Pro's and Con's

Hi,

Apart from the obvious reason that many people leave their machines on - for continual use, there is another reason many people aren't aware of...

Its called thermal stress. When a machine is on, it warms up and the components expand slightly. When the machine is turned off, it cools and the components shrink again.

Over many cycles, the components themselves become fatigued and can microfracture ultimately causing failures.

Its kind of like breaking a piece of wire by repeatedly bending it back and forth but obviously far less severe!

The other problem with powering on systems is the inevitable power spike the moment it powers up before it reaches a steady state. This puts extra pressure on components and can cause a breakdown in the insulators within those components.

Leaving it on does wear it out, though. Especially the moving parts like fans. Its wise to regularly check your fans on machines that spend large amounts of time on.

Also the solid state components eventually break down - or at least those good old insulators within them do...

Another obvious disadvantage is cost. It takes power to run it and if its nott being used.

Overall components these days are manufactured pretty well and so for a home machine, its really personal preferance as to what you do.

Hope this helps,
Cheers,
Tim.

Tim gave you a good review from the hardware side.
I agree with all that he wrote.

The only thing that I can add from the hardware side, is that the monitor is the big power user for a system that is idleing. A computer that is idleing uses less than 60 watts of power. If you allow it to go into standby mode, or hibernate, the power usage is even less.

From the software side, there are a couple of factors to consider:

Do you have a DSL or cable connection?
Unless you disable the connection when you are away from the PC, leaving the PC on increases your chances of being hacked.
Maintaining your firewall and other security measures becomes critical.

Windows 9X has a tendancy to gather memory leaks.
In fact, there is a knownbug where the system can hang after 49.5 days of constant operation.
Using memory leak control software is a good idea in a 9X system if you are going to leave it on constantly.

If you decide to leave the PC on constantly, you can use task scheduler to perform all those maintenence tasks that you never seem to get around to.

As Tim said, it really does boil down to personal preference. We treat our PCs like any home appliance. We turn it off when we are not at home, or when we go to bed. At a minimum, for saftey sake, I would turn off the monitor for those times.

Chas & Tim both brought up some very good points. The two extremes are to always turn your computers off unless you are actually using them or to never turn them off.

Turning off and on does add thermal stress, as mentioned by Tim, so only having the computer on when you are actually using it can add a lot of stress to the computer, not to mention the stress on you waiting for Windows to get its act together at each start up. For those reasons I prefer to turn my computers on once a day.
Leaving them on all of the time when they are unattended (like when you go to sleep) does have some negative considerations. As mentioned, power consumption continues. There is a small, but added fire hazard. There also is the added exposure to damage from power interruptions or power line problems. I would highly recommend a UPS no matter when you leave your computers on.

Turning the monitor off (like at night) is highly recommended because of wear on the monitor, whether LCD or CRT, and heat/power consumption for CRT (regular type) monitors.

Wear on the hard drive assemblies may be more important that the wear on the fans when the computer is on all the time. Hard drive failure is not pleasant at any time.

Answer 1 is a great explanation of why it is fine to leave it powered. If your machine is running cool enough with the proper fans/cooling grid it should be fine. However if you are running Windows 98 it is known for "leaking" resources. In otherwords, the longer is runs the less memory is available for use. You may notice the mouse acting strange. Programs loading slowly or not at all. I usually cold boot once or twice a week to reset the resources. This is a Windows issue and not hardware.

Rick

This question pops up now and again, and no one seems willing to take a stand. Turn your PC off! In an office environment leave the PC on all day, then turn it off when you leave. This is the rule in my office. At home, it's only on when I need it. What the other answers said about wear is ture, sort of. Yes, turning on and off a PC can and does stress the components. But, PC's are far more durable and reliable than they were a few years ago. Check the MTBF (mean time between failures) rating on hard drives compared to older HD's. Chances are, you are going to replace you PC or it's components long before they fail. I've been using the same computer case since 1987 and i keep ugrading the parts. The only part that I've ever replaced because it died was the first CD-ROM I put in. Everything else has been an upgrade.
Leaving the computer uses more energy, leaves you open to hackers if you have DSL or cable, builds up memory problems (the above leaks that all software seems to have), leaves your computer open for other people to "snoop" if they find your computer left on.
Turn it off when you're done.