A new model about output power prediction of PV module with various tilted angles and cell to cell distances has been proposed in this paper. Light intensity arrived on a solar cell could be changed by characteristics of PV module materials. Refractive indices, thickness and absorption coefficients of glass, EVA, solar cell and Backsheet are used to predict output. Also, the incident angle of light is changed 0 to 90[$^{circ}$] and cell to cell distances are 5, 10 15[mm]. Two types of light incident on a solar cell are considered which are direct to a solar cell and reflected from Backsheet. The intensity of the incident light directly into the solar cell is reduced through glass and EVA about 17.5[%] in theoretical way. It has an error of 2.26[%] compared with experimental result. The results for compare theoretical with experimental data is validated within the error of 6.3[%]. This paper would be a research material to predict output power when the PV module is installed outdoor or a building.