It is an object of the present invention to suppress such a situation that electric power selling becomes impossible while the deterioration of supply power is prevented. The electric power selling system of the present invention comprises a solar battery 3 as a power generator, and a control unit 7 which is connected with the solar battery 3 and a distribution line and configured to convert output voltage of the solar battery 3 into variable voltage for electric power selling. The electric power selling system further comprises a transmitter 60 connected with the distribution line, said transmitter 60 being configured to measure voltage of the distribution line and to supply the control unit 7 with an instruction value obtained based on the measured voltage value. The control unit 7 is configured to convert the output voltage of the solar battery 3 into the voltage for electric power selling based on the instruction value.