Power tool

A chain saw (100) as a power tool which has an engine (111) and an electric motor (141) is provided. The chain saw (100) comprises a driving shaft (131) which is adapted to drive a saw chain (105), a controller (139) which controls the electric motor (141), and a driving source which provides current to the electric motor (141). Further, the chain saw (100) is adapted as the saw chain (105) is drivable in a hybrid driving mode in which the engine (111) and the electric motor (141) drive the driving shaft (131) simultaneously. The power source of the chain saw (100) includes a capacitor (138). The capacitor (138) is electrically connected to the controller (139).