should we REALLY turn pc's off at night? I don't think so.

Yes, I recommend turning off the PC's. We will save several nuclear reactors doing so. And CO2 emissions will be reduced.

The failure rate will peak shortly, but a la longue the weak spots will be eliminated and the whole system will be more stable.

Otherwise the breakdown of components will always occur during work at the worst possible time.

w.

Stick an ammeter in series and see how much it draws.

yes, keeps internet scum out of your computer, saves about 3 amps * 120 volts * 12 hours = 4 kilowatt hours per machine keeps voltage surges out too PCs are designed and built to be turned on and off. your hard drive is always getting hammered when the PC is on.

Seems more logical to use power-saver modes. I do that with my desktop at home, which I rarely use anyway. So when I'm not using it, I shut it down with (Windows XP) hibernate mode rather than a full shutdown. No power consumption, and a much quicker restart. Of course, Windows being Windows, after 4 or 5 cycles the behavior starts getting flaky and I have to do a true reboot, which takes a good 5 minutes on that computer.

Lots of computers have power management, where they will shut down the screen or the hard disk when idle. Are you saying that power management decreases lifetime of the disk?

- Randy

Not really true - lots of PCs fail from fans wearing out, or from electrolytic capacitors wearing out. Neither wears out when the power is off.

It does. A PC that with the disk spinning but otherwise idle uses 100 watts, maybe uses 200 watts when doing something like booting.

Thus, if it takes 1 minute to boot the PC, you save power if you leave the PC off for more than a minute!

True hibernate saves the state of the computer to disk and then switches off power. That state is equivalent to 'off' from a power use perspective - it is even possible to unplug the computer. Waking up from a hibernate is not a real boot, thus you do not gain the advantages from the occasional reboot.

Other sleep states exist. For example S3, suspend-to-ram, isn't bad - on a laptop at least. Only the RAM stays on, but if the power supply needs to keep running for that, the power use may still be quite high.

As for hardware failures: PCs are designed to switched on and off every day. The part that might wear out from this is the hard drive, but that problem has long ago been tackled.

Thomas

If you turn off the PC's at night, how do you do the nightly corporate upgrades/patches/security fixes/virus scans/backups?

It becomes a tad more difficult, but someone invented 'wake on LAN' for that.

Thomas

In 1977, I personally did a study of this issue. I found that the increased computer failures on power up/down cycles were due to poor power supply and disk controller designs, Power supplies should ramp power down over at least several seconds. The first step in power down should be to park the disk drive heads. The last step in power up should be to mount the heads.

If the above rules are followed, computers systems show no increased failures with power cycling. Cheep computer designs with on/off switches that merely interrupt the AC power will show increased failures. If you have made the mistake purchasing one of these, consider adding an uninterruptible power supply system to your computer. UPS systems will ramp the AC power up and down, which is a second best to a properly designed power supply that ramps the computers DC power, but better than no ramping of power at all.

It's a tradeoff, like anything else. There are impacts on PC reliability due to power-on/power-off transients, not to mention the thermal cycling that goes along with this. But on the other hand, simply operating the thing normally ages it as well, in addition to wasting a good deal of power. What you need to do is to strike a balance between the two.

A once-a-day on/off cycle generally isn't going to have a huge impact on reliability, and assuming the "off" period is long enough (overnight - 8 to 12 hours, say) provides more than enough in power savings, typically, to outweigh the reliability hit. I would not recommend turning your PC off and then back on every time you go to the restroom or break for lunch or similar short-term situations, but overnight - sure, it's probably worth it. The savings can be considerable - it's a rare PC system that isn't consuming a few hundred watts in normal operation, so multiply that by the number of PCs on your site and the number of hours they're sitting idle. Then call the power company to see how much those kilowatt-hours are costing you, and think how many PCs you could afford to replace with that money - IF you even needed to - should you see the occasional failure.

A better option, though, may be one that's already been mentioned. Use your PC's power-savings features to enter a low-power "standby" or "suspend" state during those long idle periods. This generally doesn't involve quite the several on/off transients that the complete shutdown or power-up does, but can often still give you almost the same level of power savings that the "hard" shutdown will. You especially want to make sure that the real power hogs in the system, such as the display (and often the printer, esp. laser printers - these have an electrically-heated element to fuse the toner which is just burning power when it's on but idle) are shut down or at least in a very-low-power standby state when idle.

Bob M.

Eventually you WILL be turning off PCs at night. The question is moot.

Expect your power costs to rise exponentially when carbon taxes are put in place and your power companies have to start retooling in order to comply with government legislation designed to cut down CO2 emissions.

Your power costs will rise until the users meet the targets set by Kyoto.

Things have changed a bit since 1977. Disc drives then were few and far between.

When mine is on I see 2 LEDs, for the disk drives. You can run an LED for weeks on a single AA cell. I think that we can discount the power required to run the LEDs. The disks appear to be spinning and the fan running. The power required to do this is very small, comparable with a battery operated toy. Unless the electronics are somehow using significant power which is not released as heat the total consumption must be pretty small.

Plus, even though computer components may be stressed out a bit, I doubt people will keep a PC for longer than 5 years anyway before buying a new one. So, fan life and capacitor life only has to be good for about 5 years.

Hard drives, though, are a different story. External backups of critical data are a great idea.

Michael

Well, if it stays powered, it gets no 'hit' from being powered off and on, but the savings will be minimal as well.

I think laser printers are not that bad any more, with energy costs and what not. Processors have gotten worse, and only recently started improving again.

Oh yes, don't forget the screen saver. They prevent the processor from idling and thus waste a lot of power.

For that matter, things like speedstep and power now will give thermal cycling for the processor and its power supply. It doesn't care.

Thomas

Backups are of course needed. But power cycling an IDE drive is not bad for it. Actually some IDE drives are only specified for 8 hours of power-on usage per day.

The Seagate Barracuda 7200.10 is rated for 50K contact start-stops. If cycled every hour, you could go on for 5 years.

Thomas

All of my statements below are still true.

I am a career computerist. (Yes, it's a word.) So I am a bit ahead on these things. My first personal computer was a homebrew made in 1969, it used random access tapes. I interfaced a hard disk to my home computer in 1975. It think the tape cassettes each stored about 100K bytes in 50 numbered files and the disk a bit less than a megabyte.

I still have some of the hardware, and it still works. I also still have every byte of the data that I archived on those tapes, though they've been stored on more than a dozen different media since then.

Maybe so but disc drives were not readily available then. You didn't order your hard disk from Sears or Radio Shack did you? I think not. You borrowed a few things from work. Congrats on preserving the data so long. You realize it will never be getable unless the same format is still being used and there is hardware and software to access it don't you? Keep that homebrew stuff from rusting.

Hi Zak ( a.k.a. Thomas ) and Paul,

I've been using PC's ever since 1981. I turn my PC off whenever I'm not using it, several times per day.

Not only does this reduce wear on the fan, the fresh boot insures that your system runs consistently.

My PC ( a bottom-of-the line, HP/Compaq Presario, with a Celeron CPU ) is at least 3 years old, and it boots in 22 seconds ( I just timed it ).

While they are gone to lunch.