Reservivoimaa

Reservivoimaa, or reserve power, is the extra electricity capacity or demand response that can be mobilized quickly to maintain the balance between electricity generation and consumption and to sustain grid reliability. The term is used in Finnish energy discourse to describe services contracted to the transmission system operator (TSO) for operating reserves and balancing.

Reservivoimaa can be provided by several sources: conventional power plants with spare capacity, fast-start units such as gas turbines, energy storage installations (batteries, pumped hydro), and demand-side resources capable of reducing consumption temporarily. It is procured and compensated through ancillary services markets or capacity contracts, and is activated when actual generation or import falls short of forecast demand or after a disturbance is detected.

Typical categories of reserve power include spinning reserve (online generation that can increase output with little notice), non-spinning reserve (offline plants that can start within minutes), and replacement reserve (capacity kept to replace other reserves after they have been used). Some grids also define voltage support reserves and other category-specific services. The system operator monitors reserve margins and requires them to be available at predefined levels to cover contingencies.

With higher shares of intermittent renewables, the role of reservivoimaa has grown, emphasizing flexibility across generation, storage, and demand response. Effective management depends on timely forecasting, communication between market participants, and adequate payment for reliability services.