Disclosed are device implementations for a hybrid energy harvesting device and methods for harvesting mechanical energy from the ambient. The various device implementations utilize a combination of electrostatic energy conversion and piezoelectric energy conversion elements. The method simultaneously converts mechanical energy into electrical charge by electrostatic and piezoelectric energy harvesting. The devices include a piezoelectric harvester including a pair of electrodes and piezoelectric nanocomposite polymer, an electrostatic harvester including an electret film and a pair of electrostatic electrodes.