A number of market forces drive the growth of battery storage system market rapidly. On one hand, battery-related companies such as material providers, battery makers, electric vehicle vendors, PV system integrator and heavy industry players are expanding their business area and building cross-industry opportunities to de-risk their primary business and generating secondary value streams. The ever-increasing demand helps with further economy of scale for battery manufacturing and results in drastic price reduction. On the other hand, the large deployment of distributed generation in behind-the-meter (BTM) sector and increasing renewable generations such as wind and solar in the grid-connected sector are requiring energy storage to be fit as part of whole system. It is interesting to find it is the general trend that the PV compensation scheme like feed-in-tariff is reducing by various countries globally, which may have a big impact in the further PV deployment. However, at the same time, favorable policies are addressing the importance of energy storage, including financial loans, subsidies, and incentive programs. The interest in energy storage will stimulate further deployment of renewable energy. Those factors have provided the foundation for the hype brought by energy storage, especially electrochemical battery energy storage systems (BESS). With the launch of Teslas Powerwall on April 30, 2015, tremendous interests have been attracted and a large number of players as well as products are overwhelming the market. BESS, with the capabilities to provide high energy, high power and both, have become an important consideration in grid-connected applications such generation, transmission & distribution networks and ancillary services. Increasing pilot and trial projects are on-going.