How much energy does a "brick" power cord take?

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Misha Cohen Author

Level 3

735 points

How much energy does a "brick" power cord take?

Hi,

1. How much energy does the White Brick power cord consume when the computer is fully charged?

A. Does it vary based on processor action?

B. How bout when the computer is sleeping?

C. How bout when the computer is off?

2. How much energy does it consume when it's not attached to the computer?

A. I also want to know this for chargers for other Apple devices.

Thanks for any info on this. I haven't done any searching on this, so maybe it's an obvious question.

Mac OS X (10.7.5), 17", 2.4 GHz Intel, 8 GB RAM

Posted on Nov 8, 2013 3:59 PM

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Answer 1

carl wolf

Level 6

14,631 points

Nov 8, 2013 4:46 PM in response to Misha Cohen

"maybe it's an obvious question."

The answer, not the question, is obvious. Every power adapter is rated in watts, and that's the maximum power that the power adapter will supply reliably. Accrodingly, if the power adapter is rated "85 watts", that's the answer.

An Apple power adapter consumes electricity if it is plugged into an AC outlet, even though it is not attached to a device.

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Answer 2

Misha Cohen Author

Level 3

735 points

Nov 9, 2013 3:43 PM in response to Misha Cohen

I want to leave this question up still. I would like an affirmation of what carl wolf says.

Also, if the white brick is rated as "up to 85 W" then does that mean while the computer is sleeping or off or unplugged it uses less?

Thanks.

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Answer 3

sanjampet

Level 5

7,988 points

Nov 9, 2013 3:58 PM in response to Misha Cohen

It maintains a steady state current to provide the power circuit with the amount of power it requires, it is for the most part a transformer, and thus transforms (AC to DC) now the the draw on that device vs the demand will change it's draw slightly, but is is always transforming.

If you are in the states your 85w xformer will have a max draw of 1.3 amps(at a median voltage of 115VAC), but this will fluctuate as to what the charge circuit in the battery/charge circuit is "asking" for to maintain the steady state, thus sleep, off, and depending on the compute cycles required to run particular process(s) will become dependent, as to what is needed. The Mac has a power management system in place.

Depending on on battery status/health/and many other factors. This is as simple as I can put it, you can go online and go on to some of the EE sites and I'm sure you will find the mathematical solutions to the equations you seem to be searching answers to. They would fill pages here.

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Answer 4

sanjampet

Level 5

7,988 points

Nov 9, 2013 4:24 PM in response to sanjampet

carl wolf basically explained it.

Some reading here:

http://askville.amazon.com/transformers-12v-6v-draw-current/AnswerViewer.do?requ estId=2607770

http://answers.yahoo.com/question/index?qid=20110331075711AA7T9Pv

http://kurratul.weebly.com/uploads/3/3/4/6/3346099/transformer-2.pdf

http://wiki.answers.com/Q/What_is_no_load_current_in_a_transformer#slide1

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Answer 5

sanjampet

Level 5

7,988 points

Nov 9, 2013 5:51 PM in response to Misha Cohen

Was there anything that helped you?

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Answer 6

Misha Cohen Author

Level 3

735 points

Jan 11, 2014 3:45 PM in response to Misha Cohen

Thanks for these answers. I neglected this post for a while as I didn't have time to investigate. The answers were helpful.

I did find some more information:

https://discussions.apple.com/thread/1359172?answerId=6423752022#6423752022 lists (for a 2008 macbook) the consumption. I would be interested in seeing this for the latest models. Especially interesting is this: "Power brick energized, but not attached to computer - unmeasurable." Is the power adpater (it's a transformer) this energy efficient? This is a big deal if I am planning on unplugging my laptop at night.

I also see this: https://www.apple.com/macbook-pro/environment/ . But, unfortunately (and outrageously), it does not give details (it is not outrageous as a status quo piece of marketing, but it's outrageous that the status quo is that little information! So, the problem is not Apple, per se, but the habits. Maybe that is an area for a marketing company to improve on!

I found this for some more, general information: http://electronics.howstuffworks.com/everyday-tech/plug-in-transformer.htm . That gives: "The power consumption is not large [on power chargers] -- on the order of 1 to 5 watts per transformer."

I'd certainly be interested in information on Apple's other products (like iPod and iPhone chargers).

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Answer 7

Csound1

Level 9

60,063 points

Jan 11, 2014 3:52 PM in response to Misha Cohen

No load equals no power transfer, so, apart from what little current is drawn by any circuitry in the charger itself there will be no power used.

Load it with a Mac and it will draw whatever its rated output is unless the Mac is fully charged, and switched off.

Sleep mode is less than 2W

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Answer 8

Misha Cohen Author

Level 3

735 points

Jan 11, 2014 4:00 PM in response to Csound1

No load equals no power transfer....

Sleep mode is less than 2W

Do you mean for a macbook pro power adapater brick? Or for all electronics? The key here is "power transfer." If energy is used, there is no power transfer to an object. However I am asking about the energy used. (I want to make this clear for people reading this.)

"No load power draw" is a rating term that means, from my little information, "the amount of power drawn when there is no object attached to the transformer." And you mention that it might be up to 2W in sleep. That would be the figure I am curious about for various products.

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