2026 Variable operations and maintenance cost review

Through this recurring triennial stakeholder process, the California Independent System Operator (ISO) will review the default variable operations and maintenance (VOM) adders and update these values as needed. The ISO will also introduce a new default value for the variable storage operations cost.

The VOM adder allows market participants to reflect their variable operations and maintenance costs in market bids. The ISO incorporates these adders into a resource’s proxy costs, which align with the three bid components used in the energy markets: default energy bids (DEBs), minimum load costs, and startup costs.

The variable storage operations cost allows market participants to reflect the variable cost of operating their battery storage resources in market bids. The ISO incorporates this adder into a resource’s storage default energy bid, and potentially into the negotiated DEB.