This paper presents a topology comparison of a hybrid low-voltage step-up dc-dc converter in terms of European Efficiency. Such converters are suited to be integrated with solar cells, thus forming a photovoltaic energy harvesting architecture dedicated for an integrated realisation of a solar range extender for electric vehicles. Except of a discrete power stage realisation, the rest of a system, such as control, time and power management, shall be monolithically integrated in the AMS 0.35μm HV CMOS process. Developed efficiency model allows straightforward comparison of different converter topologies, as shown on an example of the dc-dc converter which supplies the electric vehicle auxiliary board net (12 V) with photovoltaic power up to 40 W from a stack of 9-10 solar cells. Optimisation of the design variables: the external power switches, and the converter switching frequency is outlined on a given example.