Pacific Gas & Electric (PG&E), a large US electric utility, wanted to demonstrate to the Federal Energy Regulatory Commission (FERC) that sellers in the California electricity markets during the summer of 2000 committed California ISO tariff violations. PG&E also wanted to calculate a set of competitive prices that would have been expected to occur in the California electricity markets if sellers had not committed tariff violations and compare those prices to the amounts actually received by sellers. Finally, PG&E wanted to calculate refunds that would be paid by sellers to California utilities for certain types of energy transactions in order to mitigate prices charged above just and reasonable levels.