Improvement Valuation of Commercial Solar Energy Systems
Administered by: Illinois Department of Revenue
Quick Summary
If you own a commercial solar energy system that generates electricity for wholesale or retail sale in Illinois (in counties under 3 million people), your property taxes will be calculated using a standardized formula rather than standard property assessment. The formula bases the system's value on $218,000 per megawatt of nameplate capacity (adjusted annually for inflation), then subtracts depreciation allowances. Contact your county assessor or the Illinois Department of Revenue for details on how this affects your specific property tax bill.
AI-generated summary • Updated 7/12/2026
Program Details
- Program ID
- 22439
- Effective Date
- 8/10/2018
- Expiration Date
- 12/31/2033
- Last Updated
- 3/17/2025
Eligibility
Program Summary
Illinois uses a specific formula to value commercial solar energy systems for property tax purposes in counties with fewer than 3 million inhabitants. "Commercial" in this sense means that the system is used primarily to generate electricity for wholesale or retail sale, rather than referring to the customer class. The valuation formula is calculated by substracting allowance for physical depreciation from the trended real property cost basis (set at $218,000 per MW of nameplate capacity in 2018, with adjustments for CPI inflation). More information is available here.
Contact & Resources
Please verify current program details with the administering agency before making any financial decisions.