Controlling the thermal losses in the semiconductors ~s well. as the Co~mon Mode Voltage (CMV), are important Issues In the design of power electronics converters for photovoltaic applications. At present time there are several topologies that offer a good performance regarding losses and CMV. In this paper an evaluation of three of these converters topologies: U5, UERIC and NPC transformerless for single phase PV systems will be carried out by means of sim ulations performed wi~h P.SIM 7.05. This s~ftware permits to estimate accurately the switching and conduction losses, thanks to its Thermal Module. This analysis together with the CMV study for each case will permit to establish the pros and cons of each topology.