Grid Storage California has one of the largest battery fleets in the world, but a new storage-market analysis says a meaningful share of that fleet is still being operated like a simple daily timer. Gridmatic's CAISO Storage Report, released in June and highlighted this week by Energy-Storage.news, found that 30 California battery systems could have earned about US$98 million more over the study period if they had matched the top-performing asset's capture rate. That number is not a claim that every battery can become the same project in the same node. It is a warning about execution. The report points to static bid curves, limited market participation, and narrow product strategies as reasons that batteries missed available revenue in CAISO's day-ahead, fifteen-minute, real-time, and ancillary-service markets. In a grid where battery capacity has grown to roughly 17.4 GW , optimization is becoming as important as cell cost. AI-generated image California's storage buildout is moving from a deployment race to an operating-performance test. $98M Estimated upside if the sample matched the top capture rate 30 CAISO battery systems in the study sample 2.3 GW Capacity represented in the reconstructed dataset 141% TBx capture rate for the Caballero battery What Gridmatic Measured CAISO does not make asset-level storage performance easy to read. Unlike ERCOT, California anonymizes public market data, which makes it difficult to connect bids, dispatch, and realized revenue back to named projects. Gridmatic tried to reconstruct that missing picture using public market inputs, regulatory filings, and a shadow-clearing engine for 30 battery energy storage systems representing about 2.3 GW of capacity. The performance spread was wide. Energy and ancillary-service revenue ranged from less than $1 per kW-month to more than $6 per kW-month . PV Magazine USA reported a fleetwide median of $2.67 per kW-month in the sample. Energy-Storage.news cited Gridmatic's finding that some systems earned less than $1 per kW-month while top performers exceeded $6 per kW-month, with a roughly $2 per kW-month median in the interview framing. The exact median is less important than the spread. Batteries with the same broad technology class and similar market exposure were not earning similar revenue. That points away from cell chemistry or inverter selection as the whole story. It points toward bidding strategy, availability, and market coverage. AI-generated image A grid battery's revenue depends on how accurately it prices stored energy across multiple market windows. The Top-Bottom Benchmark Gridmatic used a benchmark called TBx, short for top-bottom, to compare battery performance. For a four-hour battery, TBx measures the spread between the four highest-priced hours and the four lowest-priced hours in the day-ahead market. It is a simplified yardstick, not a perfect operating plan. Real batteries have losses, constraints, state-of-charge limits, congestion exposure, outages, and warranty limits. Even so, TBx gives owners a clear way to ask whether an asset captured the basic daily value that was visible in the market. Only five of the 30 studied batteries exceeded their TBx benchmark, according to PV Magazine USA's coverage of the report. The standout was Caballero, a 100 MW / 400 MWh system in Nipomo, California, owned by Alpha Omega Power and Fengate Asset Management, and optimized by Gridmatic. Caballero achieved a 141 percent TBx capture rate and earned 2.45 times the median asset's revenue per kW-month. That is the source of the $98 million figure. Gridmatic asked what the 30-battery sample would have earned if each asset had matched Caballero's 141 percent capture rate. David Miller, Gridmatic's chief commercial officer and author of the CAISO report, described the estimate as indicative rather than exact. Some batteries may not have had the same location-specific opportunity. Others may have had more room to improve. Why it matters Battery margins are no longer decided only during procurement. Once a project is online, the revenue gap between passive bidding and active optimization can become large enough to change project returns. Static Bids Are the Weak Point The report's most direct criticism is that many CAISO batteries still rely on static bid curves. PV Magazine USA reported that 20 of the 30 assets used a static Regulation Down bid curve in 75 percent or more of active months, and 12 maintained a completely static curve for all active months in the study. Thirteen of the 30 used static energy bid curves for at least half the study period. A static bid can work in a stable market. CAISO is not stable enough for that to be the default. Solar output, load shape, gas prices, congestion, outages, wildfire conditions, hydro availability, and neighboring-market imports can all change the value of stored energy. A battery that does not update its bids across the day-ahead, fifteen-minute, and real-time markets can miss spikes, charge at the wrong time, or preserve energy when the market is already offering a better use for it. This does not mean every project should chase every price interval. Battery operators must protect warranties, manage degradation, and keep enough state of charge to meet obligations. The harder job is to price those limits dynamically. A static bid curve turns operating discipline into inertia. AI-generated image Battery operators increasingly need market software, forecasting, and dispatch discipline, not only good hardware. The Revenue Stack Is Getting More Complex Energy arbitrage is only one part of the storage business. Gridmatic and Energy-Storage.news pointed to missed opportunities in real-time markets and ancillary services, plus a tendency among lower performers to focus on a single product. That matters because the best revenue stream for a battery can shift quickly. Regulation, spinning reserves, day-ahead spreads, real-time volatility, and resource-adequacy obligations can each dominate at different times. The academic literature is moving in the same direction. A June 2026 paper from Vincent Yinjun-Wang and Madeleine Udell modeled battery bidding under price uncertainty and found that rational operators may withhold energy without market power because scarce stored energy has option value. A separate July 2026 paper by Nicolas Eschenbaum examined shared bidding algorithms in Australia's National Electricity Market and raised competition questions when the same algorithm provider controls a large share of near-margin battery capacity. The common thread is simple: bidding software is now part of market structure. For CAISO, that creates a balancing act. Better optimization can make batteries more useful to the grid because assets respond more precisely to scarcity. Poorly designed or overly synchronized algorithms can also create new oversight problems. Storage is flexible, fast, and increasingly large. The rules written for generators with fuel costs and slower ramps do not automatically fit fleets of batteries making thousands of price decisions. Availability Still Matters Bidding is not the only reason revenue varies. Gridmatic's sample also showed that availability remains a real drag. PV Magazine USA reported average fleet availability of 79.7 percent, with downtime linked to hardware failures and safety incidents. Millikan Avenue reportedly had roughly 56 percent total downtime during the study period. Gateway was offline for 24 percent of the period, and Vistar's units at Moss Landing remained offline after a January 2025 fire incident. Availability and bidding compound each other. A sophisticated strategy cannot make money when the asset is unavailable. A healthy asset can still underperform if it bids like a fixed schedule. As California adds more storage, lenders and owners will need to treat operations as a full-stack discipline: thermal management, fire safety, warranty control, market forecasting, bidding, and compliance