RTC+B Duration Requirements

One of the quieter, but more operationally important, changes coming with RTC+B is how ERCOT applies duration requirements for real-time Ancillary Services. On paper, this looks like a simple rule tweak. In reality, it injects a new layer of state of charge (SOC) constraints into every bidding and dispatch decision you make.

Below is a breakdown of what’s changing, and why it meaningfully complicates operations for storage.

With RTC+B, Ancillary Service (AS) duration requirements are changing. And, for all Real-Time (RT) AS bids/offers, duration requirements will be rolling and forward looking. This means that when a RT AS offer is placed, operators will need enough SOC for the length of the requirement, even though the offer is only for the next 5-minute interval.

This is enforced by telemetered SOC, so any offers that do not strictly follow the rules are subject to mitigation in SCED.

At a high level, this raises the value of SOC – and the opportunity cost of dispatch. Let’s walk through a few examples of how this change adds complexity.

[1] Your entire SOC is required to cover DA AS awards

If you have a DA AS award, or combination of awards, that would require your full SOC to cover in RT operations, any deployment or voluntary dispatch will lead to an imbalance charge in the next interval – and any subsequent intervals until you recharge or the relevant operating hour runs out.

Example:

Assume you have a 100MW x 2 hour battery and at 6pm you have DAM awards for:

• 50MW Non-Spin award x 4-hour duration requirement = 200MWh required 

To cover the 50MW DA Non-Spin position, you would need to have a full SOC and offer it entirely into RT Non-Spin in each interval of that hour. If you’re deployed — or if you discharge even modestly into RT energy — your SOC falls below what’s needed to offer the 50MW capacity in the next interval. That triggers an imbalance charge. And you’ll continue to incur imbalance every interval until you are able to recharge or the hour is up. This dynamic directly limits how aggressive you can be in RTM operations. A single interval of discharge can turn into multiple intervals of imbalance exposure, or you may end up forced to recharge at a price that’s higher than you’d like to avoid the imbalance exposure.

[2] DA awards inhibit RT bidding

Even if your DA AS awards do not require your full SOC to cover the position, they may still impact how aggressively you pursue RT energy or AS. Any dispatch that pulls your SOC below the duration requirement for that award will create imbalance exposure in the next interval — and that exposure persists until you recharge or until the award window ends.

Example:

Assume you have a 100MW x 2-hour battery and at 6pm you’re holding:

• 50MW ECRS award x 1-hour duration requirement = 50MWh required (if wanting to cover the DA ECRS position)

In order to cover the 50MW DA ECRS position, you need to reserve at least 50MWh of energy as well as clear 50MW of ECRS every 5-minute interval of the hour to avoid imbalance charges. In a scenario where RT energy prices spike, you can only discharge until you hit a 50MWh SOC before dipping below the duration requirement. If you discharge more than that your SOC will be insufficient to offer the full 50MWs of RT ECRS in the next interval. That triggers an imbalance charge. And as with the first example, you’ll continue to incur imbalance every interval until you recharge or the hour rolls off.

For every interval, operators have to decide whether it is advantageous to pay the imbalance to capture the RT energy price. It’s no longer “does this RT energy price look good?” but “does it look good enough to justify triggering imbalance and paying to recharge later?”

[3] Upcoming DA awards constrain what you can do in earlier hours

Even before the DA award window begins, these new duration requirements will force operators to calculate the tradeoffs. If you have an upcoming hour with a DA AS position, aggressive RT activity in the preceding intervals – or even hours – can leave you undercharged when the operating hour starts. That SOC shortfall will immediately translate into imbalance exposure.

Example:

Assume RT energy prices spike at 7:45pm, and you discharge 75MW to capture the opportunity. But you have a 50MW DA Non-Spin AS obligation beginning at 8pm.

Unless you recharge quickly — and at whatever price the market gives you — you won’t have sufficient SOC to cover the 50MW DA Non-Spin position in the first interval of the award hour. Any discharge decision in the hour leading up to an AS obligation needs to factor in both the time available to recharge and the cost of that recharge — otherwise you risk entering the obligation window in an imbalanced position before you’ve even begun.

[4] Even without a DA award, dispatch limits future RT energy and AS bidding

Even if you’re not holding any DA awards, dispatching any energy reduces your SOC and will naturally limit future RT AS and energy offers. 

Example:
Assume you have a 100MW x 2-hour battery, are at 25% SOC (50MWh), and at 6:05pm you want to offer the following:

• 50MW ECRS x 1-hour duration requirement = 50MWh required
• 12.5MW Non-Spin x 4-hour duration requirement = 50MWh required

If you clear either RT AS position and are dispatched, you’ll need to ratchet down your next-interval offers across both products – and you stay constrained until you recharge. For example, if you are down to 40MWh of stored energy by 6:30pm, your bids will be limited to 40MW in ECRS and 10MW in Non-Spin.

Across all these cases, three themes show up:

1. The value of SOC increases because every MWh determines what you can offer next.
2. Dispatch decisions carry more downstream consequences. The calculus is no longer just “do I like this price?” but “what does taking this price do to my battery capability for the foreseeable future?”
3. Imbalance risk becomes easier to trigger and harder to reverse – especially if prices don’t give you a cheap recharge opportunity.

This raises the bar for real-time optimization.

How Tyba is approaching optimization in this new landscape

RTC+B makes SOC and imbalance risk central to every dispatch decision. Our approach explicitly accounts for the way being dispatched — or voluntarily discharging into energy — affects both future AS bidding and potential RT imbalance exposure.

AS awards provide consistent revenue, but may limit your potential to capture higher-priced energy opportunities. Tyba’s optimizer continuously calculates the revenue-maximizing tradeoff between these competing pressures.

To operationalize these tradeoffs, it is important for storage operators to have a system that allows you to tailor to your approach to your company’s evolved risk policy:

• Strict Coverage: Always cover DA AS awards by (i) maintaining sufficient SOC and (ii) bidding/clearing in RT AS to avoid any imbalance exposure. 
• Flexible Coverage: Ensure SOC to cover DA AS positions, but allow flexibility to reposition in RT to energy and/or other RT AS products based on market conditions. 
• Dynamic Coverage: Allow more flexibility to deviate from the ‘strict’ or ‘flexible’ approaches based on the RTM market dynamics. This may expose you to higher imbalance costs, but allow higher upside from RTM volatility.

By embedding SOC value and imbalance risk directly into bidding and dispatch logic, Tyba helps operators capture the most value from every interval while avoiding unnecessary penalties — a critical advantage as RTC+B adds complexity to ERCOT operations.