This paper presents a method to jointly determine the sizing and operation control of hybrid-PV systems. Hybrid energy systems use different energy sources such as solar and wind energy and diesel gensets. They are an economical option in areas remote from the grid. In this context the correct and cost-effective system sizing as well as efficient system operation are important. The problem becomes complicated through uncertain renewable energy supplies and load demand, non-linear characteristics of some components, and the fact that optimum operation strategies and optimum sizing of hybrid system components are interdependent. The outlined approach finds an optimum operation strategy for a hybrid system by carrying out a search through possible options for the system operation control. The search is conducted over some time period using estimated weather and demand data and long-term system component characteristics. The costing of the operating strategies is evaluated and component sizes are changed by the designed algorithm according to optimum search rules. As a result an optimum system configuration is chosen by the algorithm together with an optimum operation strategy for a given site and application requirement.