Power system operators around the world strive to maintain the balance between energy supply and load demand. This is a complex and costly exercise with supply and demand varying every second and the need to ensure the balance to be within tolerable limits in order to maintain a stable grid. The addition of stochastic renewable energy, and already existing varying load, on power system network can experience stability challenges. This chapter investigates the impact of increased renewable energy generation, and power system behavior during frequency deviation and load mismatch. The results show a 400% increase in clearing time when the largest synchronous generator is replaced with renewable energy and a frequency perturbation of 0.2 rad/s is introduced. The system also resulted in 300% increase in clearing time with a 42% decrease in load demand if renewable energy has been added. Comparing a decrease in load to an increase in load of the same magnitude, it can be noted that there is approximately 60% decrease in maximum frequency deviation compared to load increase of the same magnitude. There is therefore a need to incorporate dynamic models of energy storage devices that will be used in implementation of control schemes for enhancement of frequency stability.