text: very little, because the current from pizo is very small,\nie: in   nano Amps,   and since  W= I  *  V \nfor example:     0.0000001 * 1000 = 0.0001 watts which is very little .\nso power input is more than power out put,  \nunless u have lots of free vibration and lots of cheap pizo to make it viable