Energy storage technologies can assist intermittent solar and wind power to supply firm electricity by forming flexible hybrid systems. However, evaluating these hybrid systems has proved to be a major challenge, since their techno-economic performance depends on a large number of parameters, including the renewable energy generation profile, operational parameters of storage technologies and their associated costs. In this study, we develop a method to simulate the performance and determine the levelized cost of hybrid systems to provide firm electricity supply under various supply strategies such as peak demand and baseload at three different scales (representative sizes). The methodology is implemented for Switzerland, however, it can also be replicated for other geographies. Our results show that the optimal choice for a hybrid system depends on the scale rather than the supply mode strategy. We find that solar photovoltaics in combination with lithium-ion battery at the residential (0.39 to 0.77 EUR/kWh) and utility scale (0.17 to 0.36 EUR/kWh) as well as with pumped hydro storage at the bulk scale (0.13 to 0.18 EUR/kWh) offer the lowest levelized costs. Reducing the cost of both renewable and storage technologies as well as the storage size by allowing some level of curtailment or distortion in the firm supply profile improves the cost-competitiveness of hybrid systems.