According to Bijlibachao.com, a cell phone charger can use anywhere from 3 to 7 watts for an average charging session. The main reason for the variation is that it takes different lengths of time to charge different cell phones.
A few tips can help cell phone users conserve energy when charging phones. First, once the phone is fully charged, switch it off at the plug source because a transformer continues to use electricity if it is not switched off. Second, avoid non-branded chargers because the original charger provided with the phone is specifically designed to be economical for that model. Finally, ensure the charger does not overheat, as an overheated charger is working inefficiently.