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Hanalei Valley. Photo: Gh5046, public domain

Think B.I.G. Hawaiʻi · Energy Self-Reliance map · Kauaʻi

How energy self-reliant is Kauaʻi?

Kauaʻi’s member-owned co-op runs one of the greenest grids in the state, with about half its power from the sun, rivers and biomass. Count the gasoline, diesel and jet fuel too, and only about one unit of energy in seven used on the island is made here. See how we got here, where today’s plans lead, and what 95% would take.

53%of the grid’s power is renewable2025, share of generation
14%of all energy used comes from island sources2025, every fuel counted
86%renewable grid by 2035 on current plansmodel projection
24%all-energy self-reliance by 2035 on current plansmodel projection
▶ Play the map Try the 95% simulator Plans vs. reality
Where we are

A co-op grid, second in the state

Kauaʻi’s grid is run by KIUC, a member-owned cooperative, not Hawaiian Electric. It pairs large solar farms with batteries, small hydro plants on the island’s streams, and the Mahipapa biomass plant, which returned to service in 2025. Renewables made 52.8% of the island’s power that year, by the state’s official measure, second only to the Big Island.

But the grid is only one slice. Cars and trucks, boats, flights and industry run almost entirely on imported fuel. Count every fuel, and only about 14% of the energy used on Kauaʻi comes from island sources.

Renewable share of the grid53%
Island-made share of all energy14%
The Wailua River winding through green hills on Kauaʻi
The Wailua River, east Kauaʻi. Hydro on the island’s streams dates back to the sugar plantations. Photo: Bret Robertson, CC BY 2.0
How the model works

Every fuel, in the same units

The model starts from 2025 data, including utility renewable-energy reports and state fuel-tax records for gasoline, diesel and aviation fuel. It converts every fuel to the same energy units, so electricity, transport, shipping, flights and industry can be added together.

A simple year-by-year model then adds the projects KIUC has under contract: Kaʻawanui and Mānā lift the grid to the high 80s by 2030. Without more projects it stays in the mid-80s, and KIUC’s goal of 100% renewable power by 2033 is missed. All-energy self-reliance stays near a quarter through 2035.

GeothermalWindHydroSolar + batteriesBiomassImported oil
A small shopping center with solar panels on the roof, under palm trees
Rooftop solar at the ʻEleʻele Shopping Center, west Kauaʻi. Photo: ECTran71, CC BY-SA 4.0
Where it could go

What 95% would take

The 95% pathway goes further: faster solar and storage, firm renewable power, electrified industry, island-made fuels for boats and planes, and EV sales climbing along an S-curve, from today’s 14% of new cars to about 63% in 2035 and 91% in 2040.

Because cars stay on the road about 22 years, that last step sets the pace: on this path Kauaʻi doesn’t reach 95% of all its energy until after 2060. Add trade-ins of old cars and more island-made fuel, and the simulator gets there by 2039. Every grid is capped at 99% renewable, so some fuel-fired backup always stays on for caution. These are planning sketches, not utility forecasts; the assumptions and sources are listed below the simulator.

Try the simulator →
solarbatteryhomes
Illustration: solar fills the batteries by day, and the batteries carry homes through the night.
2025

Share of electricity sales by source

KIUC filings, 2005–2025.

2025

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Renewable share of grid
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All-energy self-reliance
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Battery storage
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Icons show the technology; the colored halo’s area = nameplate MW. Dashed halos: planned but never built, not yet built, or offline. Contours are schematic (a simple cone model of Kauaʻi’s central shield volcano), not survey data. Green dots: rooftop solar, one dot ≈ 1 GWh a year; grey dots: off-grid homes (estimate). Moving cars, planes and boats are colored by what powers them: green = electric, light green = island-made fuel, terracotta = imported fuel; their share of each color follows the model, not counts of real vehicles. EV shares before 2025 are approximate. Plant locations are approximate.

What KIUC planned, and what happened

Renewable share of Kauaʻi’s electricity: plans vs. actual

As KIUC reported it: share of sales through 2021, share of generation from 2022 (Act 240). Hollow points are interpolated years.

Each plan for Kauaʻi, in brief

  • 2008 board goal: 50% renewable by 2023. Reached in 2019, four years early.
  • 2017–2021, dispatchable solar: Tesla’s Kapaia plant (13 MW + 52 MWh, 2017), AES Lāwaʻi (20 MW + 100 MWh, 2019) and AES PMRF (14 MW + 70 MWh, 2021) carry renewables to a 69.5% peak in 2021.
  • West Kauaʻi Energy Project (PPA 2021): 35 MW of solar with 240 MWh of pumped hydro, meant to take Kauaʻi past 80% “by 2024.” Delayed by water-rights litigation; KIUC dropped the flow-through hydro part on Dec 13, 2023, and the rest is uncertain.
  • 2023–2033 Strategic Plan (adopted Jan 17, 2023): 100% renewable by 2033, 12 years ahead of the state mandate.
  • Kaʻawanui and Mānā (PUC-approved Mar and Apr 2026): 43 MW + 172 MWh and 35 MW + 140 MWh of solar + storage. KIUC says Kauaʻi could approach 90% by 2030 if both are built.
  • KIUC is not part of Hawaiian Electric’s PSIP or IGP process; it plans through its own strategic plans and PUC-approved contracts.

2035 on current plans

Kaʻawanui and Mānā lift the grid to the high 80s by 2030. Without more projects it stays in the mid-80s, and KIUC’s 100%-by-2033 goal is missed. Cars, trucks, boats, planes and industry still run on imported fuel, so all-energy self-reliance stays near a quarter.

Simulator: what gets Kauaʻi to 95% self-reliance?

Choose what to build and when. Results update as you move the controls. Start from a preset, then adjust.

Goal
Firm renewable power and long storage
Million gallons a year, reached by the year set under boats and flights. KIUC began buying biodiesel in 2023; amounts aren’t public.
Solar, wind and storage
KIUC notes Kauaʻi lacks strong wind and geothermal resources.
Cars and trucks

EV share of new-vehicle sales over time: pick a curve, or shape your own.

The year sales are halfway from today’s 14% to the long-run share. Sales follow an S-curve: slow, then fast, then leveling off.

Not part of the Hawaii EV Association calculator, and off in every preset except “All levers”. It would take a trade-in (cash-for-clunkers) program: 1% of all cars a year is about 11,000 extra cars statewide.
Buildings and industry
Boats and interisland flights
Million gallons a year made on-island.
All-energy self-reliance in goal year
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Self-reliance over time

All energy used on the island, by where it comes from (GWh-equivalent)

What this scenario asks the island to build

ItemThis scenarioReality check
How this works, assumptions, and sources

Method

All-energy self-reliance = island renewable electricity actually used, plus off-grid solar and fuels made on-island, divided by all energy used on the island: grid electricity, road gasoline and diesel, marine fuel, interisland jet fuel, propane and off-road diesel. Energy-content basis, as in the ESR framework. Transpacific flights and shipping are out of scope.

Grid dispatch is annual, with a simple day/night split: biomass, hydro and wind serve load around the clock; solar serves the daytime half of what’s left; batteries and pumped hydro (one cycle a day, 88% round trip) move surplus solar into the night; biofuel and then oil plants fill the rest. Surplus solar is curtailed unless e-fuels are switched on (50% conversion). This is a planning sketch, not a reliability study. Backup floor: each grid tops out at 99% renewable. We assume fuel-fired backup plants still supply at least 1% of each year’s electricity (storms, outages, maintenance, long windless or cloudy spells), and that every island keeps some backup for caution and diversity.

2025 starting point matches KIUC’s 2025 filing: 52.8% renewable (24.5% utility solar, 14.3% rooftop, 9% hydro, 5% biomass), on an estimated 566 GWh of generation.

Key assumptions (low confidence flagged)

  • Total 2025 generation ≈ 566 GWh: EIA-923 utility-scale generation (485.5 GWh) divided by the non-rooftop share (low).
  • Base demand +0.5%/yr before electrification.
  • Road fuel: 29.4M gal gasoline + 2.2M gal highway diesel (DoTax 2024, Kauaʻi County). EVs use 7.3 kWh per gallon of gasoline replaced and 12 kWh per gallon of diesel; 3.6% of cars electric at the end of 2025 (DBEDT: 42,919 of 1,082,932 passenger vehicles by Sept 2026). Fleet turnover, using the same method as the Hawaii EV Association site calculator: about 50,000 new vehicles join each year and stay ~22 years; today’s EVs leave the road at ~6% a year; the EV share of new sales (13.8% in 2025, HADA) drives the fleet. Even 100% EV sales from 2027 leaves 10% of cars on gas until about 2046. Trucks and buses are assumed to lag cars by five years. “Current plans” holds EV sales at today’s ~14%; the ESR pathway’s EV sales follow the “Steady” S-curve (about 26% of new cars in 2030, 63% in 2035, 91% in 2040), with no early retirement. Island-made fuels go to boats and planes; a switch extends them to the remaining gas and diesel vehicles.
  • Interisland jet fuel 349 GWh-eq (Kauaʻi’s 7.4% share of state aviation fuel applied to the ESR workbook’s interisland total) and marine 86 GWh-eq (low).
  • Propane ~2.8M gal (7% of ~40M gal statewide) and ~2M gal of off-road diesel outside power plants; most of Kauaʻi’s 18M gal of off-road diesel feeds KIUC’s engines (low).
  • Mahipapa biomass returns to ~50 GWh a year from 2026 (about 9–10% of generation, as in 2022). Hydro held at its 2025 level (9%); it was 12% in 2023.
  • Kaʻawanui adds 100 GWh/yr and 172 MWh from 2029; Mānā 86 GWh/yr and 140 MWh from 2030 (KIUC/AES figures).
  • 2025 batteries: 222 MWh (Kapaia 52, Lāwaʻi 100, PMRF 70). New rooftop solar adds ~1 MWh of usable home battery per MW (low).
  • Electrifying industry and boats uses 0.4 units of electricity per unit of fuel replaced; electric aircraft the same.
  • Plant capacities for hydro are approximate; Kauaʻi has a little over 16 MW of hydro in total.

Sources

  1. KIUC 2025 RPS filing, reported in The Garden Island (May 2026) and Kauaʻi Now (2025 mix).
  2. KIUC, 2015 RPS Status Report (PUC Docket 2007-0008): 2005–2015 renewable energy, efficiency savings and sales.
  3. KIUC annual results: 2017 (Star-Advertiser); 2019, 56.6%; 2021, 69.5%; 2022, 60.2%; 2023, 57.9%; 2024, 50.6% and the 2023–2033 Strategic Plan.
  4. Canary Media: the 2008 board goal of 50% by 2023.
  5. AES Hawaiʻi project list (Lāwaʻi, PMRF, Kaʻawanui, Mānā); Utility Dive (Tesla Kapaia 13 MW + 52 MWh); The Garden Island (Kaʻawanui and Mānā output and prices).
  6. HSEO CREDIT Task Force master schedule, May 2026: Kaʻawanui and Mānā approvals and dates.
  7. West Kauaʻi Energy Project: “Plan for largest Hawaii hydroelectric plant is downsized” (Star-Advertiser); PUC Report to the 2024 Legislature on RPS (Dec 13, 2023 discontinuation; ~40.6 MW of rooftop solar).
  8. EIA-860/923 plant data via GridInfo and interconnection.fyi (Port Allen, Kapaia, Wainiha).
  9. Hawaiʻi Department of Taxation, Liquid Fuel Tax Base, CY2024; LP Gas, Propane Fuels America: Hawaii.
  10. Think B.I.G. Hawaiʻi, ESR Framework workbook (draft, May 2026): sector scope and interisland aviation and marine totals.

Export your results

Save the year-by-year numbers for current plans and the scenario now set in the simulator, as a spreadsheet or a short PDF report. The map picture shows the year currently selected on the map’s slider.