Mobile devices periodically send resource usage reports to an energy server. The reports include information such as an amount of energy used during a time interval, and identify processes that are executed on the mobile devices during the time interval. These reports are analyzed by the energy server and are used to generate statistics regarding the energy used by the mobile devices and the processes that are executed by the mobile devices. When a mobile device experiences a suspected energy spike, the mobile device generates and sends a report to the energy server. After confirming the energy spike, the energy server uses the statistics and the received report to identify one or more causes of the energy spike. The causes can include one or more processes, or the mobile device itself. The mobile device can reduce the amount of energy used based on the identified causes.