Distributed generation (DG) is making a comeback. In the late 1970s, federal legislation sparked a flurry of interest in the topic. Today it is once again an industry buzzword. Standards development, equipment testing, and project demonstrations are flourishing. However, this renewed interest poses the following unresolved questions. What are the requirements for interconnection with electric distribution systems? How will significant amounts of DG actually impact real-world distribution systems? And how do we go about analyzing, designing, and operating DG systems that no one has seen?