A stand-alone photovoltaic power system is designed to operate residential appliances such as fluorescent lamp, incandescent light and ceiling fan using standard methods. The total load is estimated for four hours of operation per day. The battery is sized considering different factors that affect battery efficiency to reliably operate the estimated loads during a sequence of below average insolation. The minimum battery size is obtained to be 128Ah @ 100 hr, 24V. The PV array is sized to operate the load on a daily basis based on average weather conditions using monthly average daily values of solar radiation data for 11 years. The array is sized to proper values in order to operate the estimated load reliably in the month of minimum insolation taking into account different types of power losses. The minimum array size is obtained as 6 x 47W(p) (C) 2002 Elsevier Science Ltd. All rights reserved.