Solar panel ROI varies wildly across the United States — but not for the reasons most people think. I built a free calculator using data from the NREL PVWatts API and EIA electricity rates to compare every state. Here's what the data shows.
The Surprising Finding: Electricity Rates Matter More Than Sunshine
Most people assume the sunniest states have the best solar ROI. The data tells a different story.
Arizona gets the most sunshine (6.54 kWh/m²/day) but only ranks mid-pack for ROI at 2.5x with about a 10-year payback. Why? Because electricity is cheap there — so each kWh your panels generate saves you less money.
Hawaii has the highest ROI at 5.9x with a 4.2-year payback — not because of more sun (5.82 kWh/m²/day, less than Arizona), but because electricity costs are extremely high. Every kWh produced saves significantly more.
Massachusetts beats Arizona on ROI (3.7x vs 2.5x) despite getting way less sun (4.7 vs 6.54 kWh/m²/day). Again — higher electricity rates drive better financial returns.
The Top 5 States for Solar ROI
| State | ROI | Payback | Solar Irradiance | Why |
|---|---|---|---|---|
| Hawaii | 5.9x | 4.2 years | 5.82 kWh/m²/day | Extremely high electricity costs |
| California | 4.5x | 5.6 years | 5.87 kWh/m²/day | High rates + strong sun |
| Massachusetts | 3.7x | 6.8 years | 4.70 kWh/m²/day | High electricity rates |
| New York | 2.5x | 10 years | 4.48 kWh/m²/day | Above-average rates |
| Arizona | 2.5x | 10 years | 6.54 kWh/m²/day | Best sun, but cheap power |
The Worst State
Alaska comes in last at 1.4x ROI with a 17+ year payback. Only 2.4 kWh/m²/day of solar irradiance makes it almost impossible for panels to generate enough energy to justify the cost.
How I Built This
I pulled data from two free government APIs:
- NREL PVWatts API — models solar energy production based on location-specific irradiance, weather, and panel angles. Assumes a standard 6kW residential system.
- EIA — provides state-level residential electricity rates.
The ROI formula: (annual production × electricity rate × 25 years) / system cost.
I built the calculator with Astro (zero JavaScript, static HTML) and deployed on Cloudflare Pages for free. Each state page lets you adjust system size, cost, and electricity rate to see personalized estimates.
Try It Yourself
The full calculator is free at solar-roi-13a.pages.dev — no signup, no ads. Pick your state, adjust the inputs, see your ROI.
All the data comes from official government sources. I'd love to hear if the estimates match what you've seen from real-world solar installations.
What I Learned
- Location economics > weather for solar ROI
- Government APIs are underused — NREL, BLS, USDA, FCC all have free, high-quality data
- Static sites are powerful — 500+ pages, zero hosting cost, instant page loads
- This is part of a larger project where I'm building free data tools from government APIs covering solar, nutrition, salaries, and more.
Data sourced from NREL PVWatts API and EIA. Estimates don't include the federal 30% ITC tax credit, state incentives, or utility rebates, which would improve ROI further.
