Cloud　auditing　allows　users　to　leverage　digital　signature　evidences　to　undertake　remote　data　verification　and　consequently　determine　the　integrity　of　their　data　stored　in　the　cloud.　While　there　are　many　cloud　auditing　schemes　proposed　for　cloud　services,　deployments　on　large　scale　smart　grid　(SG)　are　known　to　be　challenging　in　practice,　for　example　in　terms　of　inefficiency　and　lack　of　robustness.　In　this　article,　we　propose　an　efficient　and　robust　cloud　auditing　scheme　for　SG　(hereafter　referred　to　as　SG-Audit).　Specifically,　we　utilize　mobile　edge　computing　(served　as　proxy　signer)　to　offload　the　signature　computation　loads　incurred　by　smart　meters　(SMs),　as　well　as　devising　an　efficient　proxy　signer　recommendation　strategy　to　ensure　each　SM　obtains　high　quality　service,　a　scalable　index　structure　to　reduce　the　signature　evidence　access　time　during　data　verification,　and　a　deduplication　and　sampling　based　challenge　data　index　generation　strategy　to　narrow　down　the　verification　scope.　Moreover,　we　also　define　three　strategic　threat　scenarios　supported　by　SG-Audit,　and　further　devise　a　secure　cloud　auditing　protocol　to　improve　robustness.　Through　rigorous　mathematical　analysis　and　extensive　experiments,　we　demonstrate　that　SG-Audit　achieves　increased　auditing　efficiency　(by　about　42%　on　average)　in　comparison　to　prior　work.　©　2004-2012　IEEE.