Zinc oxide (ZnO) nanowires were synthesised through two different methods; the vapour liquid solid (VLS) method and an aqueous solution method. Each method had its own set of parameters and changes in those parameters influenced the output voltage of a nanogenerator. Changes in output voltage occurred as a result of variations in the resistance and the carrier concentration of grown nanowires as the piezoelectric charges were screened or trapped. An optimal value for both the resistance and the carrier concentration was determined in order to optimise the output voltage.