This study analyses the performance of a solar panel system consisting of two subsystem, subsystem A consists of four identical units of solar panels arranged in series parallel and two identical units of batteries arranged in series parallel. The subsystem works if at least one solar panel and one battery work. Subsystem B consists of two identical units of battery and two identical units of inverter connected in series parallel. The subsystem works if at least one unit of inverter and one unit of battery work. When any of the units fails, it is immediately required to be repaired. Failure and repair rates are assumed to be exponentially distributed. The subsystems steady state availability, a key reliability metric, were derived and quantitatively evaluated through the application of the Kolmogorov forward equations method. The results demonstrate that system availability is significantly improve by adopting major repair. The finding provides a theoretical basis for predicting system performance and informing maintenance strategies.