The implementation of renewable energy sources and energy efficiency measures for administrative buildings, contribute for reduction of costs for electricity and other fuels. For estimating the optimal rooftop photovoltaic placement on administrative building, a placement analysis is needed. This analysis enables designer to define the optimal placement of the PV modules on the roof using Building Information Modelling (BIM). BIM is based on digital technologies developed with the special purpose for creating a digital model of a building that contains all its physical and functional characteristics and enables easier development of PV system integrated in building. The selected administrative building has a very irregular roof divided on 14 separated rooftops with different orientation and slope. To obtain efficient PV system, the rooftop photovoltaics placement analysis is realised in three different scenarios when all 14 different rooftops are covered by PV modules, 10 rooftops facing north or the ones between other rooftops where shading is imminent, are exempt and 5 rooftops have longer exposure to sun light, or more than 1000 hours per year. The PV system, designed on 5 selected rooftops contains 335 PV modules with a total power of 135 kW and estimated annual production of electricity of 144 074.26 kWh.