Every Five Minutes, Texas Reprices a Battery
On December 5, 2025, ERCOT launched Real-Time Co-optimization plus Batteries (RTC+B), merging energy and ancillary service procurement into a single five-minute dispatch cycle. Batteries, previously modeled as two half-resources (one charging, one discharging), became single devices with state-of-charge constraints visible to the market operator in real time.
Three and a half months later, the consequences are becoming legible.
The old market. Before RTC+B, ERCOT procured ancillary services largely through day-ahead commitments. Battery operators could lock in reserve obligations, then arbitrage the spread between reserve payments and real-time energy prices. The strategy was straightforward: commit capacity to whichever product paid the most on a given day, hold the position, collect. Operators with decent forecasting models and fast settlement teams profited on inefficiency. The market rewarded those who could exploit the seams between products that were priced independently but consumed the same megawatt-hours.
The new market. RTC+B collapses those seams. Every five minutes, the system co-optimizes energy and reserves simultaneously, internalizing the opportunity cost of assigning a battery to one product instead of another. A megawatt-hour committed to Responsive Reserve is now priced against its alternative value in real-time energy, automatically, continuously.
The market monitor projects $2.5 billion to $6.4 billion in annual wholesale savings from the redesign, depending on how quickly participants adapt their bidding behavior.
The price signal shift. Ancillary service prices tripled in the period following implementation. Operators, suddenly exposed to real-time state-of-charge constraints during scarcity conditions, priced in that exposure. The movement likely reflects recalibration rather than permanent structural change. Operators who were parking capacity in a single product now face transparent opportunity costs; the market is learning what batteries are actually worth when those costs are visible.
Higher ancillary prices do not necessarily mean higher battery revenues. They mean the market is repricing risk that was previously invisible. Operators who earned margins by holding a single position will find those margins compressed. Operators who can dynamically shift between energy and reserves within the five-minute window will find new ones.
What changed for operators. The shift moves the competitive advantage from exploiting product design gaps to delivering flexibility precisely when the grid needs it. Before RTC+B, a battery operator could treat state of charge as a constraint to manage overnight. Now, the market operator sees it in real time and dispatches accordingly. A battery at 20% state of charge will not receive the same dispatch signal as one at 80%, even if both are offering into the same product at the same price. The algorithm knows what each resource can actually deliver over the next several intervals, and it acts on that knowledge every five minutes.
This creates a premium on superior telemetry, faster optimization algorithms, and a fundamentally different relationship with state-of-charge management. The winners under the old design were those who could forecast day-ahead prices well. The winners under RTC+B are those who can respond in real time.
Scale of the market. The US energy storage market installed 18.9 GW and 51 GWh in 2025, a 52 percent increase over 2024, according to Wood Mackenzie’s latest US Energy Storage Monitor. Wood Mackenzie projects 500 GWh of cumulative new deployments from 2026 through 2031, with annual installations potentially reaching 28 GW (base case) to 36 GW (high scenario) by 2031. ERCOT sits at the center of that growth. The market design that governs how batteries in Texas earn revenue is now fundamentally different from the one under which most of them were financed.
The broader question. If ERCOT’s implementation delivers on even the low end of the market monitor’s projected savings, pressure on other grid operators to evaluate similar co-optimization frameworks will intensify. The core design principle of RTC+B, that energy and ancillary services should be priced jointly rather than sequentially, is not specific to Texas. Any market where batteries participate in both energy and reserves faces the same inefficiency that co-optimization is designed to resolve.
For the commercial and industrial segment, the implications are indirect but real. RTC+B creates higher-value revenue streams for grid-connected batteries, which raises the financing floor for new projects and increases competition for the ancillary services that behind-the-meter systems can also provide through aggregation. In a market where battery deployment is accelerating at the rate Wood Mackenzie documented, the rules governing how those batteries earn their keep matter as much as the hardware costs.
Operators who built their businesses on ERCOT’s old market structure are now retooling. The ones who invested in real-time optimization software before December 5 had a head start. The five-minute clearing interval is not slowing down for anyone.
Sources
ERCOT Goes Live with Real-Time Co-optimization Plus Batteries (ERCOT)
ERCOT After RTC+B: How Real-Time Optimisation Is Reshaping Battery Storage Economics (Energy-Storage.News)
US Will Install 500 GWh of New Energy Storage by 2031, Wood Mackenzie Predicts (Energy-Storage.News)
US Energy Storage Installations Reach Record 51 GWh in 2025 (ESS News)