With the quickly developing of grid-connected Photovoltaic (PV) systems, its reliability is being concentrated widely. The PV inverter is the weakest part of the PV system. Therefore, this paper presents an overview of the reliability of PV inverters in grid-connected applications. The discussion includes different PV inverter configurations for grid-connected systems, basic principles of reliability, and the importance of reliability evaluation in PV inverters. Finally, presents different lifetime estimation methods available to evaluate the reliability of the most frequent failure components in the PV inverter, which are power devices and dc-link capacitors. The main objective of this review is to provide the basics of reliability research in PV inverters.