Thermal storage tanks are important components in both, solar thermal as well as photovoltaic and heat pump systems, because they can bridge the time between production and demand of heat. For low exergy energy sources such as solar thermal collectors, heat pumps, and waste heat recovery, the stratification within the tank is of key importance for the efficiency of the system. In this project, existing recommendations for the design of stratified storages are generalized to any storage size. The deflection relation is identified as a relevant variable. If this deflection relation is less than 0.12 for vertical inlet and less than 0.5 for inlet via an upward or downward elbow pipe pointing towards the top or bottom of the tank, the unintended deflection of the entering fluid stream into local vertical flows is low and an existing storage stratification is effectively maintained.