Momentary reserve with BESS: New revenue stream in FTM operation

The marketing of Current reserve is developing into a new, stable revenue stream for operators of battery energy storage systems (BESS). Especially in Front-of-the-Meter (FTM) Operation enables them to generate additional revenue – without impacting existing business models such as Control energy or Power trading to significantly restrict. Since the end of January 2026, it will be procured on a market basis by the four German transmission system operators (TSOs) and can thus increase the overall return of a BESS without significant capacity conflicts.

This makes moment reserve another element in the Revenue Stacking, the combination of multiple revenue streams to maximize the economic efficiency of large-scale storage systems.

What is the moment reserve?

To ensure grid stability and prevent blackouts, the German electricity system must maintain the frequency at a constant 50 Hz (± 0.2 Hz). If the frequency deviates, the balancing energy market intervenes. This includes primary control power (FCR) for rapid stabilization, automatic secondary control power (aFRR), and minute reserve control power (mFRR) – however, these control services require time to react. This is where instantaneous reserve comes in.

Momentary reserve is a non-frequency-related system service that balances short-term power imbalances in the grid. The reserve is replaced by primary control power within a few seconds. Traditionally, conventional power plants automatically provided this service via their rotating masses—free of charge and without compensation.

With the decline of conventional power plants as part of the energy transition, there was a need for action. The Federal Network Agency therefore developed a concept for market procurement in April 2025, and since January 22, 2026, there has been a new, remunerated market for this in Germany.

How do BESS operators earn money from operating reserve?

While conventional reserve energy remunerates the provision of capacity (+/-) as well as the actual delivered and withdrawn grid power, instant reserve exclusively rewards Provision of performance capacity.

Until 2026, there was no standalone market for this in Germany. In Great Britain, lucrative products have already emerged in the context of FFR (Fast Frequency Response), such as Dynamic Containment (DC). In Germany, there were previously only bilateral contracts with network operators or special innovation tenders for this. The new German market now offers the following advantages for BESS operators:

1. Fixed price remuneration for capacity retention

From 2026, current reserves in Germany will be market-based by the Transmission system operator procured. Operators receive:

• Fixed remuneration per megawatt-second (MWs) of capacity provided
• Monthly billing
• Contract terms of up to 10 years

The following revenues are anticipated:

A perfect addition to revenue stacking

A key advantage of the instant reserve is that it brings hardly any operational limitations for other business models of a BESS. In contrast to classic grid reserve products or electricity trading, almost no active energy shifting is needed. Instead, the performance is based on the very fast response capability of the power electronics.

This makes reserve time an excellent additional revenue stream within the framework of Revenue Stackings. Existing marketing strategies such as:

• Primary Control Reserve
• Asymmetric Balancing Energy (aFRR)
• Electricity Trading (Intraday / Day-Ahead Arbitrage)

remain fundamentally unaffected and can be continued in parallel.

Crucial here is a powerful energy management system (EMS), which coordinates the various markets and ensures availability. This helps to avoid potential conflicts of use and to specifically optimize the overall economic efficiency of the storage.

3. Low load on the storage system

Since the moment of reserve is primarily provided by the inverter's power and requires hardly any full charging and discharging cycles, the impact on battery aging is small.

For operators, this means:

• additional revenue without relevant degradation
• no significant impact on lifespan
• Stable addition to cycle-based business models

The utilities notice that a 100 MW/100 MWh storage system only needs to hold around 35 kWh of energy. This is a clear economic advantage, especially when compared to intensive electricity trading or frequent grid balancing calls.

Technical requirements for participation

To provide instantaneous reserves, battery storage systems must meet certain technical requirements, which are not insignificant.

Grid-Forming as a Central Requirement
The provision of instantaneous reserve requires grid-forming inverters (Grid-FormingOnly these systems are capable of actively contributing to grid stability and simulating the necessary inertia.

In contrast, conventional (grid-following) inverters merely follow the existing grid signal and cannot provide instantaneous reserve.

Brief overview:

Further requirements at a glance:

• Pre-qualification by the transmission system operators
• The grid connection must be at least at the medium voltage level.
• Integration into a virtual power plant or control system
• Fully automated operation and fast responsiveness
• Ensuring defined availability levels (e.g., >90% % for the premium product)

Classification in FTM Operation

I'm FTM operation The Momentanreserve currently leverages its strengths particularly well, as it can be combined almost effortlessly with the other FTM applications of a BESS.

Currently, a reserve complements this strategy meaningfully, as it:

• regardless of fluctuations in electricity prices
• No active storage operation is forced
• creates additional planning security

This creates a stable counterweight to volatile revenue streams like electricity trading.

Risks & Market Development

Despite the attractive prospects, there are some factors that operators should consider:

1. Regulatory uncertaintiesThe market design is based on current regulations by the Federal Network Agency and may change in the future.
2. Market saturationSince BESS are technologically ideal for ancillary services, a strong market uptake could lead to declining compensation in the long term.
3. Multi-Use ConflictsIn cases of very high availability requirements, conflicts of use can arise with other revenue streams—especially without optimized energy management.

Conclusion: Inertia Reserve as a Strategic Revenue Component

Momentary reserve is developing into an important component of modern BESS business models.

For operators, it offers:

• additional, stable income
• low technical burden
• High compatibility with existing strategies

In FTM operation, it significantly contributes to Optimization of overall profitability especially in conjunction with balancing energy and electricity trading.

In the long term, it should be seen less as a sole revenue driver, but rather as valuable building block in the overall portfolio of a battery storage system.

Frequently Asked Questions