A battery storage system is not a generation asset with one revenue stream, but a flexibility asset with many. The art lies in combining several markets and applications so that revenues add up without blocking each other. That is exactly what revenue stacking is — and it determines the bankability of a project.
The relevant markets at a glance
Arbitrage (day-ahead and intraday). The storage buys electricity in cheap hours and sells in expensive ones. With more than 500 hours of negative electricity prices in Germany in 2025, the structural opportunity is large — the volatility between price peaks and troughs is the actual raw material of storage.
Frequency containment reserve (FCR). FCR was the entry market for German storage systems for years. Prices are under pressure because substantial storage capacity has entered the market — FCR alone barely carries a project today.
Secondary and tertiary reserve (aFRR, mFRR). Higher prices than FCR, but more energy throughput and stricter requirements on availability and control. For many projects the most attractive balancing market.
Peak shaving and industrial applications. In behind-the-meter projects, the storage reduces load peaks and thus grid fees. The saving depends on the load profile of the industrial site — and can be a viable business model on its own.
Tolling and floor structures. Instead of marketing the flexibility itself, it is “rented” to an optimizer: for a fixed tolling fee or a guaranteed minimum revenue (floor). Often decisive for debt financing because predictable cash flows are created.
Indicative classification of the markets
| Market | Mechanism | Characteristics (as of 2026, indicative) |
|---|---|---|
| Day-ahead/intraday arbitrage | Spread between price hours | Growing with volatility; site- and strategy-dependent |
| FCR | Capacity reservation, symmetric | Prices under pressure, high competition |
| aFRR | Capacity + energy, asymmetric possible | Attractive prices, higher technical requirements |
| Peak shaving | Grid fee reduction | Individual per load profile; strong with high peak loads |
| Tolling / floor | Fixed remuneration from optimizer | Predictable, bankable, lower upside |
All revenues are indicative and depend on location, system design, marketing strategy and market development. They do not constitute a yield commitment.
What good stacking requires
Capacity is the bottleneck, not the number of markets. Every capacity reservation for balancing services is temporarily unavailable for arbitrage. Good optimizers switch between markets on a daily basis instead of committing statically.
Degradation is the price of energy throughput. More arbitrage cycles mean more wear. The marginal revenue of an additional cycle must exceed the degradation costs — otherwise stacking destroys value instead of creating it.
The grid connection limits the strategy. A connection with restricted charge power or active power requirements changes the achievable revenues. Marketing strategy and grid connection therefore belong planned together.
Contract structures determine financeability. Banks do not finance hopes for arbitrage, but predictable cash flows. Shares of tolling or floor revenues in the total cash flow are often the prerequisite for debt financing.
Typical mistakes
The most common mistake is adding up the revenues of all markets in a single spreadsheet row — as if the storage could fully play everywhere at the same time. Serious business cases model the joint dispatch and deduct degradation, round-trip efficiency (RTE) and availability. Equally common: revenue assumptions from best-case years treated as a permanent state, without sensitivities for falling balancing prices or shrinking spreads.
Conclusion
Revenue stacking is not a spreadsheet trick but an operating model: markets, technology, degradation and contract structure must fit together. Projects that model this cleanly at an early stage achieve better financing terms — and more realistic expectations.