The present article deals with the employment of combined heat and power (CHP) micro gas turbines using natural gas and cold thermal energy storage system (CTES) in Tehran (with mild climate). Bandarabas (with hot and humid climate) and Kerman (with semi-hot climate). A micro CHP produces electricity to meet the electrical energy needs of the building, and it is also considered to meet part of the heating, cooling and domestic hot water energy needs through a heat pump and refrigeration system. A detailed study considering the effect of CTES system on the selection of micro gas turbines of a residential building located in Tehran is performed. The results show that since the number of micro gas turbines is dependent on the maximum cooling load required in the summer using CUES system reduces the CHP micro gas turbine units from 21 to 11 and costs from US$ 1,133,221 to US$ 799,061 (29.5% economical) for the residential building which is located in Tehran. Also, using this system in Kerman and Bandarabas reduces the micro CHP gas turbine units from 21.75 to 11.40, respectively. (C) 2010 Elsevier B.V. All rights reserved.