This paper discusses how micro-grids availability during natural disasters and in their aftermath can be assessed. The analysis focuses on two critical groups of components that allow micro-grids to improve power supply availability: distributed generators and local energy storage. For distributed generators and, due to their importance during natural disasters, this paper presents a novel focus by exploring the importance of lifelines for system availability. Renewable energy sources are identified as valuable distributed generation assets during disasters because they do not require lifelines; yet, their variable generation nature leads to the need for significant local energy storage. Additional local energy storage may be desirable as a backup solution to address potential failures that would blackout the load because they reduce the impact of lifeline performance during disasters on micro-grid availability. Analysis of micro-grids availability is performed based on Markov state space models and calculated using minimal cut sets approximations. This calculation method has the advantage of being very simple, not requiring extensive knowledge in the subject or computational needs. Results are verified with numerical experiments using Monte Carlo simulations.