Within the scope of this study, the efficiency of Monocrystalline, polycrystalline, and thin film photovoltaic panels have been experimentally investigated in Karabük conditions. In the frame of the research, the efficiencies of the panels have been compared by using the amount of incoming radiation, current, voltage, and the amount of power generated by the panel. When the datasheets of panels are viewed, efficiency comparison has seen as monocrystalline, polycrystalline, and thin film, respectively. According to the experiments made, while the efficiency of monocrystalline panel at 250 Watt varies between 12-16%; the efficiency of polycrystalline panel increase nearly 21% based on the amount of radiation; whereas it has been seen that, the efficiency of thin film couldn't exceed nearly 5%. During the measurements, if the air temperature is considered between 30-35 oC, the efficiency of thin film estimated will be low. In Turkey conditions, when the unit price of these panels is considered, using polycrystalline panel for the investments seems much more attractive. As the efficiencies of thin film are low, it has been the last one in comparison. When it is considered that, the investors especially hesitate between polycrystalline and monocrystalline panels, experimental results give a reasonable answer.