Spectral irradiance distribution of the solar spectrum influences the output energy of photovoltaic (PV) modules under outdoor conditions. To evaluate this effect on PV modules, the spectral irradiante distribution should be represented by a zero-dimensional index because spectral irradiance distribution is one-dimensional data. The average photon energy (APE) is an index that represents the spectral irradiance distributions used for evaluating PV performance. Our previous study showed the uniqueness of APE calculated from 350 to 1050 nm wavelength and determined that the APE value uniquely describes the shape of the solar spectrum. In this study, several new indexes with multiple wavelength bands socalled APE(band) of solar spectrum were considered in calculations without using a whole range of the measured solar spectrum, allowing low cost measurements to be used for precise rating the output energy of PV modules under actual outdoor conditions. The result shows the uniqueness of new APE indexes to our previously reported APE calculated from 350 to 1050 nm wavelength (APE(350-1050)) and therefore, the APE(350-1050) can be expressed by the new APE indexes. To examine linearity of new APE indexes, their band-ranges have been changed within the short wavelength and long wavelength, and found that APE calculated using two wavelength bands ranges from 450 to 500 nm and 800450 nm was the most linear with respect to APE(350-1050). This indicates that the new index is reasonable for representing the spectral irradiance distribution and its effect on PV performance. To analyze this effect on output energy, we investigate the impact of APE on short-circuit current (I-SC) of different PV modules. The result showed that APE value changes the I-SC of PV modules, which in turn to conclude the possibilities of I-SC correction using APE index. (C) 2017 Elsevier Ltd. All rights reserved.