In this paper, the importance of taking into account power losses in the design of sliding mode controller (SMC) for hybrid power source (HPS) has been investigated. The under laying HPS consists of a boost converter, a bidirectional converter, a photovoltaic (PV) panel, and a battery. Dynamic equations of the system are derived based on the state-space averaging method. Afterward, a method to obtain power losses is provided. A robust control methodology, based on SMC is then proposed to take the power losses into account. Asymptotic stability of the proposed method is ensured, using the Lyapanov stability theorem. To verify the robustness properties of the close loop system, with respect to the input voltage variation and load resistance, some simulations studies are presented and discussed. The experimental results, by implementation on SPARTAN XC3S400 chip, are also given for justification.