Power Supply question

[John Smith]

I'm planning on building a new computer but I have a quick question
about the power supply.

Comparing a 300W power supply with a 400w power supply, does that
automatically mean the electrical bill will be increased by 25%?

Or does this instead mean the power supply is capable of 'producing' up
to 400w of power when the load requires it? If this is the case, what
are the disadvantages of buying a psu that is rated too high for what I
actually require (besides initial cost)?

 

[kony]

I'm planning on building a new computer but I have a quick question
about the power supply.

Comparing a 300W power supply with a 400w power supply, does that
automatically mean the electrical bill will be increased by 25%?

No, switching power supplies only consume the amount of power needed.
There is a very tiny/trivial increase in efficiency as these power
supplies supply nearer and nearer max capacity, but not significant
and would result in shorter lifespan.

Or does this instead mean the power supply is capable of 'producing' up
to 400w of power when the load requires it? If this is the case, what
are the disadvantages of buying a psu that is rated too high for what I
actually require (besides initial cost)?

Cost is the only significant disadvantage. Buy name-brand quality,
and 400W should suffice for anything but the most power hungry P4 with
over half a dozen hard drives and a dozen fans, etc. If using a small
case with no possability for a lot of drives 400W isn't even needed,
so long as you buy a name-brand with a capacity rating you can trust
(which excludes Enermax, BTW).


Dave

 

[El Jerid]

No, switching power supplies only consume the amount of power needed.
There is a very tiny/trivial increase in efficiency as these power
supplies supply nearer and nearer max capacity, but not significant
and would result in shorter lifespan.


Cost is the only significant disadvantage. Buy name-brand quality,
and 400W should suffice for anything but the most power hungry P4 with
over half a dozen hard drives and a dozen fans, etc. If using a small
case with no possability for a lot of drives 400W isn't even needed,
so long as you buy a name-brand with a capacity rating you can trust
(which excludes Enermax, BTW).

Don' t underestime the required power, nor your future upgrades.
The link hereafter will give you a good and easy calculation of your
required power.
http://www.challenge-my.com/goopsulator/

 

[DaveW]

It will only draw the wattage that it needs. And it just costs more. But
get a good quality PSU (Antec, etc.) because the cheap ones do NOT produce
their rated power.

 

[kony]

Don' t underestime the required power, nor your future upgrades.
The link hereafter will give you a good and easy calculation of your
required power.
http://www.challenge-my.com/goopsulator/

That calculator is technically flawed in several ways. Using it will
cause a needless waste of money on a higher wattage than necessary,
which is part of the reason some people end up with "budget" generic
power supplies that claim 500W but can't do 300W with a tailwind,
since a good name-brand 500W PSU is big bucks, but the more affordable
generic 500W is often worse than a name-brand 300W.

For example, I just entered the numbers for one of the systems I have
here, which it claimed needed almost 500W even though it drastically
underestimated the o'c CPU and the o'c video card. IF that calculator
had taken these two items into account on th3e same measure as the
other items, it would've probably claimed 600W needed. That system
has ran fine for over a year on a 300W power supply, zero problems.
Granted it's a very good 300W power supply (Liteon server), if I were
to replace it I'd get a 400W Sparkle.


Dave

 

[El Jerid]

That calculator is technically flawed in several ways. Using it will
cause a needless waste of money on a higher wattage than necessary,
which is part of the reason some people end up with "budget" generic
power supplies that claim 500W but can't do 300W with a tailwind,
since a good name-brand 500W PSU is big bucks, but the more affordable
generic 500W is often worse than a name-brand 300W.

For example, I just entered the numbers for one of the systems I have
here, which it claimed needed almost 500W even though it drastically
underestimated the o'c CPU and the o'c video card. IF that calculator
had taken these two items into account on th3e same measure as the
other items, it would've probably claimed 600W needed. That system
has ran fine for over a year on a 300W power supply, zero problems.
Granted it's a very good 300W power supply (Liteon server), if I were
to replace it I'd get a 400W Sparkle.

I used the calculator for my personal PC (heavy video editing). When looking
at the total rail power (light blue), I get 340 Watts . Because this is at
100 % load, I don' t need the default adjustments of 80 %. For security
reasons I could take 90 %, which gives a recommanded power of 380 Watts. I
think that for the system I have, this value is very realistic. Of course,
this does not exclude the fact that some PSU's can better "hold" the power
than others. And that's where the adjustments come in. If you have an Antec
or Enermax (that's mine), no need to adjust.

 

[Ken]

Comparing a 300W power supply with a 400w power supply, does that
automatically mean the electrical bill will be increased by 25%?

No.