Same size system, same math, two different states — here's what actually changes between Illinois and Indiana, and which one gets you to break-even faster.
Same size system, same math, two different states — here's what actually changes between Illinois and Indiana, and which one gets you to break-even faster.
| Metric | Illinois | Indiana |
|---|---|---|
| Average residential rate | $0.16/kWh | $0.15/kWh |
| Peak sun hours/day | 4.2 hrs | 4.1 hrs |
| Typical 6kW system cost | $16,800 | $16,200 |
| Estimated annual production | 7,358 kWh | 7,183 kWh |
| Estimated payback | 14 years | 15 years |
| Net metering | Net metering plus separate SREC-style incentive (Illinois Shines) | Net metering being phased down to a lower excess-credit rate by utility |
Illinois comes out ahead on estimated payback — roughly 14 years for a standard 6kW system, against 15 years in Indiana, a gap of about 0.8 years. That difference comes from the combination of electricity rate and net metering terms, not system cost alone: a cheaper system in a state with a low electricity rate to offset can still pay back slower than a pricier system in a state where every kWh saved is worth more.
Illinois: Illinois Shines pays an upfront, capped incentive per system on top of standard net metering — a genuinely strong state program. Indiana: Indiana's net metering excess-credit rate has been declining for newer systems — check your specific utility's current rate. Neither state's homeowners get the federal residential tax credit for systems installed in 2026 — it expired December 31, 2025 — so these numbers already reflect that reality rather than the older 30%-off assumption still floating around in outdated articles. See our full 2026 tax credit guide for the details.
Payback speed isn't the only thing that matters. If you're comparing these two states because you're deciding where to buy a home or how to plan a move, also weigh how long you expect to stay — a slower-payback state can still make sense if you'll own the home long enough to get well past break-even, since every year after that is pure savings either way. And if either state has a meaningful gap between peak and off-peak electricity rates, a battery can improve the economics further than the panel-only comparison above shows — check that separately with the Battery ROI / Time-of-Use Calculator.
Illinois has the faster estimated payback of the two, at roughly 14 years for a 6kW system versus 15 years in Indiana — a gap of about 0.8 years, driven mainly by the difference in electricity rates and net metering terms between the two states.
Illinois's average residential rate is $0.16/kWh, compared to $0.15/kWh in Indiana — a difference of $0.01/kWh.