IL SB2727

Defines "battery storage resource" and "total State-installed generation capacity" in the Environmental Protection Act's greenhouse gas provisions

Prohibits variances or regulatory relief from emissions reduction obligations only when battery storage resources constitute at least 10% of total State-installed generation capacity

Requires the Illinois EPA to delay enforcement of gas-fired power plant emission reduction timelines and lift caps on existing emission levels if battery storage falls below 10% of State generation capacity

Allows large gas-fired generating units to exceed their existing emission limits during hours when dispatched by a regional transmission organization for emergency, pre-emergency, or conservative operations, or when required to maintain system reliability

Requires the Illinois EPA to adopt implementing rules by July 1, 2026