To establish the optimized capacity of power transformer, this paper proposed the total demand factor of power supply facility. For this purpose, it was measured and analysed the operating pattern of power supply acility Installed in the apartment. As a result, it is found that the demand factor of each facility is following that : i) In case of [Xlwer water suwly facility ; 47[%], ii) In case of waste water facility ; 44[%]. Also, it was analysed that the optimized total demand factor of power load is proper 42[%1 than 52[%] to lead the efficiency operation.ration.