Should you leave your smartphone charger plugged in all the time?

Most of us do it, but how much money are we wasting by leaving our smartphone chargers -- not to mention all the other chargers we have and use these days -- plugged in 24/7? How much power are they wasting? Are they safe?
Written by Adrian Kingsley-Hughes, Senior Contributing Editor

In my view right now I can see almost a dozen smartphone, tablet, and laptop chargers. Oh, and I can see another powering my Amazon Echo. And another charging up a pair of earbuds.

So yes, quite a few.

They're all plugged in, and most of them don't have devices attached to them.

This begs a few questions. How much power are they using? Should I unplug them? Are they safe?

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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. While the WattsUp? PRO is a dedicated test meter, you can pick up domestic power meters from most online and brick-and-mortar electrical retailers these days.

Note: 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 September 2018, the average cost for 1KW h of electricity in the US hovered around $0.13. The most expensive residential power in the US is found in Hawaii, where it costs $0.32 per 1KW h.

Note: A reader got in touch to let me know that the listing I used there is somewhat incomplete and that the power costs in the US Virgin Islands is $0.39 per kW h.

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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 in the region of 130W of power a month, which equates to 1.5KW h a year, and that's adding some $0.20 on my power bill. Even at Hawaiian prices, that's only $0.47.

That doesn't seem like a lot, does it? And to be honest, given those numbers, it just isn't worth unplugging chargers with the idea to save money. I mean, if you had five chargers running 24/7/365, they'll cost you about a buck a year on average, or about $2.50 at big-bucks Hawaiian prices.

However, here are some things worth bearing in mind:

  • How many chargers do you have plugged in? One? Five? A dozen? It all adds up.
  • Also remember that different chargers can pull different amounts of power. The bigger the charger, the more it is likely to draw.
  • Non-genuine chargers can draw a lot more power (up to 10 to 20 times more, based on my testing). On top of that, the cheapest and nastiest ones aren't the sort of thing I'd be comfortable leaving plugged in all-day, every day.
  • Chargers can get hot, and if they are buried under clothing or books (or pets seeking warmth... cats especially are drawn to warm chargers) they can get even hotter, and this is something that you want to avoid.

Also, give a thought to the environmental cost of these continuously-running chargers. Millions of chargers left plugged in 24/7/365 translates into millions of kilowatt hours consumed every year. And each kilowatt hour of power produced equals about a pound of CO2 being released into the atmosphere.

With that in mind, maybe we should all unplug our chargers when they're not in use.

Alternatively, you can buy smart outlets that you can control remotely. You are replacing one active device with another, and in my experience these too can pull quite a bit of power when plugged in, but if you use them wisely you could use a single smart outlet to turn on and off a number of different devices.

Or perhaps a single outlet could turn off most of your devices in your office at the end of the day, or the chargers you have in your living room when it's time to go to bed.

From a safety point of view, I always recommend buying high quality branded equipment. Cheap, no-name stuff can, in my experience, be pretty awful. I have seen bad things happen. Fortunately for me, I was prepared for those bad things to happen, but I wouldn't have liked them to have happened while I was asleep, or when Mr Kitty was warming himself on the device.



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