Petroleum (Hydrocarbon - HC) based fuels are used for powering automotive and local power generation systems. Hydrocarbons on combustion produce gases such as CO2, CO, HC and NOx which affect human health as well as environment. Introduction of Hydrogen in Internal Combustion (IC) engine reduces emission and increases the performance. HHO gas which is produced through electrolysis of water can be used instead of hydrocarbon based fuels as the gas contains both Hydrogen as well as oxygen. Due to the challenges in storing Hydrogen, HHO gas is produced onsite through electrolysis process. This article presents the investigation on producing HHO gas through electrolysis onsite. A numerical calculation was done using empirical formula to predict the production of HHO gas. The electrolyser's performance analysis showed that maximum of 0.75 LPM of HHO gas was produced at 80 degrees C and by supplying 40 A-h. The numerical calculation showed that at the similar working condition the HHO gas produced was 1.3 LPM. The trend of both experiments and model was same for varying the current and rate of generation of HHO gas. This article also presents the effect of parameters such as concentration of electrolyte solution on potential, effect of time and the effect of temperature on production rate. The energy required and the number of modules or units of HHO gas production for real time engine application has been analysed and reported. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.