The Hall County Board of Commissioners will meet tonight to decide whether to enter into contracts with Siemens and Pepco Energy Services for proposed energy-efficiency projects over a 15-year window. But changing estimates have raised concerns about whether the proposed cost savings can offset the project expenses. Siemens and Pepco reviewed energy performance at several government buildings and public safety facilities, as well as plans to capture natural gas from local landfills for use in county vehicles.