Monday 6 October 2014

batteries - How much power does a cell phone charger actually use?


I was trying to figure out how much power I actually use when I am charging my phone. Here are the specifications of my charger:



  • Input: 100/240 V, 50–60 Hz, 0.15 A

  • Output: 5 V, 0.7 A


I've heard that in order to calculate this, you need to pay attention to the input.


$$P = V\cdot A = 240\ \mathrm V\cdot 0.15\ \mathrm A = 36\ \mathrm W$$


I charge my phone for 4 hours a day at most. In that case, I use 144 watt-hours a day, and 51840 Wh a year, or 51.84 kWh. And that seems awfully lot, considering that all the articles I've read about the power consumption of chargers stated that they used about 2 kWh a year. I know I charge my phone too much (I really need a new battery), but it still doesn't add up. Are my calculations wrong? And if they are, what is the correct number?





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