A range extender for a vehicle, comprises an electric machine; an engine; and a controller, wherein the controller is configured to control fuelling of the engine, and is configured to control the electric machine to charge a battery of the vehicle using power from the engine and at other times to control the electric machine to drive the engine using power from the battery, wherein the controller is configured to increase the engine speed by controlling the electric machine to drive the engine using power from the battery whilst substantially not fuelling the engine.