How much power does your smartphone charger waste?

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 to save a few dollars?

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?

See also: Why smartphone and laptop batteries explode, and what can you do to protect yourself

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 April 2017, the average cost for 1KW h of electricity in the US hovered around $0.12. The most expensive residential power in the US is found in Hawaii, where it costs $0.30.

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 $0.18 on my power bill. Even at Hawaiian prices, that's only $0.45.

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 costs 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.
  • 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.

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 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.

See also: