How much electricity do all your smartphone chargers waste when not in use?

In my view right now I can see a number smartphone chargers. They're all plugged in, and there are no devices attached to them. Some have little LEDs on them, so they are clearly on, munching on power. Power that costs money, and the generation of which harms the planet we all share.

But how much power are they using, and 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. While mine is a dedicated test meter, you can pick up domestic power meters from most online and brick-and-mortar electrical retailers these days.

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 November 2019, 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 almost $0.31, and the cheapest is Louisiana at $0.0947.

I then took a genuine Apple iPhone (a 5W charger that comes with with the iPhone 11) charger and let it sip 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?

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According to my tests, a genuine Apple iPhone charger uses in the region of 135W of power a month, which equates to just over 1.5KW h a year, which means that if I lived in Hawaii, that charger would cost me $0.46 a year it I left it plugged in doing nothing. If I decided this was too much and moved to Louisiana, I'd save a quarter.

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 ten chargers running 24/7/365, they'll costs you about $1.95 a year on average, or about $4.60 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? They all adds up.
• 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 chargers aren't the sort of things I'd be comfortable leaving plugged in all-day, every day.

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

With that in mind, maybe we should all unplug our chargers when they're not in use. And having experimented with all sort of ways to do this, I've come to the conclusion that the easiest way is to use extension cords with switches for each outlet and switch them off and on manually, or for Apple or Alexa users (or those handy with IFTTT), smart sockets are an option.

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