The Reliability of power electronic devices has been an important issue since the early power electronic applications introduced. The power electronic converter plays a crucial role in the failures of a PV system. The unscheduled maintenance failure due to power electronics devices are 37 % of the total failure. In that 31% of the failures are due to the power semi conductor devices. In recent years, many researchers have conducted reliability assessments of power electronic devices, yet the reliability of numerous circuits used widely has not been evaluated. This project presents a comprehensive reliability evaluation of fundamental photo voltaic inverter. The reliability of the inverter is analyzed by calculating the mean time to failure for an IGBT module. The calculation was performed by Parts stress method to achieve better results. In the Parts count method, due to the direct relationship between component failure and temperature; we used PLECS to determine power losses in switches taking into account and the Junction temperature factor.