The concept of distributed generation has received widespread attention in the power industry. Increasing proliferation of these distributed generators necessitates changes in how power distribution system are designed, operated, and maintained. Conventional US distribution systems are radial with an inherent assumption that the flow of power is always from substation to end user. Installation of distributed generation on these radial systems invalidates the assumption and introduces a range of issues like stability (for larger DGs), voltage regulation, fault current contribution, islanding, power quality, reverse power flow, harmonic injection etc. Energy Consulting performs engineering studies to assess and analyze the impact of distributed generations. We have extensive, global experience performing interconnection requirement studies (IRS) and impact studies for various distributed energy resources (DERs) including CHP, solar PV plants, wind generation, and battery storage.