Behind-the-Meter Solar Photovoltaic in Connecticut: Effects on Network Load Profile, and Lessons for Renewable Integration A Case Study on the United Illuminating Service Territory

Promising to lower the demand for conventional generation, reduce network congestion, and contribute to a greener electric grid, rooftop solar has been the poster child of the renewable energy revolution. After over a decade of rooftop solar development in Connecticut, I investigated the effect of behind-the-meter solar on United Illuminating’s network, focusing on the change of load profiles manifested in peak load, peak hour, and max ramp rates. Intended as a “reality check” for the implications of behind-the-meter solar development on the network, my study revealed that current levels of rooftop solar penetration have proven beneficial: reducing peak network load by as much as 2% and max ramp rates by as much as 20% during non-winter months. However, benefits from behind-the-meter solar diminish as capacity continues to grow, thanks to the non-dispatchable nature of renewable resources like solar. The mismatch between network demand and solar supply ultimately results in overgeneration and increased max ramp-up rate with around 300MWDC of installed capacity. For better or for worse, a straightforward, one-size-fits-all solution for increasing hosting capacity for renewables likely does not exist. Instead, the grid will need to become more flexible and resilient, taking measures that go beyond battery storage.