In this study, the authors propose a feedback control method for energy storage systems for storing electrical energy and for load levelling. The proposed method uses both source and load power feedback, resulting in a fast response with respect to load levelling. To verify the proposed system, a power conditioning system based on the proposed feedback scheme was implemented and tested, in order to show the effectiveness of the scheme with respect to load levelling and energy harvesting. The system involved 60 of 50 W photovoltaic panels and a 20 Ah lithium polymer battery. An office was selected for testing, which was performed over an entire year. The authors obtained the operating profiles and determined the reduction in the daily total energy usage of the consumer as well as the standard deviation in load levelling.