The knowledge of irradiation in a geographical area is very important for multiple areas for the development of the area. Current calculation systems are based on statistical models of measurements of ground stations, or by external radiation calculations by satellite models. In this paper we show another method of calculation, based on the estimation of the incident radiation in a geographical area, through the production of electric energy generated by known photovoltaic solar installations. With the data of several years of three installations with equal inclination, model of solar panels, and in the same geographical area, the island of Fuerteventura, in the Canary Islands (Spain), we perform monthly irradiation calculations based on the total production of each month. With the calculated irradiation data, we performed a statistical study of them, using the ARIMA model with the SPSS Statistics software and we also carried out the study using a Fourier series decomposition model. With the two models, we made a comparison by measuring the forecast errors with the indicators of the root-mean-square error (RMSE) the mean absolute percentage error (MAPE) and its regression coefficient R2. We verify the validity of the method shown for both statistical models of irradiation prediction and verify that the best results are obtained for the Fourier decomposition model. © Research India Publications.