In recent years, electric vehicles (EVs) have been widely accepted by general publics due to their low emissions. Particularly, those EVs which are able to be connected to power grid have earned lots of attention. In this paper, a multilayer framework is newly proposed for vehicle-to-grid operation. In this framework those gridable EVs can serve as resources to provide their capacity and energy service or as loads to be charged directly. The corresponding aggregator works as a smart controller for the framework, which is responsible for forming aggregations of gridable EVs and determining which vehicle to be a resource or a load. Cost-emission analysis is carried out based on this framework. Hence, operation cost and emissions can be reduced by using these gridable EVs.