Abstract-Cogeneration systems and equipment suitable for residential and small-scale commercial applications like hospital, hotel or institutional building are available, and new systems have developed. These products are used or aimed for meeting the electrical and thermal demands of a building for space and domestic hot water heating. In last years cogeneration has played a significant role in Turkish energy strategy, with plans to satisfy the considerable portion of Turkey's requirements for electricity from cogeneration. The main purpose of this work is to supply the demand for electricity and heat for housing complex in Turkey.In this study, it is showed that cogeneration systems in housing complex are an extremely profitable investment for country and consumers. Here application of cogeneration on housing complex was made in Istanbul. It is stressed that this technology should be applied as an energy method in old and new housing complex.The aim of this paper is to maintain a study by using real consumptions of housing complex in Turkey. Electricity and natural gas consumption quantities have been obtained from housing complex. Finally as it is resulted from payback period approach the system is paid off itself in 1.33 year, approximately 16 months.