Should you unplug your smartphone charger when it's not in use?

How many smartphone and tablet chargers do you have? Ever wonder how much it's costing you to leave them plugged in 24/7, or whether you should unplug them when they're not in use?

In my view right now I can see six smartphone and tablet chargers. They're all plugged in, and there are no devices attached to them. How much power are they using? Should I unplug them?

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Rather than guess, I decided to break out my test gear and do some testing. My test meter of choice for this test is the WattsUp? PRO power meter, as I can use this to measure how much power a device is drawing.

Power is priced in kilowatt hours (KW h, or 1,000W), which is 3.6 million joules of energy. A device rated at 1,000W running for one hour will use 1KW h, while a device rated at 100W will take 10 hours to consume 1KW h.

As for costs, according to data published by the US Energy Information Administration for January 2016, the average cost for 1KW h of electricity in the US was $0.12.

I then took a genuine Apple iPhone charger and let it draw power (with nothing attached to it) over the course of a few days.

No surprise here: a smartphone charger consumes power -- even when it's not charging a smartphone.

But how much power does it consume?

According to my tests, a genuine Apple iPhone charger uses about 130W of power a month, which equates to 1.5KW h a year, or $0.18 on my power bill.

That doesn't seem like a lot, does it? To be honest, it doesn't seem worth unplugging chargers when they're in use. I mean, five chargers costs you about a buck a year.

However, it's worth considering the following:

  • How many chargers do you have plugged in?
  • Non-genuine chargers can draw a lot more power (up to 10 times, based on my testing).

Also, give a thought to the environmental cost of these continuously-running chargers. Millions of chargers left plugged in 24/7 translates into millions of kilowatt hours consumed every year. And each kilowatt hour equals about a pound of CO2 being released into the atmosphere.

Maybe we should all unplug our chargers when they're not in use.

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