The U.S. power grid is undergoing a transformative shift as renewable energy growth accelerates across all ISOs. Regions that historically had minimal renewable penetration are now experiencing a surge in solar and wind development, while areas once dominated by a single renewable resource are diversifying their energy mix. This ongoing expansion is reshaping grid dynamics, influencing market behaviors, and driving changes in price patterns. As the energy transition progresses, understanding these evolving trends is critical for anticipating future grid performance and market impacts. However, as more of a single resource (solar or wind) enters a market, it drives down prices during sunny or windy periods, ultimately reducing the overall value of that resource. This price-dampening effect intensifies as market share increases—but by how much, and how quickly?

Figure 1 | Renewable Market Share Over Time for US ISOs

This is a complex but crucial question, given both the ambitious long-term renewable energy targets across the U.S. and the rapid short-term buildout of certain resources in specific regions (notably solar in ERCOT). To shed light on this issue, we analyzed capture ratio and renewable market share data across PJM, MISO, ERCOT, SPP, and CAISO—the ISOs where total renewable generation (combined between solar and wind) has surpassed 5% market share.