The basic resource of all solar systems is the sun, and a knowledge of the quantity of the energy available is of prime importance. Although the solar radiation outside the atmosphere is known and almost constant, various climatic factors cause wide variations in its value on the earth's surface. In addition, the relative position of the sun with respect to local points of interest will allow surfaces with different orientations and tracking ability to receive different quantities of solar energy. This research focuses on the effect of cloud cover on the solar radiation received on the earth's surface and presents computer models that calculate its value for the best system configuration. Then a complete assessment of the electrical output of such a system is given. With this purpose in mind, two solar resource evaluation models have been developed; the first method is based on a direct statistical approach correlating clear sky total daily radiation with measured daily insolation. This approach has been applied to a few selected sites and offers the procedure for extending the same coefficients to other sites with similar weather patterns. This model has been tested for six sites in Bangladesh . These sites are located around a "reference" site . The predictions made have shown to be quite accurate. The second model uses an analytical approach that combines clear sky methods with "correction" factors which are based on long term recorded solar ra- diation. In addition, this model has been enhanced by an algorithm that selects the optimal surface orientation that maximizes solar output. Finally, the hourly electrical output of the photovoltaic system is calculated after accounting for the various losses. This is presented as part of a complete solar energy evaluation model. / M.S.