IL SB3974

Establishes a standardized property tax assessment method for commercial energy storage systems in counties with fewer than 3,000,000 inhabitants, setting the cost basis at $496 per kilowatt hour of rated energy capacity

Calculates fair cash value by subtracting physical depreciation (based on a 25-year lifespan) from the trended cost basis, with a floor value of 30% of the trended cost basis

Exempts commercial energy storage systems from equalization factors applied by the Department of Revenue, boards of review, assessors, or chief county assessment officers

Requires commercial energy storage system owners to commission and pay for a metes and bounds survey of the property and obtain a separate parcel identification number for tax assessment purposes

Allows taxing districts to abate property taxes on commercial energy storage systems by majority vote, and provides that former farmland can return to farmland assessment status after system removal if returned to farm use