In determining new power rates, regulators and Mississippi Power disagree over how much customers should pay. Monday, Atlanta-based Southern Co. said it wanted customers to pay $277 million more in assets than the Public Utilities Staff believes is justified. Although the difference would initially have little impact on rates, Public Utilities Staff Executive Director Virden Jones said Tuesday that customers would pay substantially more over time under the proposed plan. In June, the Public Services Commission said that the Kemper County Power Plant should run on natural gas rather than gasified lignite coal, and that power rates should remain steady of fall. The commission said it would set a status hearing to decide how to move forward if staff and the company can’t reach an agreement.