Sunday, November 13, 2011

Does leaving chargers plugged in really waste electricty?

I have often heard people say that you can save significant amounts of electricity by unplugging your phone and laptop chargers when they are not in active use. However, I have also heard people say that this is rubbish because modern well designed chargers will consume virtually no electricity when not actively charging a device. I was not sure which advice to trust and so I decided to run some tests with my new current cost meter in order to check it out.

In order to test out how much electricity is used charging my phone, I made sure to make heavy use of it today and I completely drained its battery (not an unusual thing for me to do). Then I plugged it in to my phone charger and observed the electricity usage using my Current Cost monitor. Despite the fact that my charger was plugged in all day, it consumed no measurable amount of electricity until I plugged in my phone. As soon as I plugged in my phone the consumption jumped up to 4 watts for 2 hours before the phone was fully charged and the usage went down to zero again.

Based upon this measurement, I calculated that if I was paying 14 cent per KiloWattHour, I would spend roughly 50 cent on electricity to charge my phone for a whole year. Leaving the phone charger plugged in while not in use would make absolutely no difference to my bill.


  1. I've heard both sides of this as well. Your test is convincing enough for me. Nice work.


  2. Before you decide to leave your charger plugged in all day, you might want to read my later post where I compare different phone chargers. It seems that there are significant differences between different models.