Illinois is one of the most active SREC markets in the country, driven by the Illinois Shines Adjustable Block Program. The combination of 15-year SREC contracts, retail-rate net metering, and the federal ITC creates compelling economics for both residential and commercial solar across the state.
Illinois Solar Snapshot
NEC Edition: 2020 | Primary Utilities: ComEd (Chicago/northern IL), Ameren Illinois (central/southern IL) | Net Metering: Mandatory (retail rate; annual excess at wholesale) | SREC Program: Illinois Shines (15-year contracts) | Federal ITC: 30% residential / up to 50% commercial
Illinois Shines — SREC Adjustable Block Program
Illinois Shines is the cornerstone financial incentive for Illinois solar:
How Illinois Shines Works
- Solar system generates electricity → one SREC is issued per 1,000 kWh (1 MWh) of production
- SRECs are sold to Illinois utilities that need them to meet the Renewable Portfolio Standard (RPS)
- Illinois Shines provides 15-year contracts at a fixed SREC price
- Systems under 10 kW apply through Approved Vendors (solar companies certified by the IPA)
- Systems over 10 kW apply directly through the IPA portal
Current SREC Pricing
SREC prices in the Illinois Shines program are set by the Adjustable Block Program based on project type and system size. Prices are updated periodically:
| System Type | Pricing Structure |
|---|---|
| Residential (under 10 kW) | Fixed price, 15-year contract |
| Small commercial (10–2,000 kW) | Block pricing, 15-year contract |
| Large commercial (over 2 MW) | Competitive bid process |
Contact the Illinois Power Agency (IPA) or an Illinois Shines Approved Vendor for current SREC prices — they change as blocks fill.
Illinois Shines Approved Vendor Requirement
For residential and small commercial systems, you cannot enroll directly in Illinois Shines. You must work with an IPA-certified Approved Vendor (AV). The AV handles enrollment, SREC contract execution, and ongoing SREC registration. Many solar installers in Illinois are certified AVs — confirm before signing a contract that your installer is an IPA Approved Vendor.
ComEd Interconnection
ComEd (Commonwealth Edison) serves Chicago and northern Illinois (~70% of the state’s population):
| System Size | Process | Timeline |
|---|---|---|
| Under 10 kW residential | Small Generator | 10–20 business days |
| 10 kW–2 MW | Level 1 study | 45–90 days |
| Over 2 MW | Level 2 study | 6–18 months |
ComEd required documents:
- Completed interconnection application
- One-line electrical diagram
- Equipment specifications (inverter, modules, disconnects)
- Illinois Commerce Commission interconnection standard compliance
Ameren Illinois Interconnection
Ameren Illinois serves central and southern Illinois (Springfield, Peoria, Champaign, metro-east St. Louis area):
- Application process mirrors ComEd’s structure
- Ameren portal: amerenil.com/solar
- Same size tiers and timelines as ComEd
Illinois Net Metering
Illinois mandates net metering under the Public Utilities Act:
| Parameter | Details |
|---|---|
| Eligible size | Up to 2 MW |
| Credit rate | Full retail rate |
| Monthly carryover | Yes |
| Annual true-up | October 31 — excess paid at wholesale market price |
October 31 true-up: unused credits are paid at the wholesale market price (typically $0.03–0.06/kWh) — not forfeited, but well below retail. Right-sizing to avoid large annual excess is advisable.
Chicago Permitting
Chicago has its own electrical code with Chicago-specific amendments to the NEC. Key points for Chicago solar:
Chicago Solar Permit Program
Chicago’s streamlined solar permit process for residential systems:
- Applies to systems under 25 kW on single-family and 2-flat residential structures
- Reduced documentation requirements vs. commercial permit
- Plan review: 5–10 business days
- Chicago SolarAPP+ participation: confirm current status with DOB
Commercial Solar in Chicago
- Full plan review required
- Chicago Department of Buildings — Commercial Plan Examination
- Chicago historic district review if applicable (many Chicago neighborhoods have historic designations)
- Timeline: 15–45 business days for plan approval
Chicago Historic Districts
Chicago has numerous historic districts and landmark buildings where visible solar installations require Chicago Landmarks review in addition to standard permitting. If the project is in a potential historic district, identify this early — historic review can add 4–8 weeks and may restrict panel placement to rear roof surfaces only.
Illinois Climate — Conductor Derating
Chicago’s climate requires consideration for both summer heat and cold winter temperatures:
| Parameter | Chicago Value |
|---|---|
| ASHRAE max air temp | 34°C |
| + 22°C rooftop adder | +22°C |
| Effective conductor temp | 56°C |
| THWN-2 (90°C) correction factor | 0.76 |
| ASHRAE min air temp (for Voc) | -22°C |
Chicago’s cold minimum temperature (-22°C) requires NEC 690.7 string voltage calculation:
For Voc = 45.0V, β_Voc = -0.30%/°C:
Factor = 1 + (-22 - 25) × (-0.003) = 1 + 0.141 = 1.141
Corrected Voc per module = 45.0 × 1.141 = 51.3V
Max modules (600V) = 600 ÷ 51.3 = 11.7 → 11 modulesFederal ITC in Illinois
| System Type | Credit | With Bonuses |
|---|---|---|
| Residential (Section 25D) | 30% | N/A |
| Commercial (Section 48E) | 30% base | Up to 50% |
Former Illinois coal plant communities (Waukegan, Joliet, Springfield area) may qualify for the IRA energy community bonus (+10%).
Illinois Shines + NEC 2020 Compliance in One Package
SurgePV generates Illinois Shines-compatible production estimates and NEC 2020-compliant permit packages — formatted for ComEd and Ameren interconnection and Chicago Department of Buildings review.
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Frequently Asked Questions
What is Illinois Shines?
Illinois Shines is the state’s Adjustable Block Program for solar SRECs. Residential and commercial systems earn SRECs (one per MWh of production) and sell them through 15-year contracts to Illinois utilities. Residential systems work through IPA-certified Approved Vendors. It is one of the most valuable state SREC programs in the US.
How does ComEd net metering work?
ComEd credits excess solar at the full retail rate monthly. Annual true-up occurs October 31 — unused credits are paid at the wholesale market price (typically well below retail). Systems up to 2 MW are eligible.
What permits are required for Chicago solar?
Chicago Department of Buildings permits are required — both building and electrical. Chicago’s Solar Permit program expedites residential systems under 25 kW. Chicago has additional local requirements beyond state NEC adoption, including Chicago Electrical Code amendments.
