The application of self-sufficient off-grid electricity system using both renewable energy and storage technology can be of use in the remote isolated area. Presently, cost effective analysis dedicated for the off-grid electricity system has been conducted from the power reliability perspective. Notwithstanding the fact that reliability is comprised both of adequacy and security, the existing approaches for the analysis of power reliability are particularly associated with adequacy rather than security. The main challenge of power security in the off-grid electricity system is in ensuring the undisturbed and reliable electricity supply even after the sudden disturbances. As such, the methodology of determining the appropriate capacity size of both the renewable energy and storage technology dedicated for the off-grid electricity system taking into account the impact of sudden system failure is firstly established. Subsequently, the determination of appropriate installation from cost and power security perspective is analyzed. The developed cost-security index is explored by varying the weighting factor. Finally, the sensitivity testing is conducted to analyze the impact of uncertainties arising from the determination of weighting factor. The developed algorithm from both cost and power security perspective would hopefully help the operator to evaluate the different strategies of off-grid electricity system. (C) 2017 Elsevier Ltd. All rights reserved.