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I'm wondering if i were to leave my computer for a short time (perhaps 70 seconds) should I set the computer to go to hibernate or will the overhead of hibernating unhibernating actually suck up more power than if i simply let it run as per normal?

1) is it true that if I have alot of programs running, then hibernating is a costly action (in terms of power) ?

2) is it true that writing contents of RAM to disk takes significantly lesser power compared to reading contents of RAM from disk?

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if you are using Windows, why aren't you considering Sleep? – icelava Aug 14 '11 at 2:27
@icelava when i sleep and i run out of battery, my data is gone. when i hibernate and i run out of battery, my data is not gone after i charged my laptop and re-on it – Pacerier Aug 14 '11 at 2:45
The system is SUPPOSED to recognize that the battery is running down and hibernate if it sleeps for too long. Unfortunately, this logic only works sporadically, at least with Vista on my Sony. – DanH Aug 14 '11 at 2:52
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closed as not a real question by techie007, Sathya♦ Aug 16 '11 at 16:21

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. See the FAQ for guidance on how to improve it.

3 Answers

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For what it's worth, the power used in writing the contents of RAM to disk and then reading it all back into memory probably exceeds the amount used under typical use for 70 seconds.

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btw does it mean that the more programs we have, the more power is needed to write the contents of RAM to disk? – Pacerier Aug 12 '11 at 8:15
When you hibernate your laptop, it needs to write the contents of physical RAM to your hard disk (so that it can read it back later). Generally speaking, more programs = more RAM in use = longer hibernate process. Hibernating is power-intensive because, during that copying process, the hard disk is running non-stop, unlike normal idle operation where the hard drive is only spinning up occasionally if at all. – jcrawfordor Aug 14 '11 at 3:36
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You're asking a confusing question. If you have a lot of programs "running" (and not simply idling) then the laptop is consuming a fair amount of power.

However, if your computer is idling, with the display and disk drive turned off, and the power management logic is working right, it should be using very little power -- essentially just enough to keep the memory "refreshed". Writing memory to disk (hibernating) requires spinning up the disk drive, operating the access arm, and cycling through memory -- operations that will consume maybe 100 times the power used while idling. And similar power will be required when leaving hibernate.

As a thumb suck, I'd say that it doesn't pay to hibernate (vs "sleep") unless the system will be unused for more than an hour.

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which part of the question is confusing? i'm sure power is needed for everything, so basically the question is comparing the amount of power needed to hibernate the computer when it has alot of processes running to the power needed to hibernate the computer when it has a lesser amount of processes running, which will require a lesser amount of power? – Pacerier Aug 14 '11 at 2:58
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actually, if you are really that hungry to know the exact energy consumption for these activities, i'd recommend you obtain a wattage monitor and witness the hard evidence for your own eyes the energy drain of constantly hibernating and resuming your laptop.

http://www.codinghorror.com/blog/2008/04/revisiting-how-much-power-does-my-laptop-really-use.html

You should then take a rough calculation how many times you'd hibernate/resume in a "journey" and the energy cost summed up, compared to just sleeping.

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