According to last month's Regulatory Staff report, SCE&G applied nearly 22,000 weather-based adjustment factors to customers' bills between the program's launch in August 2010 and August 2013. Calculations are based on 19 different equations for different groups of customers, with each group having 20 separate billing cycles. So customers are billed differently even within the same category.The agreement is a good deal for consumers, but concerns of bills spiking during a cold snap will continue, said Frank Knapp, president of the Small Business Chamber of Commerce and another petitioner. That's why the agreement promotes the budget billing option, he said. "Especially this winter, I think we're going to have really cold weather and really high bills," Arnold said. "People have to be able to budget for variable bills. Budget billing is the way to do it." The utility said customers overall have paid $25 million less over the last three years than what they would have without the adjustments. The state has not verified that number, and since the utility's not looking to recoup it from customers, there's no longer a need to attempt to do so, Scott said. The estimated savings to customers include a remaining $8.7 million balance resulting from what SCE&G calls an over-credit in the weather-based adjustments over several months in 2011.The billing error initially totaled nearly $14 million. But it has recovered some through subsequent adjustments, Boomhower said. It seeks to offset the rest through its interest rate swap contracts, which locked in low interest rates for future debt. The utility will not gain it by raising rates, it pledges in the petition.