A large and increasing element of certain wholesale electric markets is capacity markets. Capacity markets are a mandatory program that pays resources for being available to meet peak electricity demand. In the U.S., three independent system operators (ISO) and regional transmission organizations (RTO) use capacity markets: New England ISO (NE-ISO), New York ISO (NYISO), and PJM Interconnection. Of the three, PJM is the largest both by population and the size of its capacity market. PJM's territory covers all or parts of 13 states and the District of Columbia. PJM serves 65 million people and has 180 GW of generating capacity. PJM runs the largest capacity market in the U.S. The annual value of PJM's capacity markets for 2017 was $8.55 billion, and the cleared capacity for the 2021/2022 delivery year was 163,627.3 MW. However, in recent years, PJM's capacity market has come under greater scrutiny as the generation mix transitions to include larger amounts of renewable and storage.