In many regions, the term load serving entity (LSE) is used to refer to any electric market participant that provides supply to end-use customers. This may be a utility distribution company (UDC) or it may be a retail marketer. And in some areas this may be an aggregator. Other terms used include energy services provider (ESP), retail electric company (REC), or retail energy provider (REP). LSEs interact with Independent System Operators (ISOs) in organized wholesale markets as the entity that schedules and buys energy on behalf of the end-use customers that the LDC serves. In some ISO markets, UDCs also have capacity obligations. And in some U.S. states, UDCs may have obligations to ensure sufficient supply to maintain reliability.