The parameter extraction method of De Soto is implemented in the single diode model and evaluated against measured data at varying temperatures and irradiances. The simulated current-voltage-curves (IV-curves) of the method can be seen as acceptable at reference conditions, but they result in a different IV-curve, not matching the measured IV-curve, at conditions that differ from the reference conditions. To solve this problem an adjustment function is presented which improves the error that De Soto's parameter prediction makes in different environmental conditions. The relationship between this method's error to temperature and irradiance and the error De Soto's method makes is examined and presented as a percentage error to the measured data which is used as the reference. The adjustment function is optimised to fit the measured data.