When you buy a PSU, you must buy twice as much as you need!!

Did someone hear such kinds of advice:

Quote:

"You should always get a [power] supply that supports about twice the load (on each given rail), in amperes, because that is how you better assure longevity, cool operation, quiet operation, max electrical efficiency (to save on electric bills), lowest ripple and noise current, and so on."

Twice? And also for each rail?

The statement looks strong. If my system needs 300W (3.3 & 5V: 40W; +12V: 240W), I must AT LEAST get 600W (3.3 & 5V: 80W; +12V: 480W) PSU to be safe. o_O It sounds like it's meant to be the only a minimum requirement.

Regarding the "double requirement" it said:

Quote:

Twice is the value I have gotten from lots of reading and communication in forums with people that help test and design power supplies.

From the sound of it, the "double requirement" is not some general advice. It has some science or research to support it. Yet I couldn't find one of them.

What do you think?

as far as getting double the wattage you would need as a must ... i completely disagree with that statement ...

as far as longevity ... this sounds possible ... look at it from a cars engine point of view ... if you are redlining your engine for months or years ... no it wont last as long as a car who never got over 2K rpms .... so i can see how that statement would somewhat have some validity to it... buuuuuut who knows ....

any 6-700W PSU will run every avg users comptuer out there ... heck it will run most every comp out there ...

unless you have like 10 HDs quad SLI 15 120mm fans .... and just crazy stuff like that ... you will be fine

EXTREMEoverclocker wrote:

as far as getting double the wattage you would need as a must ... i completely disagree with that statement ... as far as longevity ... this sounds possible ... look at it from a cars engine point of view ... if you are redlining your engine for months or years ... no it wont last as long as a car who never got over 2K rpms .... so i can see how that statement would somewhat have some validity to it... buuuuuut who knows ....

If it's the case, I believe the author is suggesting this:
100% load => much shorter life.
75% load => shorter life.
50% load => normal life.

This is my ideas. Feel free to comment.
I agree overstressing is bad. But it may not matter much between 50-80% load. They may have more or less the same impact.

Also too less work doesn't always mean better.

One's car used rarely VS my car used (nearly) daily -- that guy car happens to malfunction and break down much faster than mine.

I think some workload for the component is actually healthier.

Quote:

any 6-700W PSU will run every avg users comptuer out there ... heck it will run most every comp out there ... unless you have like 10 HDs quad SLI 15 120mm fans .... and just crazy stuff like that ... you will be fine

The only reason for a by far higher watt PSU is to prevent sudden spike of watt usage.

But I doubt it.

1) Manufacturer may take this into account and write the max watt required (including spikes)

2) I wonder if PSU may have measures to prevent shutdown due to such spikes.

3) I know motherboard will try not to load everything at once. So they load one by one. Of course all this happens for a second or so. I don't know if it's a standard feature for all modern boards.

The reasons behind this advice seems baloney.

However I think there are some other reasons which justify "much higher than needed" (still not unnecessarily double though!) -- Leaving room for future expansion.

When I pick a new PSU, my choice is narrowed down into 2:
A) buy a more powerful PSU (eg 500-700W) to serve me 5-7 years. It should still be able to serve me after 3 years I upgraded most components. The power consumption can be lower or higher but I assume the worse case.
B) buy a PSU which is just what I want (eg 300-400W). Of course some headroom has been included. Then upgrade PSU again after 3-4 years.

These factors affect my choice:
- price
- usefulness of adapter (it can help my PSU to be more future-resistant)
- degree of aging (how much percentage of power is reduced after 5-7 years)
- average lifespan of PSU

I only upgrade once every 3-4 years. At that time I upgrade I find out I always need throw all components away except "HDD / FDD / DVDRW" and maybe "PSU".

Which choices should I pick?
What do you think?

Well it's good to leave headroom if you plan on upgrading later on. 2x I think is overkill.

Best to use a PSU that will take a 60% load I would think if one does not plan on upgrading for a long time. It would be even better if you use a 80PLUS certified unit because there is little waste converting AC to DC.

Don't just look at the wattage though. Lots of PSUs claim a wattage but some blow (explode in some cases) before they ever reach their claimed capacity. Quality is always king.

Quote:

"You should always get a [power] supply that supports about twice the load (on each given rail), in amperes

That's good advice I'd say. Equipment uses amps based on it's workload.