As the renewable energy industry grows and becomes a larger part of our energy mix, the concept of energy storage has made its way into the spotlight and has created some important pressing questions: Do renewables' inherent intermittency require some kind of energy storage, and should it be at the endpoint of use or closer to the utility (or both)? Do we even need an "energy storage" application, or can grid flexibility and responsiveness assume this role? If energy storage is indeed embraced, how should we weigh the options?