EMERY P. DALESIORALEIGH, N.C. (AP) â¿¿ Pressure could increase on North Carolina utilities regulators to justify decisions to charge customers hundreds of millions of dollars more as part of a case the Supreme Court heard Tuesday. State Attorney General Roy Cooper's office argued that there's little evidence the North Carolina Utilities Commission independently analyzed the consumer impact of allowing Duke Energy to raise electricity rates for its 1.8 million customers by 7.2 percent. The commission is responsible for balancing the interests of both customers and investors in what are regional monopolies, while ensuring the companies are healthy enough to maintain a system of constant electricity supply. The Supreme Court can reverse the commission's January decision to allow the rate increase, which generates an extra $309 million a year for the country's largest electricity company. The increase included a 10.5 percent profit for Duke Energy's subsidiary operating in most of the state from Durham west, but pushed typical residential bills up by $84 a year to almost $1,236. "Consumer interest is supposed to be on a level playing field with shareholder interests," Cooper's consumer protection division head Kevin Anderson told the court's seven justices. "Yet we had expert testimony here that only focused on the impact to the utility's credit rating and shareholder interest." While hundreds of consumers last year objected that Duke Energy's requested increase would pile misery atop high unemployment and home foreclosures, the utilities commission's order approving the lower rate increase doesn't specify what weight it gave those warnings, Anderson said. There is "this notion put forward that when it comes to consumer interests the commission's findings and conclusions don't have to be specific. They can sort of be vague," Anderson said. Justices should question "did the commission do what it said it did, and if so is there any evidence as to how it factored that in?"