The purpose of the study is to assess if thermal energy storage (TES) in combination with heat pumps (HP) or electric boilers (EB) leads to increased flexibility and socio economic feasibility of energy systems with high share of wind. In the study two different systems have been analyzed; Eastern Denmark and the CTR transmission system. The calculation tools EnergyPLAN and EnergyPRO have been applied to analyze the two systems respectively. The two analyses show different results, and it is indicated that a model error is causing unexpected results of the EnergyPLAN analysis. Generally the results show that increased TES capacity is feasible to a certain limit which is extended when combining with an EB capacity. HP capacity in combination with TES will increase the system flexibility, reduced fuel use, but is generally not socio economically feasible.