The European power system is transitioning toward a higher share of variable renewable energy sources. As a result, the task of ensuring power system balance becomes increasingly challenging due to the inherent variability and forecast uncertainty of these resources, highlighting the need for robust methods to assess and quantify system flexibility. This study explores how future balancing and flexibility needs can be assessed using the Balancing Tool Chain (BTC), a multi-stage modelling framework linking long-term planning, day-ahead scheduling, hour-ahead balancing, and real-time frequency control. By capturing interactions between forecast errors, dispatch decisions, and resource availability, BTC enables consistent analysis of future balancing challenges.

A case study of the Nordic power system for 2030 is conducted to quantify regional flexibility needs by comparing updated hour-ahead wind forecasts with day-ahead dispatch schedules. This approach identifies net imbalances and available regulation capacity across technologies and areas. The results highlight large regional differences in flexibility requirements, with hydro reservoirs providing stable balancing capacity, while wind-dominated areas face frequent uncovered needs and rely heavily on cross-border exchanges. The findings demonstrate the need and value of integrating balancing market modelling with long-term planning to support the electricity market development and system design.