System Services Business Models for Solar Hybrid Power Plants and BESS

Industry News – October 3, 2025

According to figures from Ember, a think tank, photovoltaics (PV) became the EU’s primary power source for the first time in June, accounting for 22.1 percent. The increasing volume of renewable electricity in the system is driving the rapid development of the industry. The power grid is seeing a shift as renewable energy systems are increasingly having to handle critical functions necessary for its operation. Solar hybrid power plants (PV+BESS) as well as standalone BESS are able to provide system services that help keep the power grid stable. At the same time, this segment of the market opens up new business models that make PV+BESS / standalone BESS projects more attractive to investors.

What are system services?

System services are the services that are needed to ensure the reliable and stable operation of the electricity system, and of the electricity grid in particular.
System services cover the following functions:

  • Maintaining frequency stability (50 hertz):
    • Power system inertia (synthetic inertia, spinning reserve)
    • Balancing power
  • Maintaining voltage stability: Reactive power
  • Supply security/restoration of service: Ability to perform black starts, ability to function off-grid
  • Operational management/grid stability: Congestion management, redispatch

Across Europe, system services are mostly provided by transmission system operators (TSO) and distribution system operators (DSO). Different countries have different models for opening the market (public tenders, bilateral agreements) and technology integration (fossil/thermal power plants, PV+BESS).

Unlike capacity mechanisms, system services are about flexibly responding to changes in the power grid. In a system with a rising share of electricity from renewable sources, the importance of system services is increasing. This is because:

  • Intermittent energy sources lead to more volatility in the power grid, which means that stronger frequency deviations need balancing out.
  • Without conventional power plants, the physical inertia previously provided by synchronous machines no longer stabilizes the grid.

The adoption of system services by PV+BESS/BESS will, thus, be essential in determining whether an energy system that uses a large proportion of renewable energy sources can function. Renewable power plants without BESS are also able to provide system services, albeit to a limited extent: They can provide reactive power.

Markets for system services: Business opportunities for PV+BESS

Germany has several procurement and market schemes for system services, in which some hybrid solar power plants and stand-alone battery systems are already participating to some extent. However, the upcoming reform of these schemes will create new business models for these types of systems:

  • A market for balancing power
    Balancing power is the operating reserve that bridges the gap between the generation and the consumption of electricity, keeping the power line frequency at a stable 50 hertz. This market is managed through regelleistung.net, the platform for balancing services, Where transmission system operators procure balancing power through tenders. BESS already covers a small section of the balancing market: According to the company Synertics, an analysis of the data from regelleistung.net showed that the share of BESS in the prequalification volume for PCR was 18 percent in 2024.
  • A market for reactive power
    Reactive power is electrical power that does not perform any work, but is essential for maintaining voltage and grid stability. In Germany, until recently, reactive power was managed through bilateral agreements between major fossil-based and thermal producers and grid operators. With conventional power plants being taken off the grid, however, the number of suppliers is sinking fast. To adapt to the new situation, in 2025, Germany started gradually introducing a market-supported system for reactive power. This opens the door for renewable, decentralized producers, BESS and electrolyzers for the procurement of reactive power. Network operator 50Hertz launched an initial pilot project with a call for tenders in April 2025.
  • Market for power system inertia and the grid-forming characteristics of PV+BESS / BESS
    Power system inertia acts immediately to stabilize grid frequency within milliseconds of a disruption, making it a crucial system service. In the past, this service has been a by-product of the flywheel in large, conventional power plants. With conventional power plants being phased out, Germany is now creating a market for power system inertia, to be implemented by all four DSOs by January 2026.

The objective is to allow renewable/BESS capacities to participate in this market. The technical requirement is that the systems provide grid-forming functionality, which is possible if they are equipped with a grid-forming inverter.

The ability to perform black starts and the independent control of frequency and voltage will depend on the existence of a grid-forming technology, consisting of BESS and a grid-forming inverter. This will enable complex system services to be performed – replacing the services previously offered by conventional power plants. Germany undertook an important step towards this goal in 2024 and 2025 with the introduction of technical guidelines and standards (for grid-forming properties of inverters).

Economic impact on investors and plant operators

Some of the earnings of hybrid power plants using PV+BESS or standalone BESS are being generated through arbitrage transactions and the sale of electricity on the spot market. The income streams and the resulting system profitability therefore depend on volatile market prices. Arbitrage transactions provide a basis for investments while system services can boost the ROI on equity capital. System services offer the chance to diversify the yield from PV+BESS/BESS.

In some markets, such as the UK, projects integrate system service involvement with tolling agreements, allowing to combine fixed revenue from contracts with flexible market yields and system service earnings.

The introduction of markets for power system inertia and reactive power procurement will create new remuneration options for systems with grid-forming properties in Germany.

One such example is the market model for quick reserve, which was recently introduced in the UK. According to Cornwall Insight, a market research firm, the model has led to a five-fold increase of income streams from system services for BESS within the space of one year. Cornwall Insight is expecting the prices to fall, however, as battery capacity increases in the market becomes saturated.

Conclusion and outlook

Renewable energies will have to take on responsibility for the system – with battery storage systems and grid-forming inverters. In the future, system services will have to be provided by solar hybrid power plants or standalone BESS – and this opens the door to new business opportunities and paves the way to the healthy diversification of income streams for plant operators. At the same time, the ongoing development of grid-forming technology is proof of the fact that solutions for a 24/7 supply with renewable energy have reached market maturity, and that a speedy rollout is essential for the energy transition to succeed.

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