In the U.S., roughly five billion megawatt-hours of electricity are sold at the wholesale level, i.e., sold to a utility or other entity reselling that energy to residential, business, or industrial customers. There is no single national market for these wholesale electricity sales. In some regions, these sales are conducted bilaterally, through direct contact and negotiation, through a voice broker, or through an electronic brokerage platform, such as the Intercontinental Exchange (ICE). In other regions, specifically in the Northeast, Mid-Atlantic, Midwest, California, and Texas, there are wholesale electricity markets operated by large entities known as regional transmission organizations (RTOs) and Independent System Operators (ISOs)—collectively referred to as “RTOs.” Bilateral transactions can also occur in RTO regions, but through separate settlements and in compliance with complex RTO rules. These RTO markets provide for the wholesale sale of electric energy (both day-ahead and real-time purchases), as well as ancillary services. Some RTOs also operate capacity markets.