The photovoltaic installation is to operate efficiently for about 25-30 years. Will it? It depends largely on the quality of the elements used, the design, but also on the installation itself. Wrongly installed modules, wrongly selected devices or careless connection of photovoltaic system components can not only reduce the efficiency, but even cause damage to the system. It is also a necessity to service the installation frequently. Common mistakes made by installers include choosing the wrong system, underestimating the inverter’s power, lack of protection, wrong installation angle of PV modules. As an installer, you must also make sure that the devices have the appropriate approvals and quality marks. Remember your health! Inappropriate preparation – lack of knowledge of health and safety rules – can lead to accidents at work!