Climate change is a pressing issue and risk in our current society caused by greenhouse gas (GHG) emissions. To reduce the GHG-emissions more renewable energy is needed instead of electricity and energy production by fossil fuels, which are high in GHG-emissions. The electricity production by renewable sources has increased in the last couple of years in the Netherlands. However, renewable energy production via wind and solar energy is supply based, i.e. can only be supplied when wind and sun is available. Energy storage is needed to overcome the energy needs during low or no renewable energy in sustainable way. However, there barely seems to be any storage in the Netherlands. The market does currently not value all the services that storage can provide. Research into the value of storage is needed to understand the lack of energy storage and the current valuation of energy. Energy storage can have different levels and services that it can provide. In this thesis the focus will be on grid-scale energy storage. In the Netherlands there are no grid-scale energy storages. In other countries there are grid-scale energy storages, often in the form of Pumped Hydro Storage. In the Netherlands there is a plan, called Delta21, that wants to expand the Delta Works and improve water safety by using pumps. In the plan the pumps can also be used for a Pumped Hydro Storage to store energy. It is important to understand the value of storages like Delta21 in the Dutch electricity system.