System Services: Everything You Need to Know

19 November 2025

1. What are system services?

System services – also called ancillary services – are the set of technical functions the electricity system uses to maintain normal, secure, and resilient operation of the grid. They make sure that electricity is always delivered safely and reliably, even when something unexpected happens.

For example, they:

  • Keep the frequency of the grid stable (so supply and demand stay in balance).
  • Control voltage levels to protect equipment.
  • Provide inertia, which helps the grid resist sudden changes of frequency.
  • Offer backup power or “reserves” in case a power plant or line fails.
  • Allow the grid to restart after a blackout (known as “black-start” capability).

2. Why are they important?

As more (grid-following) inverter-based renewable sources are integrated into the grid, a new challenge emerges: the grid is becoming less resilient to disturbances – on top of the need for upgraded infrastructure and increased capacity. Ensuring that this evolving power system remains reliable and secure requires a new focus on system services.

System services are the silent enablers of grid stability. They ensure that electricity flows smoothly, that supply and demand remain balanced, and that the system can recover from shocks or failures.

However, recent events, such as the Iberian blackout, have demonstrated how sudden disruptions — on either the demand or supply side — can threaten the entire system.

System services have traditionally been provided by conventional power plants. As coal and aging nuclear plants close and gas plants operate less frequently, these services are no longer guaranteed. Yet without them, the risk of blackouts or cascading failures significantly increases. This puts grid operators, who are in charge of ensuring the reliability of the grid, in front of a huge challenge.

3. What is the role of gas turbines in stabilising the grid and making it more resilient?

Turbine-based power plants have a key role to play in ensuring grid stability and resilience in Europe’s evolving power mix.

  • Gas turbines can start up, ramp up and down quickly, providing active power to balance supply and demand, especially when renewables fall short or there is a sudden disturbance.
    This capability helps to bridge the gap between intermittency of renewables and the need for continuous supply.
  • Turbines and generators in grid-connected gas power plants are spinning, providing high amounts of rotational kinetic energy. This keeps the frequency in the electricity system stable in case of unplanned sudden disturbances caused by e.g, a trip of other power generators or the disconnection of a large energy consumer. This inertia is of utmost importance for grid stability.
  • Gas and hydrogen power plants can be designed to run the generator as a synchronous condenser even in times when the turbine is not in operation. Decoupling the turbine from its generator by means of a self-synchronous clutch, the plant can provide the necessary grid services like inertia, spinning reserve, reactive power control and adjustable voltage control even when no active power is provided. Learn more about this here.
  • Modern gas turbines are being designed or retrofitted to co-fire hydrogen or operate with high hydrogen shares. This means they provide not just stability today, but a pathway to a decarbonised flexible generation fleet tomorrow. Thus, they can serve dual roles: supporting system services now, and supporting the energy transition (including coupling with hydrogen) into the future.

4. The policy & market dimension — what needs to change?

To ensure that system services are reliably available and adequately valued in the EU, several policy and market actions are required:

  • Recognition & value of system services: The EU energy security framework and market-design discussions must more explicitly include the importance of a smooth grid operation and the role of system services (inertia, reactive power, black-start capability, etc) in ensuring the resilience of the electricity system.
  • Energy system insurance: As Europe shifts toward more renewables and fewer conventional power plants, the cost of ensuring system reliability is rising sharply. System services act as an insurance policy for the grid—keeping it stable and secure. By remunerating these services, we reduce overall “insurance” costs and make the energy system more efficient.
  • Coordination across Europe and across time-scales: Because frequency, voltage and stability issues do not respect national borders, there must be coordinated frameworks and transparency across Member States and TSOs/DSOs.