Simulation of direct and diffuse solar radiation transmission into a lean-to greenhouse with photovoltaic cells on the roof and with infinite longitudinal length was conducted using mathematical models by Kozai. The effects of area percent (0-100%) of photovoltaic cells on the roof, greenhouse orientation (E-W, E-W ±15°and E-W±30°), north latitude (25, 30, 35, 40 and 45°) and season (winter solstice, spring/autumnal equinox and summer solstice) on the diurnal time courses of averaged transmissivity for direct solar radiation on the floor surface, and the cross-sectional distributions of transmissivity for daily integrated global (direct+diffuse) solar radiation on the floor surface were analyzed. When the area percent of photovoltaic cells on the roof was lower than about 60-80 in the winter, 40-60 in the spring/autumn, or 30-50 in the summer at the north latitude of 25-45°, the reduction and unevenness of averaged transmissivity for daily integrated solar radiation on the floor surface due to the shade by the photovoltaic cells were not significant for a greenhouse with orientations of E-W, E-W±15° and E-W±30°. Thus, notable amounts of electricity can be generated using photovoltaic cells without significant reduction in solar radiation transmission, if the area percent of photovoltaic cells and greenhouse orientation are chosen properly at a given latitude (geographical location) and time of the year.