Book excerpt: "The transformation of the electric grid from the traditional central station model to a more dynamic and interconnected system of distributed generation and distribution is a huge change in our lives, and yet one that is barely noticeable in day-to-day life unless you actually are looking for it. If you are looking, though, the rate of change is breathtaking. I know this first hand because in the roughly three years we have been working on this book the landscape already has evolved dramatically. In this time, topics we thought were interesting, such as battery storage, became drivers to the discussion while other topics faded in relevance. Indeed, one of the challenges of writing this book is our effort to assemble information that would remain interesting and useful to readers even as the technology and the law advanced. With the help of all of the authors and other contributors to this project, I think we have achieved this"--