Energy storage system is an integral part of renewable energy utilization process. Different articles, reports and examples shows the importance of storage but to make a sustainable system that generates electricity from renewable energy a feasibility study on generated energy cost is require. The unit price of grid electricity includes all types of expenditure from generation to consumption also add some profit on it but never consider compensation value due to the environmental hazardous greenhouse gas emission, however renewable energy doesn’t emit any greenhouse gas. This paper presents the importance of storage in renewable energy environmentby extensive study and literature review; more oversimulation work has been carried out to validate the requirement of such storage system. The importance ofstorage and it’s feasibility were tested using HOMER, a computer aided tool developed by National Renewable Energy Laboratory (NREL). Solar and wind data of Rockhampton in Australia has been considered for this model. Net present cost (NPC), cost of energy (COE) and renewable fraction (RF) have been measured as performance metrics. Amount of emitted greenhouse gas from this mixed system has also been considered. The model has been refined with sensitivity analysis and it is found that storage makes the renewable energy (wind and solar) feasible to implement in terms of economy and environment.