High net load variability, driven by high penetrations of wind and solar generation, will create challenges for system operators in the future, as installed wind generation capacities increase to unprecedented levels globally. Maintaining system reliability, particularly at shorter time-scales, leads to increased levels of conventional plant starts and ramping, and higher levels of wind curtailment, with sub-hourly unit commitment and economic dispatch required to capture the increased cycling burden. The role of energy storage in reducing operating costs and enhancing system flexibility is explored, with key storage plant characteristics for balancing at this time-scale identified and discussed in relation to existing and emerging grid-scale storage technologies. Unit dispatches for the additional storage plant with varying characteristics highlight the unsuitability of energy only markets in incentivizing suitable levels of flexibility for future systems with high net load variability.