costs for a specific value of an amount of energy the first prosumer p1 may both supply and absorb amounts of energy however the costs for supplying amounts of energy are very high because for example when amounts of energy are stored more energy is to be absorbed than may later be supplied thus a slope in the costs c between the values of the amounts of energy u2212 10 lt ex lt 0 is greater in absolute value than in the range of the values of amounts of energy 0 lt ex lt 20 in accordance with the exemplary embodiment see fig2 e 1 u2212 4 was assigned as the amount of energy to the first prosumer this results in the costs c 70 in partial figure b of fig4 a cost function is illustrated for the second prosumer p2 the prosumer p2 is a pure power generator that supplies amounts of energy in the band of amounts of energy from u2212 80 to u2212 70 within this band the cost function fc2 decreases linearly and runs from u2212 80 10 to u2212 70 5 by applying the exemplary embodiment in accordance with fig2 the prosumer p2 has so far been assigned an amount of energy of e 3 u2212.