There is a general consensus that prevailing Energy Crises 2050 will lead towards a serious shortage of fossil fuels in near future. Avoiding Global warming and energy crises are two major challenges to be faced in the next decade. In this scenario, synthetic refrigerants are well known to create global warming and ozone depletion phenomena. Among natural refrigerants, CO2 having favorable properties in terms of heat transfer and thermodynamics, has been chosen as refrigerants in this study. This paper presents an optimal design and implementation of CO2 based solar water heater using evacuated glass tubes for low insulation area like Gilgit-Baltistan. The performance of designed/fabricated system has been measured using Thermosyphon arrangements. Several parameters, i.e. header design, filling pressure and temperature, height of tank, heat exchanger design, pipe size and its material, of this self-sustained energy free system have been thoroughly studied. Further, they have been optimized for best performance.