HI SB2739

Creates a mandate for electric utilities and electricity cooperatives to deploy grid-connected long duration energy storage systems capable of discharging at constant megawatt rates for six hours or more.

Requires utilities to submit annual deployment plans to the Public Utilities Commission by June 1 forecasting generation sources and overgeneration for five years ahead, with targets to avoid at least 60% of forecast overgeneration through long duration storage.

Establishes priority preferences for grid planning decisions: energy efficiency, renewables, and long duration storage receive first priority; transmission/distribution upgrades second; fossil generation third; and non-viable 100% renewables assets fourth.

Mandates PUC approval of all generation, transmission, and distribution contracts only after long duration storage has been considered as an explicit alternative with equal evaluation.

Requires storage to be "commercially viable" as determined by PUC, with utilities bearing financial risk if storage fails to meet performance commitments; does not restrict customer-owned behind-the-meter storage installations.