A system for conducting a computer-based, simultaneous, multiple round, descending clock auction for basic generation services includes a web server for receiving bid data for one or more users for basic generation service products, an application server host application software, which processes the one or more bids according to at least one auction rule, tracks the auction, monitors the auction, and/or determines when to end the auction, and a database server, which stores auction data. A method of conducting a computer-based, simultaneous, multiple round, descending clock auction for basic generation services includes the repeating steps of receiving bids indicating desired tranche units of basic generation service products, calculating next round prices for each product, and sending round results to bidders. The subsequent round price for each of the products and a notice of the number of tranches bid during the immediately previous round of bidding for each of the products and/or the amount of excess supply offered. When the number of tranches bid for the round of bidding are equal to or less than the certain threshold for each of the products such that no further bidding can take place under the auction rules, the auction ends after the round of bidding and awarding winning bidders an ending price for each of the at least one of the plurality of products won by the winning bidders.