Monitoring system is essential to maintain optimal performance of photovoltaic systems. An automatic fault diagnosis technique in a monitoring system plays critical role in detecting causes affecting the energy production. This paper proposes a new fault detection technique that analyzes the anomalies observed in terminal characteristics of faulty PV strings and corresponding array. The terminal voltage difference between the module in healthy string and the healthy module in unhealthy string can be employed to locate faulty modules. The main advantage of proposed approach is that it voids the need of string current sensors, and reduces the number of voltage sensors using optimal location of voltage sensors. In this technique, power line communication technology based data transmission is used to monitor each PV module. Additionally, a user friendly web application is developed for easy access of monitored data via Internet. Moreover, an economic analysis has also been carried out to study the cost effectiveness of the proposed fault detection technique; considering different values of interest rate and energy tariffs. The profitability of installed grid connected photovoltaic system is determined through its parameters net present value and pay-back period. Experimental results are provided to demonstrate the effectiveness of proposed fault detection technique. (C) 2017 Elsevier Ltd. All rights reserved.