Whether greenhouse gases are priced at the power plant level or the portfolio level?that is, at the utility?the cost of a greenhouse gas cap-and-trade program will look much the same to consumers, according to economists. ?The price effect is identical,? said Ben Hobbs, Johns Hopkins professor in the department of geography and environmental engineering, June 8 before the California Independent System Operator?s Market Surveillance Committee. If the price of carbon dioxide and other greenhouse gases is attached to the point of electricity generation, aka ?first seller,? then that price would be passed onto the utility that buys electricity for distribution. In turn, that premium would be passed onto consumers. This is also being discussed under the rubric, ?source-based cap.? The other point of attaching a price to greenhouse gases under consideration by the state is at the utility, or load-serving entity, level. This also would be passed onto consumers. It is being discussed under the name, ?load-based cap.? ?It?s a double-edged sword,? said Nancy Ryan, adviser to California Public Utilities Commission president Mike Peevey. The economic theory is to price energy so it is painful to consume and to reduce emissions over the long run. However, economists voiced concern that many consumers will be helpless to make investments or change their consumption habits. Some economists also worried that higher rates that include greenhouse gas prices could send the state?s economy into a tailspin. According to stakeholders at the June 8 workshop, Southern California Edison prefers a source-based cap. Pacific Gas & Electric also favors a first seller, or source-based, approach, believing it would result in more efficient use of power plants by capturing the environmental costs before they are dispatched.