See how much you can save by switching to solar hot water — personalized for your zip code and household
Your zip code maps to Hawaii's GIS Solar Radiation database, which measures actual sunlight intensity (cal/cm²/day) at your location. Leeward areas get up to 525 cal while windward valleys get 325 cal — a 60% difference that dramatically affects SWH performance.
Hot water usage scales with household size — roughly 4.5 kWh per person per day. We size the system and estimate savings based on your actual household, not generic averages.
Calculations include the Hawaii 35% state tax credit (up to $2,250) and the Hawaii Energy rebate (increased through June 2026). These can cut your net cost by 40-60%.
25-year savings account for 3% annual electricity rate increases. With HECO rates already at $0.41/kWh and rising, solar hot water savings compound significantly over time.
Solar hot water performance varies dramatically across Oahu. Leeward and south shore locations receive up to 60% more solar energy than windward valleys.
| Zone | Solar Radiation | Rating | Areas | SWH Solar Fraction |
|---|---|---|---|---|
| 10 | 500+ cal/cm²/day | Excellent | Ewa Beach, Kapolei, Pearl City, Kaimuki, Waikiki, Aiea | 85% |
| 8-9 | 450-500 | Very Good | Waipahu, Mililani, Haleiwa, Hawaii Kai, Kahala | 78-82% |
| 6-7 | 400-450 | Good | Kailua, Wahiawa, Manoa, Salt Lake | 72-75% |
| 4-5 | 350-400 | Moderate | Waimanalo, Laie, Kalihi Valley | 65-68% |
| 1-3 | 300-350 | Below Average | Kaneohe, Kaaawa, upper valleys | 55-62% |
Source: Hawaii State GIS Program Oahu Solar Radiation Map. Solar fraction = percentage of hot water demand met by solar.
Hawaii Energy rebates are increased through June 2026. Get a free estimate now.
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