Scope
Public Act 104-0458 (Senate Bill 25, the Clean and Reliable Grid Affordability Act) amends section 39 of the Illinois Environmental Protection Act (415 ILCS 5/39). Air pollution construction permits for diesel backup generators at a data center, as defined in 20 ILCS 605/605-1025, that are applied for 6 months after the act takes effect and that need a FESOP or Title V permit must meet standards at least as protective as EPA Tier 4 non-road diesel standards; natural-gas backup generators must meet standards at least as protective as Tier 2. The generators may operate only as emergency or standby units, with the outage allowance the act states.
- Geographic scope
- Illinois
- Jurisdiction
- State
- Authority type
- Legislature
- Issuing authority
- Illinois General Assembly
Dates
- Adopted
- 8 January 2026
- Effective
- 1 June 2026
- Scheduled expiration
- See completion condition
- Ended
- Not recorded as ended
- Completion condition
- The act states no expiration. Its generator standards apply to permit applications made 6 months after the effective date; that applicability date is not stored as a separate day.
- Source document
- The source page states no document date
- Last checked
- 23 September 2026 (earlier than tracker date 5 October 2026; not an automatic status change)
Summary
Illinois Public Act 104-0458 sets emission standards for backup generators at data centers that seek air construction permits. Diesel backup generators must meet standards at least as protective as Tier 4, and natural-gas units standards at least as protective as Tier 2, for covered permit applications made 6 months after the act's effective date, and they may operate only as emergency or standby units. The Governor approved the act on 8 January 2026 and it took effect on 1 June 2026. This record covers only the data center generator provisions, not the act's other grid provisions.
What this does not establish
- The approval and effective dates come from the official bill-status page for SB 25, a supporting source.
- The act's other large-load and grid provisions are not data-center-specific and are not part of this record.
- No Illinois EPA or Pollution Control Board rule or guidance implementing the generator standards was found on the agencies' rulemaking pages opened on 23 September 2026.
- The exact start of the 6-month applicability window was not computed.
- The compiled 415 ILCS 5/39 on ilga.gov shows a later amendment by Public Act 104-747, effective 1 January 2027, that adds PFAS sampling provisions for NPDES permits; the data center backup generator paragraphs read the same in the versions before and after that amendment.
Unresolved questions
- How the Illinois EPA will apply the standards to pending applications was not established.
Relationships
Supersession means a later instrument replaces the earlier legal effect. Repeal links identify the repeal instrument and the measure it ends. A later implementation or related letter is not treated as a replacement unless the record says so.
- Related, not a replacement Data Center Investment program tax exemptions and credits (In effect)
Sources
https://www.ilga.gov/Documents/Legislation/PublicActs/104/PDF/104-0458.pdf
- SB 25 bill status (104th General Assembly) official bill status showing Governor approval on 8 January 2026 and effective date 1 June 2026
- 415 ILCS 5/39 as compiled on ilga.gov compiled section showing the generator standards and the later P.A. 104-747 amendment effective 1 January 2027