Illinois Solar Calculator

Your home

Average monthly electric bill

Use a typical month — or average a few. We convert it to yearly usage using your utility's real rates.

Your utility Your roof's sun

Adjust the assumptions

Installed cost per watt: $3.00

Illinois quotes we've seen run $2.60–$3.40/W. The results always show that full range too.

Share of solar power you use at home: 70%

Power used at home saves the full retail rate. Power exported earns only the supply rate under Illinois net billing — that split is the number installers don't show you.

Your estimate

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Recommended system

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Payback period

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Saved per year

Your estimated yearly usage	–
System production per year	–
Installation cost	–
Utility DG rebate	–
Illinois Shines SRECs (15-yr total)	–
Estimated net cost	–
Your bill after solar	–
25-year gross savings	–

Get exact quotes for my numbers →

Estimates only — your real quotes will vary with your roof, equipment, and current incentive blocks. No email needed to see your numbers; we only ask for details if you request quotes.

Your 10-year cash picture

The line starts below zero — that's your real out-of-pocket after rebates and solar credits. Every year of savings climbs it back; where it crosses zero is your breakeven.

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Installation cost (midpoint)

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Rebates + SRECs

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Your net outlay, day one

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Savings over 10 years

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Your position at year 10

How we calculate (nothing hidden)

Usage: (your monthly bill − the utility's fixed monthly charge) ÷ the per-kWh variable rate × 12. ComEd's rates come from a real August 2026 bill we took apart — supply 10.4¢/kWh, about 17.6¢/kWh avoidable all-in, $19.37/month fixed.
Size: we target ~95% of your usage, not 100%+ — under net billing, overproducing earns the low export rate. Chicago-area yield: ~1,200 kWh per kW per year, adjusted for your shade.
Incentives: utility Distributed Generation rebate ($300/kW where offered) and Illinois Shines SRECs at $70–$85 per credit over a 15-year contract. The federal tax credit is $0 for homeowner-owned systems in 2026 — it ended, and any quote still showing it is a red flag.
Savings: self-used solar saves the full variable rate; exported solar earns the supply rate only. Fixed monthly charges stay on your bill either way.
See the whole method worked end-to-end on a real bill: our Homer Glen case study.