We have been developing technologies for energy saving in the residential sector. Recently, we have been concentrating our resources specifically into the development of polymer electrolyte fuel cell (PEFC) cogeneration systems. The system has excellent energy saving characteristics. However, the total amount of energy saved depends on how the system is operated. The characteristics of residential energy consumption are more complicated than in industrial use and depend on individual living patterns. It is therefore not easy to develop a control method for a system that can be generally applied across a wide variety of residential use. In this paper, we propose a system configuration and operation planning method developed for a residential PEFC cogeneration system. Using an operation planning method we developed, we demonstrate that our system provides higher energy savings than the conventional method. The energy saving rates are 15.9% under a large heat demand, 18.4% under a relatively high electrical demand and low heat demand, 1.3% under relative low electrical and heat demands. (C) 2009 Elsevier B.V. All rights reserved.