Operating system supporting cost aware applications

A mobile computing device that supports cost-aware application components for operation over a metered network. A current basis for computing usage charges over one or more networks may be made available to the cost-aware application components through an application programming interface supported by an operating system service. That service may receive a policy for charging for data usage over a network and may also obtain information defining data usage for the mobile computing device. Based on this information, the service may determine a current basis for charging for data usage. With this information, the application component can determine a manner for executing network operations that involve data transmission over the network, such as deferring the operation or selecting an alternative network.