Home > Computers and Internet, Hobbies > How long to Sleep vs. Hibernate a computer

How long to Sleep vs. Hibernate a computer

In Windows 7 there are two general ways to send a computer to a low power state when it is not in use: Sleep and Hibernate. For more details on both see Sleep and hibernation. I’ve always favored hibernation, but lately have felt that if I’m planning on using the computer again in less than eight hours to sleep it instead of hibernating. Eight hours was just pulled out of the air, no real science behind it. The other day I was talking with a friend and he felt that eight hours wasn’t long enough. He asked if I knew how much power the computer was using when sleeping, and I said I did not. So to find out for sure I purchased a Kill-A-Watt and have ran some tests. I wanted to know how much power sleeping my desktop took.

  • Computer on, low CPU:113 Watt
  • Sleeping: 15.5 Watt
  • Time to resume from sleep: 6 sec
  • Time to Hibernate: 33 sec
  • While hibernating: 13.4 Watt
  • Resume from Hibernate: 38 sec

Hibernation isn’t supposed to take any power, and it doesn’t. The power usage for when the computer is hibernating is the same as when the computer is off. But when I ran these tests I left the speakers on and in between everything else plugged into the power strip, that’s what the power consumption is. I figured this configuration would result in the most worthwhile numbers.

During both going to sleep and hibernating, as well as resuming from both, the Watt usage is higher than when the CPU is idling. It generally fluctuates between 130 and 150 Watts. I don’t have the resources to calculate exactly how much power was being used at any given point, so I’m going to have to assume that power consumption for resuming from both are the equivalent.

So with my rough calculations I get that the extra overhead of sleep is 6 sec * 130 Watt = 780 Watt seconds. Cycling through a Hibernation is (33 sec + 38 sec) * 130 Watt = 9230 Watt seconds. The difference between the two is 8450 Watt seconds. 8450 Watt seconds / 2.1 Watt = 4023.8 sec = 67 min.

Looks like my eight hour gut feeling was pretty far off. The point where hibernation begins to consume less power than sleeping is a little over one hour. Of course there are other things to consider like:

  • the Watt usage during any given second of resuming from hibernation is probably higher than resuming from sleep
  • The cost of my time to wait for resuming
  • Resuming from hibernation is “harder” on the system than resuming from sleep

So I don’t think I’m going to change my eight hour guideline. Now at least I have an educated guess as to when hibernation makes more sense than sleeping does.

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