The mansion of the Nobel family is one of the most featured world recognized monuments of the city of Saint-Petersburg. The article deals with a reconstruction option of the Nobel’s mansion space aimed at gaining extra area to be used for the purpose of solar power generation. Photovoltaic systems are suggested to be used as an alternative energy resource to ensure in-house demand for heating. Inputs of solar radiation on the surfaces oriented in different directions have been estimated herein. A computation method and estimations for energy production of PV-modules placed under conditions of partial shading cased by the building’s wings have been presented herein as well. An optimal inclination angle of the modules with respect to the horizon, which can ensure maximum energy gains under weather conditions of Saint-Petersburg, has amounted to 35°.