In the hot climates, such as the northern African climate, where the ambient temperature is usually higher than the optimal Photovoltaic operating temperature in most times of the year, the efficiency of the Photovoltaic drops is significantly affected. There are several studies which have suggested different correlations to estimate the power output and the cell efficiency relative to the outdoor conditions in different environments; usually including parameters such as the ambient and cell temperatures, wind speed, total incident radiation, other meteorological parameters , material and system-related properties such as transmittance of the glazing cover. This report studies different correlation of estimating the power output and efficiency based on the cell s operating temperature discussed in literature while including wind speed and incident radiation to recommend a suitable correlation for the weather conditions in Cairo, Egypt.