Waena Battery Project: First Tesla Megapacks arrive, bringing Maui closer to a more renewable grid

Construction of Hawaiian Electric’s Waena Battery Energy Storage System (BESS) reached a major milestone with the arrival of the first six Tesla Megapacks at the project site along Pulehu Road in Central Maui.

Delivered by semi-truck and carefully lifted into place by crane, the Megapacks, each roughly the size of a 40-foot shipping container, are the first of 54 battery units. These will make up Maui’s first standalone load-shifting battery energy storage system.

“This project has been years in the making, and seeing the batteries arrive on site brings us one step closer to providing Maui with a more renewable electric grid,” said Shelley Takasato, manager of Generation Project Development for Hawaiian Electric.

Located on Hawaiian Electric-owned property, the project will be a 40-megawatt (MW), 160-megawatt-hour (MWh) battery energy storage system. Rather than generating electricity, the battery system will capture and shift energy from resources such as solar and wind to better match customer demand.

Supporting a more renewable grid

Maui’s transition to clean energy is well underway. In 2025, more than 41% of the electricity generated for Maui County came from renewable resources, reflecting progress toward Hawaii’s goal of generating 100% of its electricity from renewable resources by 2045.

As more renewable energy comes online, battery storage is increasingly important to ensure that energy is available when customers need it most. For example, solar energy generated on a sunny afternoon can be stored and used later in the evening, when customers are returning home, cooking dinner and using more electricity. By storing energy for later use, the project will help maximize Maui’s renewable energy resources.

What is grid-forming technology?

Beyond storing energy, the project will utilize grid-forming technology.

Historically, conventional synchronous machine-based power plants have helped maintain an electric grid’s frequency and voltage during system disturbances. While many renewable energy resources can generate electricity, they have traditionally relied on those synchronous machine-based power plants to keep the grid stable.

As the share of renewable energy resources increases, new technologies are needed to provide stability. Grid-forming batteries can fill that role by emulating synchronous machines and responding almost instantaneously to changes on the system.

“As Maui continues adding renewable energy to the grid, projects like Waena help ensure we can maintain the reliability our customers depend on,” Takasato said.

Simply put, the Waena BESS will both store energy and support the grid itself.

Proven technology, now coming to Maui

Maui is not the first island to benefit from this kind of battery technology.

On Oahu, the Kapolei Energy Storage facility also utilizes Tesla Megapacks with grid-forming technology and has demonstrated how battery storage can support grid reliability and integrate more renewables. Kapolei’s success provides confidence that similar benefits can be realized on Maui.

While the Kapolei project was developed by an independent power producer, the Waena BESS is a significant step for Hawaiian Electric as its first utility-developed battery energy storage project. Approved by the Public Utilities Commission in 2023, the project reflects Hawaiian Electric’s growing role in developing and operating modern grid resources that support Hawaii’s clean energy goals.

What’s next?

The installation of the remaining units is expected to be completed by the end of October.

Following battery installation, crews will install transformers, control systems and other equipment before the system undergoes extensive testing and is placed into service.

Expected to come online in 2027, the Waena BESS will help modernize Maui’s electric grid, support greater use of renewable energy and reduce reliance on fossil fuels while maintaining reliable service for customers.