Electronics > Projects, Designs, and Technical Stuff

switching-PSUs: why can't you usually exceed the 50% of declared power?

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wraper:

--- Quote from: engrguy42 on May 24, 2020, 01:52:13 pm ---
--- Quote from: wraper on May 24, 2020, 01:30:00 pm ---
--- Quote from: engrguy42 on May 24, 2020, 01:20:29 pm ---Again, do you have ACTUAL numbers to support this, or is it just vague generalizations based on personal belief?

--- End quote ---
Say ((15W (efficiency difference) * 8h * 261 days + 3W * 24h (standby PSU efficiency) * 365 d) * $0.20 kWH = $11.5

--- End quote ---

So you're running your computer at full power for 8 hrs/day, 365 days/year?

--- End quote ---
Check the numbers again, there are 261 days. 365 for standby part. If it was my computer, difference would be much higher since I run it about 12-14 hours a day, and especially if I ran it "at full power" since it's high end PC with high-end GPU.

engrguy42:
My suggestion for those who really want to understand computer power supply and GPU power usage...

Get a cheap kWH monitoring device (like a KillAWatt), and plug your computer into it. It will tell you the ACTUAL kWH usage of your entire computer (including GPU) over time. You can then calculate the difference if it had a different efficiency power supply, and calculate a more realistic value of cost savings.

GPU's and other computer components don't use a fixed amount of power during the day, nor do they operated at maximum ratings all day. It varies. And in some/many cases they never reach their rated power specification, depending on the software they're running.

You may be surprised that the cost savings you thought you were getting just aren't there. 

coppice:

--- Quote from: engrguy42 on May 24, 2020, 02:06:32 pm ---My suggestion for those who really want to understand computer power supply and GPU power usage...

Get a cheap kWH monitoring device (like a KillAWatt), and plug your computer into it. It will tell you the ACTUAL kWH usage of your entire computer (including GPU) over time. You can then calculate the difference if it had a different efficiency power supply, and calculate a more realistic value of cost savings.

GPU's and other computer components don't use a fixed amount of power during the day, nor do they operated at maximum ratings all day. It varies. And in some/many cases they never reach their rated power specification, depending on the software they're running.

You may be surprised that the cost savings you thought you were getting just aren't there.

--- End quote ---
I'd recommend any serious engineer to get a KillAWatt or two, and monitor some of the things around their home. Anyone competent knows the approximate power consumption of most of the stuff around the house, but usage patterns determine the total energy consumed. Those patterns are not always obvious until you start making some measurements. It can be quite revealing.

PKTKS:

--- Quote from: engrguy42 on May 24, 2020, 02:06:32 pm ---(..)
You may be surprised that the cost savings you thought you were getting just aren't there.

--- End quote ---

Very true indeed.

Add to the list of costs a REQUIRED TRUE SINE INVERTER
for those setups using PFC based sensitive loads.

A couple of months a guy called me asking my opinion
about someone trying to sell him a "PC" above the barrel...
with multi-core i9 power latest gen GPU and awesome 1000W PSU
Which included a TRUE SINE INVERTER NoBreak of 2KW

Just to run MS word on a desktop dozen times a day.
The folk argument is that MS Win GUI now requires a GPU
for proper display office and an i9 multi-core CPU with
liquid cooling is required to handle ANTI VIRUS stuff

Of course the gain margin of the folk was  considerable as well

I gave him my opinion which is absolute unprintable here...

Paul

Monkeh:

--- Quote from: engrguy42 on May 24, 2020, 02:06:32 pm ---You may be surprised that the cost savings you thought you were getting just aren't there.

--- End quote ---

The figures I measured were at idle of a configured system. Consumption simply will not have been lower at any time. I'm sorry this doesn't support your argument, but that's the problem with biases.

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