The module according to the present invention is used for accumulating/drawing electricity in/from an electric accumulator (502); the module comprises first terminals and second terminals; the first terminals are adapted to be connected to a photovoltaic panel (501) and to an inverter (504), and the second terminals are adapted to be connected to the electric accumulator (502); the module comprises a conversion unit (503) adapted to be connected between the first terminals and the second terminals; the conversion unit (503) comprises, in turn, a two-way DC/DC converter (550) adapted to convert a first energy flow generated by the photovoltaic panel (401, 501) to store it in the accumulator (502) and a second energy flow drawn from the accumulator (502) to supply it to the inverter (504), the two-way DC/DC converter (450, 550) is configured to convert said first energy flow and said second energy flow in a selective manner. The module is characterized in that comprises: power detector means (507) adapted to be connected between a user arrangement (520), which comprises the inverter (504), in particular of the type with MPPT, and a user (506), and a public electric grid (508), and adapted to detect the power flowing between the user arrangement (520) and the public electric grid (508) and vice versa between the public electric grid (508) and the user arrangement (520); the conversion unit (403, 503) comprises a control unit (501) connected to the power detector means (507) and adapted to control the two-way DC/DC converter (550) as a function of signals generated by the power detector means (507). By means of such a module, it is possible to upgrade a photovoltaic system so as to minimize the electricity exchanges between the photovoltaic system and the public electric grid.