This master thesis is intended to investigate the profitability of transparent solar windows which concentrates parts of the invisible light to a solar cell.This makes it possible to generate electric energy while the window still is transparent. Other gains apply such as the removal of solar radiation into the building which makes it possible to decrease the amount of energy needed for cooling. The study will investigate profitability of transparent solar windows by simulating energy used for heating and cooling and by investigating profitability of the produced energy. The results show that it is not economically justified to use transparent solar windows for electricity generation with present techniques and with Swedish climate. It is however economically justified to use as a isolating window in buildings. The master thesis has been completed at Skanska in Stockholm.