The electricity supply will become more volatile in energy systems with increasing shares of Renewable Energy Sources (RES). Since electricity demand varies as does the supply by RES, the remaining residual load must be covered by flexible technologies that are required to balance the different types of fluctuations. In this study, these flexibility options are divided into three categories: increasing the residual load, decreasing the residual load and shifting the electricity demand / supply temporally or spatially. Furthermore, typical technological options are discussed for each category, and four flexibility criteria are used to compare their technical and economic characteristics. These include the activation time, duration of flexibility provision, number of activations and activation costs. The study reveals that various options exist and no one technology dominates. However, within the flexibility categories, it can be shown that some appliances have advantages in three of the four categories compared to the other options. Ultimately, the choice of the most appropriate flexibility option depends on the requirements of the energy system. It can be concluded that a mix of technologies will be needed to cover the future flexible demand that may include short-term changes of the residual load as well as long-term downturns of RES generation.