As the share of wind power increases in the power system, also the share of uncertain generation increases. This, in turn, increases the total balancing energy, real-time balancing power requirements and ramping of the balancing generation. In this study, the impact of wind power forecast errors on the real-time balancing need was investigated for different shares of wind energy (4–30%) in Finland and the Nordic region (comprising Denmark, Finland, Norway and Sweden). The size of the aggregation area of the net imbalances has an impact on the net imbalance volumes. The larger the size of the area is, the smaller the normalised net imbalance volumes are. In Finland, the impact of wind forecast errors on the net imbalance volumes and the largest net imbalances is almost two times as large as the impact of wind power forecast errors in the Nordic region. A shorter forecast horizon has an impact of similar magnitude both on reducing the net imbalance volumes and the largest net imbalances and on aggregating imbalances from large spatial areas. When day-ahead forecasts are not corrected intraday (ID) the impact on the net imbalance volumes and the largest net imbalances is twice as large as when ID forecasts are used.