My computer guy told me to leave mine on all the time, so I tried it, and besides the fire fear thingy I also ran into several problems. For one, a lot of the times I was told to reboot for this thing or that. Then too, I'd have to reboot when things got too slow or would freeze up. I'm on dialup and AOL if that matters. Another thing is that we have power surges and outages WITHOUT storms around here. So, I just turn it on when I use it, and off when I'm not using it. And I just recently found out that my computer guy now does it this way too.

 

The only component of a PC that is high-voltage is the power supply - I've seen many of those fry before and even saw the aftermath of one that was plugged into a 208V source while set on 120V... Never saw one in flames and the case does an excellent job of containing shrapnel...

12V DC and 5V DC running through motherboard and whatnot - low current... A good quality power supply will last for years - so long as it doesn't get choked up with dust and burn itself out...

I shut monitors off though - CRT's, in particular, can be quite hazardous...

There was a batch of computer produced a few years ago that were produced with faulty capacitors - the supplier sold a huge batch of bad capacitors and Dell, HP, and others who were affected didn't know they were bad until, all of a sudden, they get flooded with complaints about computers dying... We have some of the older Dell's at work with bad caps...

 

Yup, any power supply worth its salt will have proper over current and over voltage protection on the output as well as a fuse or circuit breaker on the mains.

The bad caps thing during the late 90s/early 2000s was spread widely throughout the industry. Its affected a lot of companies. Supposedly a stolen incomplete capacitor formula was spread around a bunch of cheaper Chinese capacitor manufacturers - even a few reputable ones as well and the result was millions of failed capacitors.

 

Anything that plugs in to an outlet, whether it's powered on or not, has the ability to start a fire. I really wouldn't worry about leaving your computer on and it starting a fire.

 

The best way to deal with this is a UPS. You can get a good APC unit for about $60. It provides much better protection from voltage spikes and sags than a surge protector, with the added benefit of safe shutdown during power failures. Shutting down at night is not really protection from power surges - they can happen any time.

 

Thanks for the tip. Yeah, my surge protector didn't do dip for me and a power surge blew my computer (OK, so it was time to upgrade my relic, but I just didn't like having to do it, is all). I did buy a more powerful surge protector though, since I didn't know anything about UPS's and APC's. Thanks again.

 

The argument if it is best to leave your computer on 24/7 or turn it off after usage goes back as far as I can remember. Early computers did not generate as much heat as the multiple cores do now. I see you can get new rigs with different kinds of cooling now. But for the moment, all I have is whatever the desert gives me during the cool/cold months and what my evaporative "swamper" can do when it begins heating up. My present one is a Core 2 Duo 2.2 gig I bought in late 2007 and it has to serve both personal and business use for the next few years.

So I leave mine off after usage when not needed. Only my AVAST is set to automatically upgrade after going online. My Microsoft updates are set to manual "select" and I use FireFox just out of course anyway.

During the Summer, it can get well over 100 degrees outside and over 90 degrees in the Office without the swamp cooler going. Why I don't need to find a "cooked" PC. With the swamper on, it will get down into the low 80s and why I only use my computer late at night into early morning. Without the swamper, I can risk having my computer on during the relative late morning coolness. By mid Summer, those times get awfully short.

When thunderstorms are threatening, though, I unplug from the wall to prevent any surges from a close lightening strike. I do not trust surge protectors completely after having a computer and modem "fry" a few years ago from a fairly close strike. Don't want to go through that again.

I keep the insides clean on a regular basis from the desert dust. Also from any residue "smokiness" after my husband "cooks" the coal into "coke" from his blacksmith forge.

 

What I haven't seen mentioned in this thread is notebooks. Those I would NOT leave on 24/7. Those usually have limited cooling capacity, and they benefit from the OFF periods to completely cool. Leaving them on kills the batteries faster too. Just thought I would mention this, since I know some of you use a notebook as your only computer.