How does a schedule freeze influence German BESS revenues?
German grid operators are struggling to manage the flexible assets joining their networks. Flexible connection agreements (FCAs) have become an almost catch-all response to prohibit possible negative impacts of BESS deployment on grids - restricting full flexibility by introducing ramp rates, import/export caps or ancillary service limits.
Germany’s TSOs are proposing a "schedule freeze": a rule that would stop batteries from changing their trading positions within a certain time before delivery. For BESS, that is effectively an earlier gate closure, with proposed windows ranging from two hours before delivery up to 18:00 on the day-ahead.
That window happens to be where almost all of the intraday revenue lives. It is also where Germany's renewables increasingly look for a counterparty to balance their position before delivery. The freeze is being framed as a grid stability measure. In practice, it is a design choice. If implemented at a large scale, it could reshape BESS business cases, intraday price formation, and redispatch and balancing costs from 2028 onwards.
In Modo Energy's Apr-26 forecast, batteries lose roughly 92% of their intraday revenue if they cannot access the continuous intraday market. Even after compensating in the day-ahead market, this results in a 20% reduction in total BESS revenues. But if a more lenient schedule freeze applies or the rule applies to every new TSO-level battery and BESS build their own liquidity peak three hours out, the hit could narrow to an estimated 50% of intraday revenues.
Key takeaways
- A blanket D-1 18:00 schedule freeze removes around 92% of BESS intraday revenue. After day-ahead substitution, total BESS revenues fall by roughly 20%.
- Renewables lose their natural late-window counterparty. Evening forecast errors approach 20% of generation, so without BESS to absorb them, price spikes and imbalance costs land on users' bills.
- Freeze length matters less for BESS revenues than for system stability. A 2h, 3h or 4h freeze all produce a similar revenue hit based on the missed traded volumes and volatility. What differs is whether liquidity clusters cleanly at one point or smears across the post-gate window.
- A funnel-style alternative could thread the needle. By committing capacity progressively rather than all at once, the design preserves some late-window liquidity for renewables. TSOs still get most of the redispatch certainty they want.
What is a schedule freeze, and why is it needed?
Generators, loads, and BESS submit schedules to the grid operator outlining their plans. They usually submit an initial schedule after the day-ahead auction, then update it based on new forecasts or positions taken in other markets. TSOs use these schedules to model flows and plan power routing.
Batteries can react very quickly to intraday signals. Intraday signals can be unpredictable, and batteries have the technical ability to move their schedules vehemently across the continuous market, sometimes minutes before gate closure. That can become a problem for TSOs if tens of GW of BESS do this simultaneously.
To maintain grid stability and handle internal bottlenecks through redispatch, TSOs need time to:
- calculate load flows
- work out the best redispatch
- instruct market participants
- most crucially, to adjust cross-border flows, which requires European alignment of closures.
Now imagine a grid with tens of GW of batteries on the TSO level, all switching on intraday signals within minutes of delivery. TSOs have to react within minutes, changing redispatch and reorganising flows internationally and locally.
Other markets have similar problems - and solve them with better signals for market participants. In Germany, the proposed answer is a schedule freeze. BESS would not be allowed to change their schedule within three hours of delivery. In effect, this is a three-hour gate closure for batteries.
Why it matters: Intraday markets are concentrated close to delivery
BESS currently earn strong revenues in the continuous intraday from two sources:
- Readjusting positions based on new signals and more extreme intraday prices as delivery approaches
- Re-trading positions several times, so-called non-physical trading, or churn
Most intraday trading happens close to delivery. The reason is simple. Wind and solar update their generation forecasts throughout the day and need to balance themselves in the hours close to delivery. That is where most of the volume is actually traded.
Not just the traded volume increases close to delivery. As conditions become clearer and more trading happens, both outright prices and price volatility move. Based on data from the first quarter 2026:
- Prices move further away from the day-ahead price close to delivery. In the final 15-min window before delivery, the standard deviation compared to day-ahead prices is €59.22/MWh. 3h before delivery, its €30.55/MWh, 10h before delivery it’s €21.71/MWh.
- As more and more volume is traded, the intra-hour liquidity also rises. The price of all trades in the last 15-minute period before delivery has a normalised standard deviation of 7.2%, compared to 1.2% 3h before.
This is exactly how a battery makes money - smoothing out intra-hour volatility and counteracting squeezes by being available on the other side of unexpected supply or demand shortfalls.
What the freeze does to BESS revenues
In Modo Energy's Apr-26 central case, removing BESS access to the continuous intraday cuts intraday revenue by roughly 92%. This would be the case for an extreme cutoff point, such as 18:00 on the day-ahead, which completely stops the battery from any continuous intraday trading.
