An experimental study was performed to determine the thermal efficiency of thermosyphon heat pipe (THP) evacuated tube solar collector using silver-water nanofluid for commercial applications. Firstly, the synthesis of silver-water nanofluid was carried out which can maintain its long-term stability. The identification of nanofluid was determined by X-ray diffraction, scanning electron microscopy, UV - visible spectroscopy and thermophysical analysis. Secondly, the heat transfer properties of cylindrical copper THPs charged with silver-water nanofluid and pure water was investigated experimentally. Experiments of THP charged with silver-water nanofluid were repeated four times at intervals of two weeks in order to observe changes in the performance of THP. It was observed that the THP charged with silver water nanofluid maintained its improved heat transfer characteristic in the THP experiments. Nanofluid working fluid increased the efficiency of solar collector between 20.7% and 40% compared with the pure water. In conclusion, the experimental results show the use of silver-water nanofluid provides a significant improvement in the THP evacuated tube solar collector. (C) 2018 Elsevier Ltd. All rights reserved.