Small-scale electricity generation from renewable sources is developing fast in low voltage distribution systems. The consumers that use PV panels can benefit from regulations that allow reselling their generation surplus as prosumers, back to the grid or in local micro-markets. However, these advantages go hand in hand with changes in the operating conditions of the electrical networks that can lead to increased power losses and decrease in quality of supply. This paper investigates the possibilities of optimizing the prosumer surplus injections on the three phases of four-wire networks, with the aim of reducing the power losses. The performance of two multi-criterial optimization algorithms, MOPSO and MEPSO, are compared for this purpose. The results of a case study are presented.