Distribution systems are designed for unidirectional power flow from the transmission system at the top to individual users at the bottom. If you start doing th

Distribution systems are designed for unidirectional power flow from the transmission system at the top to individual users at the bottom. If you start doing things like reversing power flow and exporting power through already very heavily loaded distribution transformers you create bottlenecks, stability issues, and safety issues that were not originally designed around. If you expect users to be importing and exporting power from their residence you need to have automated protection that can disengage those residences from the grid at a minimum, and probably a lot more that I am not an expert on. My day job is designing control systems for renewable generation and as a result I have some exposure to transmission level and generator bus level protection schemes and they can be quite complex!