Abstract Photovoltaic water pumping system (PVPS) is considered one of the most important and promising application of solar energy in remote and rural areas. The random nature of solar energy is one of the main obstacles that encounter the designer to design an effective PVPS. Thus, an optimal and effective sizing approach is essential to ensure satisfactory performance. In this paper, a technique for order performance by similarity to ideal solution (TOPSIS) method integrated with analytic hierarchy process (AHP) method is proposed to optimally size PVPS based on techno-economic aspects. The loss of load probability (LLP) and excess water volume are considered as technical criteria, whereas the life cycle cost (LCC) is represented as an economic criteria to size the system. The hybrid AHP-TOPSIS sorts the PVPS configurations from the best to worst based on predefined weights for each criteria. The optimal configuration is found 5 PV modules and 4 PV strings are connected in series and parallel, respectively with 79 m3 as a maximum capacity of storage tank. The performance of system is tested based on the proposed optimal configuration over a year using hourly meteorological data. The results show that the proposed system offers high reliability throughout the year with LLP, LCC, and deficit water volume around 0.0004, 10524.9 USD, and 4.4629 m3, respectively.