahu before sufficient renewable power sources had been built to replace it generated concerns among the island’s ratepayers. (David Croxford/Civil Beat/2023)

“Those projects were going to smooth the transition,” former Hawaii Public Utilities Commission Chair Jay Griffin said during one of the group’s public meetings in 2021. “We’ve lost a year and they’re now pushed out. So who’s going to bear that cost? Is Hawaiian Electric going to bear that cost? Why does the public have to bear it?”

Hawaiian Electric has a Renewable Energy Projects status board on its website with updates on when the public can expect more power to launch in the coming years. 

The company has also used a “Battery Bonus” program that allows customers to sell some of the power they generate with their rooftop solar panels back to Hawaiian Electric for use on the grid, making up at least some of what it lost from the AES plant’s closure.

In December, the company announced it was advancing with contract negotiations for seven of those projects on Oahu. They consist of three solar-and-storage projects and four biofuel projects, to generate nearly 600 megawatts of what’s known as “firm” power for the island, according to a company release

“It gives us more tools to work with to help balance out the generation so we can meet the needs of our customers,” Pai said Wednesday.

The company has not released an estimated date or year for when it expects renewable energy sources to completely offset what was being generated at AES. On Tuesday, it announced that the rolling blackouts would not be needed that night.

Some of Oahu’s industrial areas, such as Campbell Industrial Park in West Oahu, were spared from the blackouts because they don’t use the same amount of electricity during peak hours as residential areas, Pai said.

Hawaiian Electric also took into account areas with hospitals and other facilities critical to public health and safety when deciding the blackout schedule, Pai added. The 30-minute intervals helped to ensure those facilities would have sufficient backup power to keep running, he said.

Those efforts to keep critical facilities afloat during rolling blackouts are separate from the company’s more recent efforts to finally develop a power safety shutoff program and cut the electricity in vulnerable regions ahead of a wildfire or other emergency.

Hawaiian Electric received widespread criticism for not having such a plan in place ahead of the Lahaina wildfires in August.

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