Global solar radiation data are essential in the design and study of solar energy conversion devices. In this regard, different empirical models based on Angstrom-Prescott model were selected to estimate the monthly average daily global solar radiation (H), on a horizontal surface using sunshine duration, relative humidity and temperature. The selected models were compared on the basis of the statistical error tests such as the mean bias error MBE, the mean percentage error MPE, the root mean square error RMSE, Nash-Sutcliffe equation NSE, correlation coefficient r, coefficient of determination R^2 and the t-test t. The present book will help to advance the state of knowledge of global solar radiation to the point where it has applications in the estimation of monthly average daily global solar radiation.