Add to ORKGThis study deals with the increase of power imbalance and its related cost due to the growth of solar penetration. We applied state-of-the-art day-ahead solar and load forecast models to predict residual load of Italy. Using these models and real data provided by the Italian TSO, we suggest and test different imbalance mitigation strategies and we compute the resulting imbalance volume and cost at different PV penetration levels. We show how the imbalance can be set to a fixed value regardless of PV installed capacity, allowing for a massive solar penetration. The strategies consists in: (1) Improving the accuracy of PV and residual load power forecast (2) Enlarging the footprint of the forecast controlled area; (3) Implement PV imb...