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My co-workers (who worked with the company longer than I have) loves to remove their laptop's power cord when they need to move around the office.

I frown on this practice since they usually don't remove the power brick from the power socket. I've told them numerous times that its dangerous to leave the brick unattached to the laptop and that they should remove it from the socket if they need to move around.

I think I need a better argument on why they should stop this practice. Does anyone has any experience to share to discourage this behavior? Is there a research or article somewhere that shows how much power is wasted?

Edit: If you think I'm wrong and leaving the power brick connected is not dangerous, go ahead and prove me wrong. :)

MrValdez
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11 Answers11

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Can I flip this around and ask why you think it is dangerous?

Is it the danger of it bursting into flames? (Miniscule) Is it the heat given off by the brick perhaps melting nearby items? (Maybe - chocolate?) Is it the trip hazard from the cables? (On a desk?) Is it the untidiness? (People are messy...) Is it the energy waste? (~1W from this Coding Horror post)

None of those strike me as 'dangerous'. Sorry.

fourstar71
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The amount of power consumed by the adapter when the laptop is not drawing any load is minimal. There's the parasitic power losses involved in having the voltage converter produce its output voltage, but without the laptop there's no real current being drawn from the wall.

The only things drawing power when the laptop is not plugged in are the resistive elements and diodes in the adapter itself. What about leaving the adapters plugged in do you think is dangerous?

ParoXoN
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as long as the power supply gets warm/hot despite unused, you've got a brilliant argument for energy saving.

lImbus
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A laptop power supply has to convert 110V AC to (say) 12V DC. It does this usually with a switching power supply. A switching power supply is quite efficient (around 90%), so it only takes say 110 watts to produce 100 watts of output.

Under no load (disconnected) they consume a small amount of power to operate the electronics. A power supply should not be hot under no load. The only hazard is if you apply a short circuit across the terminal (the business end that goes in the laptop), you can destroy the power supply. Good quality switchers have output protection which will sense the short circuit and shutdown the output while the short condition is in effect.

Yes, you can also trip over the cord.

digitxp
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TJ Golfs
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I must admit, that very often I do it. If I'm going to unplug laptop for short time, I don't unplug the PSU. AFAIK, when not used, it doesn't consume any electricity. It gets hot, because power conversion is never 100% efficient. So some 20-30% of electricity drawn gets converted to heat. But when laptop is unplugged, 20-30% of zero is zero.

The risks I see is cable lying on the floor or in the case of power surge.

vartec
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Hypotheticaly it can be dangerous in some cases:

Some one walks over a cord and falls down and breaks something.
There is a water leakage somwhere near and you risk a short circuit.
Somebody can plug it in some other non-compatible device and break it.

But there is no any threat to adapter itself in keeping ac adapter plugged into wall outlet while laptop is unplugged.

Alexander Taran
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I disagree with the power load being minimal. I was trying to track down some powere consumption issues, and discovered that the Dell bricks (for monitors as well as laptops) draw a fair amount of power even when the monitor is switched off. If you want to test this lazily just watch it remain warm even when not connected.

Dangerous - probably not, except as a trip hazard.

Nick Fortescue
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Depends on your definition of dangerous - I love the dicussion here about this.

Something else to consider - depending on how loose the definition of dangerous is - what about the global perspective? From a sustainability view? And the cost to future generations...

A million laptop chargers... chewing though a million watts of power... per hour.. for no real benefit...

I'd say that could be dangerous...

...plus a million more chances of a trip hazard...

or if you're my wife... leaving a sharp knife laying nearby the plugged in power cord, and accidentally sliding it across the work top and neatly into the cable! - I guess that's why we have RCDs

;-) APe

APe
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From https://www.quora.com/Is-it-safe-to-keep-laptop-adapters-plugged-in-I-am-talking-about-just-the-adapter-not-the-laptop-itself

Yes, it’s completely safe in that it won’t damage the device it powers/charges or damage the adapter itself, but there are a couple of (minor) caveats to consider:

1 - As the other respondents have mentioned, any AC-DC power adapter/charger that’s plugged into an outlet consumes a small amount of electric power even when it isn’t plugged into the device.

2 - Leaving an adapter plugged into an outlet 24/7 increases the odds of it getting fried by a direct lightning strike on the incoming power grid. I’ve seen this happen several times over the years.

The above being said, I personally choose to leave my adapters/chargers plugged in 24/7 in spite of those caveats for the sake of convenience. Besides, the risk of lightning damage can easily be mitigated a great deal simply by using a quality surge protector or UPS.

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I don't like leaving a laptop supply plugged in, because some power connectors have exposed contacts and if they hit a metal desk or chair leg, they may short out. It's not likely to start a fire, but it will usually kill the adapter.

The good adapters will be wired with a coaxial connector with the hot end on the inside (most Dells). Some will not. USB power connectors, more common now, are relatively safe as well.

dmoisan
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From my knowledge a transformer works by sending current through a coil which induces a current in a coil thats located very close to the initial coil. This is how you reduce the power from 120v to 5v, or whatever. So, even though you disconnect your notebook, there is still current running through the block. There just is no current running through the secondary circuit, which the primary (house) circuit is creating.

At least, that's what I remember.

My point is, that the brick probably is using the same amount of power, always.

kshaeta
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