AZ HB4100

Requires municipal water providers with Central Arizona Project (CAP) water allocations to estimate the total cost per acre-foot of securing alternative water supplies if 100% of their CAP water becomes unavailable.

Mandates public notice to all customers by April 15, 2026 showing potential rate increases, including percentage increases by customer class and dollar amounts for typical residential bills.

Requires the notice to be distributed through three methods: mailed to all customers as a bill insert or separate mailing, published in a local newspaper, and posted prominently on the provider's website.

Applies to municipal providers receiving CAP water either through direct subcontracts with the Central Arizona Water Conservation District or through leases with other parties.

Contains an automatic repeal date of December 31, 2026 and is declared an emergency measure taking effect immediately upon passage.