So, my computers have always stayed on. No matter what time it is. It’s more of a force of habit than anything. But something someone said to me is what I’m trying to find some validity behind. They’ve said that you use less energy keeping your computer on, than to spike the electricity from turning it on every day. Now, that doesn’t sound like it’d be right, but I remember more than one person in my life telling me not to flick lights off and on too quick and too many times for the same exact reason. So, there’s my question: Does it take more energy to keep a computer on or to turn it off and on every day, sometimes more than once a day?
The answer is that it depends, but I suspect that energy usage isn’t the issue - it is with fluorescent lighting, as this consumes a lot of power in starting up, hence the advice to leave it on if you’re only leaving the room for a short period - AFAIK, the initial power drain of a typical PC is nowhere near as significantly different from the power required to just run it.
However, electronic components are more likely to fail (or be damaged) when they are being switched on or off, so leaving your computer on all the time should reduce the probability of component failure, except that other components with a finite lifetime will be ‘used up’ more rapidly.
If your machine is set up to use power saving options though, the whole issue may be rather moot, as having the machine switch off its own components isn’t a whole lot different to switching them off yourself (OK, maybe it is a whole lot different, but it still might induce failure).
Another issue is thermal stress - a machine that is repeatedly subjected to cycles of warming up and cooling might suffer mechanical or electromechanical problems such as poorly seated connectors and failed/intermittent solder joints.
So there are pros and cons either way - accurately quantifying these is difficult - a lot of it will depend on how much usage the machine is being put through - if we’re talking about a family media/home entertainment system that incorporates computer, HiFi, TV, DVD player and gaming, it is likely to be used on and off throughout the full range of working hours - leaving it switched on might well be better than turning it off and on thirty times a day (it may cost more to run, but less to maintain/repair.
but if we’re talking about a home office machine that is used for two or three hours each evening and not at any other time, then leaving it running for the remaining twenty-odd hours is probably wasting more money in electricity bills than you might save in maintenance.
This question of wasting power by turning something off because of the starting surge comes around all the time. For a computer, there is some cost to turning it on because it takes a couple minutes to boot (UNIX even more). So you probably don’t want to turn it off to save power unless you are away for at least ten minutes. I once worked it out for fluorescent lights and the time came to something like seven seconds. For incandescent lights, it is a fraction of a second. For most other equipment, it will be between those times.
A completely different question is the wear and tear on the equipment. Many years ago, I was the operator of a large analog computer and we had a turning on sequence to let one part stabilize before turning on the next. This was mainly to save the vacuum tubes, which were continually burning out. In retrospect, I think we would have done better to have separate power supplies for the heaters and have them come up to voltage slowly. As for modern computers, I have heard different stories and I don’t know what to believe. Sun makes it clear that their computers are meant to be operated continuously. PCs seem to be designed to be turned on and off daily and it will certainly save power to do so.
You have doubtless noticed that light bulbs mostly burn out when you turn them on. But I think that such bulbs are about to burn out anyway. The real question is whether each turn on shortens the life of the bulb. I’m sure it does, at least a bit, but I have no idea if the amount is significant.
As far as power goes, shutting it down is a good thing. The initial boost is not a big deal. However, I would not leave it on all the time largely for the issue of the Hard Disk. If you plan on being away for 8 hours or more, shut it down.
TRheoretically, you will get a longer life out of your HD by leaving it on - but then, that will actually be a lot less utility. See, the actual lifespan of the component will be longer, but you’ll be using that time up a lot faster. So shut it down.
I leave my computers on all the time. I use Windows’ energy saver to turn off the monitor, but that’s all. If I know I will be gone for more than a weekend, I shut the computers off, but that’s rare. If you are worried about extending the hard drive’s lifespan and usability, you can have it go to sleep after an hour or three. The reason I leave my computers on is that all four of them have millions and millions of unbelievably tiny wires and components that heat up when I turn the computers on, and cool off when I shut them down. When that happens to most materials enough, they fatigue and wear out/break (as in the light bulb example someone already mentioned). Leaving the computers on (in my opinion) extends their “lives” compared to turning them off and on every day. At any rate, it’s generally not recommended that you shut your computers down completely and switch them back on more than a few times per day to minimize the wear on all those incredibly small parts.
There are two schools of thought on this . . .
Cecil’s column on the energy consumed by turning lights on: http://www.straightdope.com/classics/a1_249.html