ERCOT RTCB Go-Live: Key Market Changes Starting Dec. 5, 2025

ERCOT’s Real-Time Co-Optimization (RTCB) goes live on Dec. 5, 2025, bringing the most significant front-office updates since Nodal launch. Below is a clear rundown of what’s changing and why it matters as we move into cutover week. 

If you need a refresher on what RTCB is and why it matters, check out our earlier post “What Is RTCB & Why Does It Matter for ERCOT?” 

What’s new with the ERCOT RTCB go-live? 

1. COP status overhaul 

RTCB completely restructures COP status handling for Generation Units, ESRs, and Load Resources. 

• A large group of legacy statuses is being retired — including ONREG, ONDSR, ONOSREG, ONDSRREG, ONRR, OFFNS, FRRSUP, FRRSDN, ONFFRRRS, ONECRS and others. 

This cleanup streamlines COP statuses and aligns with the new Energy and AS co-optimized operations. 

2. Update RT Three Part Offer requirements 

RTCB also updates how Real-Time Three-Part Offers must be submitted. When you adjust an RT TPO in the current or next hour, ERCOT now requires: 

• Reason Code = “OTHR” 

• Reason Text is required (any short explanation is fine) 

These changes help ERCOT clearly distinguish true real-time operational adjustments from standard forward-looking updates. 

3. Real-Time AS awards & AS prices 

RTCB introduces true Real-Time Ancillary Service awards and pricing because AS is now fully co-optimized with energy in SCED. This means: 

• RT AS Awards are feasibility-based and can change throughout the day as system conditions shift. 

• RT AS Prices are now produced directly by SCED, giving the market real-time AS price signals for the first time, instead of relying on Day-Ahead values. 

RTCB moves AS from a once-a-day construct to a fully dynamic, real-time product. 

4. AS Trade Overage Report (new daily compliance check) 

RTCB adds a new daily report that’s worth paying attention to. The AS Trade Overage Report, posted at 14:30, flags any hour where a QSE’s purchased Ancillary Services exceed their Self-Arranged quantities.  

When that happens, the excess becomes a new settlement exposure under RTCB. It’s a simple report, but one that can trigger unexpected charges if not monitored closely. 

5. Day-Ahead AS-Only Offers (ASOO) 

RTCB also introduces the AS-Only Offer (ASOO) in the Day-Ahead Market. This instrument can be submitted by AS type, and is validated the same way as offers from an online resource.  

ASOO doesn’t replace standard AS offers — it just gives QSEs another flexible way to participate in AS market without having a physical resource.  

6. Single-Model ESR transition 

RTCB fully migrates batteries to the Single-Model ESR design. This is one of the most impactful changes for storage operators. 

Key updates include: 

• One unified device from negative LSL (charge) to positive HSL (discharge) 

• A single monotonic EB/OC curve across the full range 

• Up to 10 price/quantity pairs 

This eliminates the dual-model structure and simplifies integration across ERCOT systems. 

What’s changing with the ERCOT RTCB go-live? 

1. AS Responsibility now becomes AS Capability 

Under the old rules, you could manage AS at a portfolio level: 

• QSEs had to calculate their AS Responsibility based on DAM awards, self-arranged quantities, trades, infeasible AS reallocations, and SASM awards 

• You then had to submit that responsibility back into the COP 

Under RTCB: 

• SCED awards AS based on unit-level feasibility, duration, SOC, telemetry, and ramp 

AS Capability gives ERCOT a real, physical, hour-by-hour view of each resource’s ability to carry AS under RTCB. 

2. AS Obligation reports 

RTCB introduces two new daily reports replacing the old AS obligation structure: 

• AS Obligation Advisory (posted by 06:00) 

• AS Obligation Final (after DAM) 

The obligations themselves haven’t changed — the Advisory report simply replaces the old version, and the Final report is now issued after all QSE inputs are processed in the DAM. 

3. AS and energy price caps 

RTCB maintains current price caps, but they are now enforced consistently across both energy and ancillary service submissions: 

• $5,000/MWh – Day-Ahead SWCAP 

• $2,000/MWh – Real-Time SWCAP 

4. Workflows retired under RTCB 

Several legacy market constructs are discontinued: 

• SASMs eliminated 

• FRRS Up & FRRS Down removed 

• Non-Spin $75/MWh TPO price floor eliminated 

• RT Energy Bids for CLR-side batteries discontinued 

These removals streamline market operations and reflect the new RTCB architecture. 

Final thoughts 

RTCB introduces significant updates across energy clearing, AS processes, COP handling, and ESR operations. These adjustments will shape day-ahead and real-time workflows going forward and reflect ERCOT’s evolving approach to operational feasibility. 

For deeper guidance, explore ERCOT’s official documentation or use our RTCB Bot for quick answers. Staying informed now means fewer surprises — and better results — when RTCB goes live.