The theory of waveguides induced by gray solitons in closed-circuit photovoltaic crystals is analyzed. The study shows that waveguides induced by gray closed-circuit photovoltaic solitons are only a single guided mode for all soliton graynesses and all values of both the electric current density and the ratio between the soliton peak intensity and the dark irradiance. The results explain that the confined energy near the center of a gray closed-circuit photovoltaic soliton increases with the electric current density and decreases with an increase in both the soliton grayness and ratio between the soliton peak intensity and dark irradiance. Relevant examples are provided where the photovoltaic crystal is assumed to be LiNbO3.