Hawaii’s energy transition is defined by its extreme geographic isolation in the Pacific Ocean. The state operates as a collection of independent energy systems, separated from the mainland United States and from one another. This isolation has historically created unique economic and technical challenges for power generation. Faced with the highest electricity costs in the nation, Hawaii has aggressively pursued a rapid, government-mandated shift away from imported fuels toward local, sustainable power sources.
The Historical Reliance on Imported Fossil Fuels
For decades, Hawaii’s electricity generation relied overwhelmingly on imported petroleum (oil). Because the islands have virtually no indigenous fossil fuel reserves, nearly all the fuel had to be shipped across vast ocean distances. This reliance on a volatile global commodity meant that consumers consistently paid electricity prices often triple the national average.
The state’s dependence on imported oil made the local economy vulnerable to international market fluctuations and supply chain disruptions. The state took a significant step toward decarbonization with the closure of the AES Hawaii coal plant on Oʻahu in September 2022. This phase-out of the island’s largest single generator marked a pivot in the state’s energy strategy. The transition increased pressure on renewable resources and remaining oil-fired generators to maintain grid stability.
Hawaii’s Diverse Renewable Energy Sources
The transition has spurred the development of a broad portfolio of local renewable resources, led by solar power. Hawaii has achieved one of the highest penetrations of residential rooftop solar photovoltaic (PV) systems in the country, with approximately one in three homes using it. This distributed generation has historically produced more clean energy than all utility-scale solar farms combined.
Utility-scale solar farms are also being constructed across the islands to meet bulk energy needs. Wind power plays a significant role, with utility-scale wind farms operating on Oʻahu, Maui, and the Island of Hawaiʻi. These intermittent sources introduce complexity into managing the isolated island grids.
To provide a stable, non-intermittent power supply, the state leverages its unique geology for geothermal energy. The Puna Geothermal Venture (PGV) on the Island of Hawaiʻi is the state’s only commercial geothermal plant, providing a source of firm, or baseload, power. The plant uses heat from the Kīlauea volcano’s East Rift Zone to generate up to 38 megawatts of continuous electricity. Limited hydroelectric capacity, primarily on Kauaʻi and the Island of Hawaiʻi, and bioenergy from burning biomass and municipal waste, round out the diverse portfolio.
Managing the Isolated Island Grids and Energy Storage
Hawaii’s geography dictates that its electricity system consists of six separate, self-contained grids, one for each major populated island. The immense depth of the ocean channels makes inter-island transmission cables technically challenging and economically prohibitive. Consequently, each island grid must operate in complete electrical isolation, requiring it to match its generation to its own demand in real-time.
This isolation is a technical hurdle when integrating variable renewable sources like solar and wind, as there is no continental grid to import backup power during lulls. To overcome the intermittency challenge, utility-scale Battery Energy Storage Systems (BESS) are being deployed. These battery systems act as an electrical “shock absorber,” absorbing surplus solar energy during the day and discharging it to meet peak demand in the evening.
The Kapolei Energy Storage (KES) facility on Oʻahu is a prime example, providing 185 megawatts of instantaneous discharge capacity, comparable to the output of the retired coal plant it replaced. The system uses advanced features like synthetic inertia and fast frequency response to stabilize the grid. It can even provide “black start” capability to help restore power in the event of a total blackout. This large-scale storage is essential for maintaining reliability while increasing the share of variable renewable power.
The 100% Renewable Energy Mandate
The state’s energy transition is driven by the legislative directive, Act 97, signed into law in 2015. This law mandates that 100% of the electricity sold in Hawaii must come from renewable energy resources by 2045. The mandate includes interim targets, such as achieving 30% renewable electricity by 2020 and 70% by 2040, providing a clear roadmap for utilities.
This goal makes Hawaii the first state in the nation to commit to a 100% renewable portfolio standard for electricity. The policy is intended to replace the economic drain of imported fossil fuels with local energy generation, bolstering energy security and creating a more resilient system. Progress toward the mandate continues, with the state actively working to integrate new renewable generation and grid modernization technologies to meet the 2045 deadline.