After months of inquiry and weeks of controversial debate, the Hall County Board of Commissioners on Thursday voted down two proposed energy-efficiency contracts with Siemens and Pepco Energy Services. In the run-up to the vote, shifting financial estimates and skepticism about purported savings began to turn the tide against the projects, which called for lighting and water efficiency upgrades at county buildings, as well as converting sheriff’s office patrol cars and other county vehicles from diesel and gasoline to compressed natural gas. The Siemens contract, which initially called for $6.6 million in costs with an estimated $9 million in savings over 15 years, appeared to have the best chance of receiving the board’s approval.