Energy storage is needed to help the power grid of the future in balancing the highs and lows caused by intermittent renewables such as solar and wind. Flexible demand ? such as air conditioning ? can provide the same service as batteries by manipulating their demand around a nominal baseline so that the increase and decrease of demand appears like charging and discharging of a battery. The advantage of these ?virtual batteries? over real batteries is their low cost, since only a change in software is needed. A challenge in the effective use of both real and virtual batteries is coordination: a large number of them need to be coordinated so that together they supply what the grid needs. At the same time, the Quality of Service (QoS) of each consumer ? on whose premises a flexible load or a battery resides - must be maintained within strict, pre-negotiated, bounds. In this webinar, we will describe methods for coordinating a large number of energy storage and flexible demand resources, and discuss the pros and cons of these methods.