This paper presents a new simple and effective method to extract the loss parameters of solar panels/solar cells and accurately represent their electrical behavior. This approach allows the extraction of the parameters of the single diode model using only the information provided by the manufacturer’s data sheet. The proposed method presents a computational procedure of low complexity, which makes it possible to estimate the five parameters of any photovoltaic or generator cell. Using the complete equation of the single diode model, the number of parameters to be calculated is reduced only to two parameters by an equation exclusively connecting the series resistance and the diode current. Suitable validations on important case studies are presented, an experimental data from multi-crystalline MSX120 and thin film NA-F135 solar panels were used to test the single diode model with the extracted parameters. The experimental data are first collected at the same temperature at two different irradiance levels and at a low irradiance level at a fixed temperature for MSX120. In the second stage, variations in temperature are considered at different irradiance levels for NA-F135. The extraction results show that the I–V curves accurately fit the entire range of the experimental data. In addition, the results of the proposed procedure are compared to the most recent proposed techniques in literature. Furthermore, the results obtained are highly accurate; in particular, at maximum power point the error is always less than 0.005%, which is quite far from the authorized error of 1%.