Energy Efficiency of Mobile Device Recharging

Jussi Ruutu, Nokia Research Center, Finland Jukka K. Nurminen, Aalto University, Finland *corresponding author Kari Rissanen, Helsinki Region Transport, Finland ABSTRACT Because of losses in electricity conversion and storage only part of the energy taken from the power grid produces useful work in a battery-operated mobile device; the rest evaporates as heat. We analyze the recharging activity of a mobile phone to understand the efficiency of the different units involved (charger, EPM chipset, battery). Our measurements show that the efficiency is quite low; only about 15 % of the electricity from the power grid ends up being used for the actual computing and communication elements of the mobile phone. It seems that there is room for improvement in the recharging efficiency. However, as the consumption of electricity of a single phone is small the incentive for improvements has been weak.