Solar flat plate collectors nowadays find more applications considering the cost involved with conventional water heating systems using fossil fuels. The performance of these systems can usually be enhanced by varying select important parameters of the system for improved heat transfer ability of the collector. Therefore, this work is aimed at evaluating the effects of nano-Nickel Oxide (NiO) coatings on liquid flat plate collector for better heat transfer effect. Two flat plate collectors are designed and fabricated with same operating parameters such as collector area, system size and spacing, pipe diameter and size of collecting tank, etc. The heat transfer effect is simultaneously studied in these two units to observe the effect of nano coating in comparison with black chrome coating