A computer implemented method of estimating solar irradiance, the method comprising: constructing a reference irradiance set of tuples; constructing a reference predictor set of tuples, merging the reference irradiance set of tuples and the reference predictor set of tuples by matching numerical identifiers for a location for which a global horizontal irradiance exists in the reference irradiance set of tuples and the timestamp with the numerical identifier for a particular location in the reference predictor set of tuples and the timestamp to provide a reference data set of tuples; and estimating the global horizontal irradiance for a specific location and a timestamp by minimizing the least squares error between the reference predictor set of tuples and the reference irradiance set of tuples to provide a set of estimated global horizontal irradiance values for a specific location and timestamp.