Analytical expressions have been developed to calculate the temperature dependent electrical efficiency (eta(m)) and the effect of water flow on the performance of a-Si thin film photovoltaic (PV) modules. The calculated results have been validated by experimental investigations on commercially available a-Si thin film PV modules. With water flow on the PV module, eta(m) is observed to increase, which has been attributed to the dissipation of thermal energy associated with the PV modules due to water flow on it. The effects of mass flow rates of water (m(w)) on module to water heat transfer coefficient (h(m,w)) and eta(m) have also been calculated. Increment in m(w) increases both the h(m,w) and eta(m). For low m(w) of 0.001 kg/s, the h(m,w) and eta(m) were calculated to be 14.2 W/m(2) K and 7% respectively, whereas for high m(w) of 0.85 kg/s, the h(m,w) and eta(m) were calculated to be 413 W/m(2) K and 7.45% respectively. Daily average electrical efficiencies of a-Si PV module with and without water flow have been found to be 7.36% and 6.85% respectively. Overall thermal efficiency and overall exergy of PV module with water flow have been found to be 22% and 7.33% respectively. (C) 2014 Elsevier Ltd. All rights reserved.