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This is something I always wondered about: when I leave my charger plugged on the wall socket but not charging anything, is it still consuming energy?

Some notebook chargers have a led that is always on, so I guess it's consuming at least a bit. But what about Apple chargers? I want to leave my iPhone and iPad chargers always plugged under my desk (so I can just connect my device when I want to charge) but I'm worried they shouldn't be plugged all the time.

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6 Answers 6

up vote 4 down vote accepted

I measured my MacBook Pro’s charger, and the iPhone/iPad chargers, with a Kill-a-Watt-like device, and it didn’t seem to use any significant power when plugged into the wall on its own (e.g. it was less than 1 watt).

BUT:

  • I’m not sure if my device is sensitive enough to measure very small amounts of power though.

  • your mileage may vary. If you’re interested in this sort of thing, I’d get a little dongle of your own and do some measuring. Mine cost about £5.

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It does consume energy. Feel it, it will feel warm or even hot. It doesn't use much, but it is still a good idea to not waste this. Unplug it, or buy a power strip and turn off the power strip when it isn't needed.

To find out exactly how much, you could use a Kill-a-Watt, or read the MacBook Environmental Report (PDF). The current version (MacBook, May 2010, White) says the no-load power draw is 0.010 W. The older version (MacBook, 2008, Metal body) draws 0.15 W at no load. This is quite a difference.

0.15 W means if you left it plugged in for a year you would use 1.314 Kwh. Given a price of roughly $0.20/Kwh this would cost you about 25 cents per year. If the computer is on the whole time (at 14 Kwh) the cost would be about $25/year.

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I wouldn't recommend doing this. Also, never keep your devices plugged in constantly... This will reduce its battery life. It's a good idea to do a power cycle every month to keep a healthy battery (let the battery go down until it dies, then recharge fully).

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It will consume energy even when not connected to your Mac. Also, the longer you leave them plugged in, the more likely they will be damaged by an electrical surge or lightening strike etc. Best thing to do is probably have a multi-socket lead which your chargers plug into under your desk and you can just pull that out of the wall when not in use. That protects your equipment from electrical issues and saves your back from getting under the desk!

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As others said - it does consumes energy though less than 1 watt hour and it is designed to being plugged 24/7.

So it is ok to leave it on, but I wouldn't. We should always have at least a power strip for electronics and use its switch regularly anyway.

But the real point is: do you have extra U$79 to spend and have handy an extra charger? If so, then just leave it on for convenience (and lazyness)!

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All your chargers are designed to support being plugged in 24 hours a day. Don't worry about them wearing out. If you are concerned about a small charge to your electric bill or if you're trying to do your part to waste less electricity, then you can plug them all into a power strip. When you aren't using them, turn off the power strip.

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