power off or not power off a pc

[tania]

some people told me not to power off my pc, others told me to do it.
I'm a bit confused...

Thanks for helping,

Tania

[Charles Howse]

Previously tania <tania@ligo.mit.edu> wrote: some people told me not to power off my pc, others told me to do it. I'm a bit confused... Thanks for helping, Tania

Some aspects of the question:

Europeans often shut down their PC's at work for the night to conserve
energy. Americans usually let it run. A idle PC consumes in the range
of 100-150W, that is 2.4-3.6kWh/day.

There are rumors that HDDs live longer if the are kept running.
Historically that was true, because on every start-stop cycle the
hdd heads would smoothen the surface a bit more when landing.
Eventually they would stick and th HDD would stop working. Modern
HDDs have a coating that prevents this problem. With the 50.000
start-stop cycles a moderd desktop HDD supports that is not an
issue anymore. Laptop HDDs have 500.000 start-stop cyccles, so
they can be even put into sleep mode after being idle for some
minutes.

Semiconductors that run very hot will die earlier, usually halving
the lifetime for every 10C. If operated in spec, you will still get
5-10 years. Overclocked CPUs may die a lot sooner. No manufacturer
does overclocking, so if you did not do it yourself, you do not
have it.

One factor that definitely figures is capacitor lifetime. Capacitors
are critical components in the power supply and voltage regulators for
the processor. Their lifetime is very much dependant on the
tempereture, since the liquid in them evaporates faster when they are
warmer. Eventually they explode (not dangerous unless you are staring
at them when they do it). I have measured up to 65C on capacitors on a
mainboard that was running. Gives about 3-5 years operating lifetime
with good quality caps, maybe as little as 1 year with cheap ones.

The other thing that wears is the bearing in the fans found in the
power supply, on the processor and today often on the graphics card.
They have a life-expectancy between 10.000 and 50.000 power-on
hours. The problem is that cheaper ones will start getting noisy a
lot earlier, maybe as soon as 5000 hours. That is > 2 years with
6 hours/day, but only 6 months when running all the time.

Because of the later two factors and because of energy conservation, I
would advise to shut it down, unless you have a good reason to keep it
running.

Monitors (LCDs as well as CRTs) should allways be shut down or put
into sleep mode when not working for a hour or more, since they loose
brightness when on. They might not break, but will get dim pretty fast
when they are always on.

Hope this helps,
Arno
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