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I have a laptop with a recharger (also known as an AC adapter), this is how it looks like:

enter image description here

When I disconnect my laptop from the charger, does it (the charger) still consume (waste) electricity?

EDIT:

I am trying to do math, how many kW I waste every year to keep my adapter plugged in the whole time. I tried to read how much watts does it take, but I am not good with that kind of stuff, so here is some info:

INPUT : 100-240V~50-60Hz 1.5A(1,5A)

OUTPUT: 19.5V(19,5V) --- 4.62A(4,62A)

Does this info help to do the math?

There is 8760 hours in year.

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4 Answers

up vote 5 down vote accepted

Yes. Generally anything with a transformer in it will draw at least some power when plugged in. See here for more details on the types of devices that will typically use power even when off. The only thing that will keep a device from drawing standby power is if you actually break the circuit that the device is plugged into.

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But how much? I added some text from the adapter, I am not sure if those are right numbers, since I only found volts. – Jaanus Sep 27 '11 at 5:01
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@Jaanus you'd need to measure it. The exact amount of idle current is dependent on the the implementation details. Mostly in that cheaper devices will draw more power for the save level of functionality. Unfortunately for consumer level hardware this is easier said than done because idle power levels are similar to both the base error level and granularity of inexpensive power meters like a killawatt. – Dan Neely Sep 27 '11 at 12:58
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up vote 3 down vote

I just did a test with my P3 watt meter. One old DELL adapter (10+ years, for Latitude P3 650) uses 1.3W while the laptop is not connected. However, a recent HP adapter (2+ years) uses 0 W (at least from P3 watt meter reading).

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up vote 2 down vote

Yes, not a whole lot but over time it does add up. It can also wear out the transformer sooner.

See http://electronics.howstuffworks.com/everyday-tech/plug-in-transformer.htm for more info.

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modern laptop power supplies are switching power supplies – Journeyman Geek Sep 26 '11 at 22:46
But how much? I added some text from the adapter, I am not sure if those are right numbers, since I only found volts. – Jaanus Sep 27 '11 at 5:01
The article I refer to shows you how to calculate it. – bryan Sep 27 '11 at 5:06
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up vote 0 down vote

Yes it will, if the switch on the wall is on it'll use electricity.

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A trivial amount, mind you. – Shinrai Sep 26 '11 at 19:29
Can you maybe explain why this is? – slhck Sep 26 '11 at 19:30
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@slhck The main reason with older bricks is that use of transformer coils that need a steady supply of power to remain energized. Newer devices normally use switched mode power supplies which have much lower idle current levels unless constrained by something attached to the output like a status light to indicate that it's plugged in and drawing power. – Dan Neely Sep 26 '11 at 20:31
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@DanNeely That's what I'd like an answer to contain. Why not post your own one and explain a bit? – slhck Sep 26 '11 at 20:32
@slhck the other source of idle power draw is for devices that never turn off completely. This is anything with a push button switch instead of a toggle switch. At a minimum they're drawing a small amount of power to detect the switch being pressed. In many cases they also keep capacitors/etc charged to be able to start up faster. In addition to faster startup this design has become common to avoid routing AC power from the plug to the front of the case both as a safety feature (less likely to be shocked by a failure) and to reduce costs (thin wires to the switch instead of thick wires). – Dan Neely Sep 26 '11 at 20:35
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