The call for lower CO2 emissions has increased the integration of renewable energy sources in the electricity system. However, these intermittent sources do not follow the cycles of demand and are unpredictable in their nature. As the electrical system needs to constantly balance supply and demand, these renewable sources cause problems in the operations of the grid. Electrical energy storage is proposed as a solution for these issues. The research uses an optimization model to test the effects of energy storage on the operation of the electrical system. It shows that the development of storage can be beneficial in systems with a large amount of renewables. The value of storage is mostly dependent on the amount of renewables in the electricity system. Low amounts of renewables give too little opportunities to load while too much renewables give the storage only few periods to unload. Secondly, the value of storage is dependent on the amount of available transmission capacity. In some situations, investments in transmission can be replaced by investments in storage. As the transmission system operator (TSO) is responsible for system balance, he should have the possibility to choose between different investments and pick the optimal one.