Waiau Repower

Waiau Repower


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Waiau Repower

About the Project

Hawaiian Electric proposes to install, own and operate six new simple-cycle combustion turbines that will replace the aging oil-fired steam turbines at its Waiau Power Plant facility in Pearl City, Oahu. The project will repower the facility with proven, fuel-flexible and modern technology; serve as a vital backup for variable renewable resources; strengthen resilience; and contribute to Hawaii’s goal of 100% renewable energy by 2045.

Aerial shot of Waiau Power Plant, circa 1950
Waiau Power Plant, circa 1950.


Construction on the Waiau Power Plant began in 1937 as Hawaiian Electric’s second largest power plant to complement the utility’s then existing plant in downtown Honolulu on Alakea Street.

The first two units came online in 1938 and 1940, respectively. Shortly after, on Dec. 7, 1941, came the attack on Pearl Harbor. Although the power plant was hit by machine gun fire from Japanese aircraft, Waiau crews bravely shut down and re-started plant operations several times to minimize potential damage to the equipment.

During World War II, electric power use climbed with the military presence and a growing population which placed a demand on Hawaiian Electric to expand its production.

Construction of a new building to house what would become Waiau Units 3 and 4 began in mid-1945. Unit 3 went into service in 1947 followed by Unit 4 in 1950. By the time Hawaii became the 50th state in 1959, outdoor generating Unit 5 came online and was joined two years later by Unit 6 in the same structure. Unit 7, an outdoor generating unit, became operational in 1966 and was joined in 1968 by Unit 8 in the same structure.

Units 1 and 2 were retired in 1982 after more than 40 years in operation. Units 3-8 have been in service between 76 years for the oldest unit and 55 years for the youngest and are due for retirement. Replacing the older and larger fossil-fueled boilers with efficient modern generation will provide reliable, firm generation that can be rapidly dispatched to supplement variable renewable resources.

News Releases

January 3, 2024 – Hawaiian Electric will share details of its plan to repower the Waiau Power Plant in Pearl City at a community meeting on Tuesday, Jan. 16, from 6:30 p.m. to 8 p.m. at Waiau Elementary School (98-450 Hookanike Street). The meeting also will be streamed live on facebook.com/HawaiianElectric. Read full news release.

December 11, 2023 – Hawaiian Electric’s proposal to replace six aging fossil-fuel generators at its Waiau Power Plant in Pearl City with more efficient, fuel-flexible units has been selected to advance to the next stage of an energy procurement process overseen by the Public Utilities Commission (PUC). Read full news release.

May 18, 2023 – Hawaiian Electric is proposing to replace six aging fossil fuel-powered generators at its Waiau Power Plant in Pearl City with smaller, more efficient and fuel-flexible units that can provide reliable, firm generation to back up the expanding portfolio of variable resources like solar and wind on the Oahu electric grid. Read full news release.

Project Benefits

As Hawaiian Electric transitions to a sustainable, clean energy portfolio, the company must also meet customers’ expectations for continuous, reliable power. The new units will use the same technology employed by aviation or jet turbine engines and can run on biodiesel, diesel and potentially hydrogen. The technology allows for quick start up and shut down, which will result in fewer operating hours compared to the existing steam turbine boilers that the new units will replace. This will lower greenhouse gas emissions, among other benefits.

The Waiau Repowering Project will offer these benefits:

This project will provide firm generation resources available 24/7 to ensure reliable power generation across Oahu.

The Waiau repowering project will replace the aging and larger oil-fired generating units with fuel-flexible, efficient, simple-cycle combustion turbine units that will be capable of using diesel, biodiesel and potentially hydrogen.

Combustion turbines have a better operating efficiency than steam turbine boilers as combustion turbines use less energy for the same amount of electricity output.

Historically, the existing steam turbine boilers at the Waiau Power Plant operated as base load and cycling units. They typically required a few hours to start up and a few hours to shut down. The new units are capable of starting and ramping to full output within 10 minutes. Shut down procedures also take minutes instead of hours. Additionally, anticipated operation of the new units will support customer peak demand periods while helping to stabilize the grid with firm generation.

As a result, it is anticipated that the new units will operate fewer hours with a better efficiency compared to the existing steam turbine boilers they will replace.

The new units are intended to fill the gap when variable renewable generation and storage resources are unavailable or unable to meet the system demand.

A key purpose of the new units is to utilize more generation from other renewable resources such as photovoltaic, wind, hydro, waste-to-energy, biomass, geothermal, etc. The ability of the combustion turbines to quickly react (start up/shut down and ramp up/down) to meet fluctuations in intermittent renewables, such as solar and wind generation, will enable Hawaiian Electric to reduce the curtailment of energy from variable renewable resources while also enabling the increase in the amount of future variable renewable resources on the Oahu electric grid.

By transitioning from the existing fossil fuel generation fleet to a modern generation fleet, it will result in the use of a cleaner fuel source, reduce operating hours and incorporate additional clean, renewable energy resources on the grid. Retiring older units with modern, efficient generation resources also supports Hawaiian Electric’s decarbonization goals to achieve 70% reduction in greenhouse gas emissions from 2005 levels by 2030.

Understanding the importance of land use, Hawaiian Electric proposes to use the existing Waiau Power Plant facility for this project and will not expand the use of land for power generation.

Developing this project on land it already owns allows Hawaiian Electric to utilize existing permitting, zoning, and resources, and eliminates the need for new land acquisition processes or issues. Unlike projects that propose development on land that has never been used or developed before (e.g., greenfield sites), the Hawaiian Electric project will not take away property that could be used for other purposes.

Hawaiian Electric also proposes to use as much of the existing infrastructure, including an existing substation, for the Waiau Repowering project. The site is located within the State Urban Land Use District and designated as an intensive industrial zone. Thus, no new zoning changes will be required.

The project also supports the Primary Urban Center Development Plan (2004), which specifies policies related to electrical power in the Primary Urban Center. In Section 4.3.2 of the PUCDP, it’s the position of the City & County of Honolulu, to:

  • “Support retention and upgrade of the Waiau and Honolulu Power Plants as part of a strategic plan to improve the reliability of the Primary Urban Center’s electrical power system.”

The Waiau Repowering project, which consists of retaining and upgrading the existing generation capacity with modern units, is consistent with and supportive of the PUCDP.

The Waiau Power Plant is also the nearest power generation facility to Oahu’s business district, tourist center in Waikiki, and National Defense infrastructure facilities. Maintaining electrical support to critical infrastructure is a high priority for Hawaiian Electric.

The project will not add to existing development around the Waiau Power Plant footprint, ensuring that community group projects such as community gardens and harbor shoreline restoration efforts can continue uninterrupted in the area.

Hawaiian Electric intends to hire local labor to the extent that the skills and expertise needed for the project can be obtained in Hawaii; and pay wages and benefits appropriate to the skilled trade needed to construct and install the project.

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