DGs (distributed generations) or DERs (distributed energy resources) are becoming more and more widespread. Connecting to the grid as a new load customer or a new generation customer needs engineering evaluation via comprehensive system studies. Cost of interconnection depends on system topology for the area of interest, impact of proposed load or generation under normal and contingent system operating conditions, and the jurisdictional wire owner's technical requirements. Retaining a power system expert on the customer side to deal with local utility companies is analogous to with hiring a lawyer; it helps progress the project in more professional way. For example, technical negotiation through power system study could ensure interconnection cost is imposed fairly, reasonably, and without unnecessary cost or overbuild. We conduct power system interconnection study, regulatory interpretation, permit and license application, viability study, and economic analysis and forecast.