Charging a computer: power adapter output

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Discussion Overview

The discussion revolves around the power consumption of a MacPro Apple computer when using an 85 W power adapter. Participants explore whether the computer consistently draws the full 85 W or if the power usage varies based on the number of programs running and other activities.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions if the power drawn by the computer is always 85 W or if it fluctuates with usage.
  • Another participant provides information suggesting that a fully charged laptop uses about 24 W, while recharging may require around 37 W, indicating that the adapter is sufficient for typical use.
  • There is a discussion about the components of the computer that consume power, with emphasis on the disk, screen, and CPU/memory, noting that power consumption can vary based on activity.
  • A participant mentions that some CPUs can adjust their speed based on processing needs, affecting power draw and heat generation.
  • One participant calculates the cost of power based on the adapter's rating and expresses confusion about the perceived expense of electricity in relation to actual usage.

Areas of Agreement / Disagreement

Participants express uncertainty about the exact power draw of the computer, with some suggesting it varies based on usage while others provide estimates of typical power consumption. No consensus is reached on the specifics of power usage versus adapter rating.

Contextual Notes

Participants discuss various assumptions about power consumption without resolving the complexities of how different activities impact overall power draw. There are also references to costs associated with electricity that may depend on local rates.

fisico30
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Hello Forum,

I have a MacPro Apple computer. I just got a new power adapter rated 85 W.
Does it mean that the computer is always drawing 85 W of power does is the power delivered depend on how many programs are open, etc...?

thanks
fisico30
 
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I see, thank you.

this one was given to me at the Apple store. I guess I was wondering if it continuosly have to draw the amount of power written on the adapter or it depends on the computer activities...
 
the key parts in a computer the cpu/memory, the disk and the screen with backlighting.

The disk probably draws the most power so constant disk access will drain your battery faster.

Next the lit up screen followed by cpu/memory.

Some cpus can change speeds depending on the processing requirements so a faster speed chews up more power, generates more heat and may cause a fan that also draws power to run.

The most power saving mode is to turn the laptop off and use a piece of paper and pencil. :-)
 
fisico30 said:
I see, thank you.

this one was given to me at the Apple store. I guess I was wondering if it continuosly have to draw the amount of power written on the adapter or it depends on the computer activities...
In general adapters are designed to handle the maximum plus a safety margin.
 
Ok thanks. I guess we found the answer: if the adapter is rated 85 W, and 1 KWh of energy costs around 15 cents, it does not mean that in 1 hour

85 x 1 hour ÷ 1000 x 10 cents per kWh = .850 cents ?

Ok that sounds like nothing, not even a cent? And we are saying that the computer may not even be operating in such a way to be always requiring 85 W, sometimes less...

They say power is expensive? Where is my mistake?

thanks
 

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