Choose a PSU based on 50% load?

[gfair]

In reviewing the efficiency curves of power supplies from 20%-100% on the 80 Plus site, they all seem to peak around 50% of full load.

Here's an idea I'd like to put forth:

- PSUs seem optimal at around 50% of maximum power.

Why not determine typical power use for the primary purpose of your computer (e.g. gaming) and pick a PSU double that so your typical power use comes in at ~50% of the maximum of your PSU, ensuring you are hitting the highest optimal range of the PSU when using your computer?

 

[jsc]

That's what I do. I like to run my PSU's at 50% - 70% capacity. The problem lies with generating an accurate estimate of power comsumption. But because most PSU calculators online tend to be very conservative, just doubling their estimates tends to result in a highly overspecd power supply.

I am lucky. I have access to equipment to measure power use right at the motherboard power sockets.

 

[ainarssems]

70-85% at full load, 30-50% on idle.

 

[WR2]

+1 to ainarssems
Better suited to for the majority of PC owners.

 

[theAnimal]

The problem lies with generating an accurate estimate of power comsumption. But because most PSU calculators online tend to be very conservative, just doubling their estimates tends to result in a highly overspecd power supply.

The PSU calculator does not give you power consumption but recommended PSU wattage.

 

[JohnnyLucky]

+1 what theAnimal said.

A lot of the psu power calculator recommendations are overestimated because there are a lot of low budget, poor quality psu's of questionable value. On the other hand a lower wattage high quality psu can often produce better results.

One of the problems I've run into is trying to determine actual power draw under different conditions and with different components. It's not that easy to figure out. It's even more difficult when it comes to overclocked cpu's and video cards. It was only a few days ago that I accidently found a power consumption chart for specific brands, makes, and models of video cards.

Another problem is the entire concept of efficiency. What is the meaningful difference between certified bronze 80% efficiency and certified silver 87% efficiency? What does an increase of 7% efficiency mean for a computer user?

 

[ainarssems]

What is the meaningful difference between certified bronze 80% efficiency and certified silver 87% efficiency? What does an increase of 7% efficiency mean for a computer user?

That means lower electricity bill, lower heat from psu, lower psu fan rpms, less noise from psu. All by a very little margin, not noticable.

 

[theAnimal]

Another problem is the entire concept of efficiency. What is the meaningful difference between certified bronze 80% efficiency and certified silver 87% efficiency? What does an increase of 7% efficiency mean for a computer user?

It's actually only a 3% difference between bronze and silver ratings (82-85-82, 85-88-85).

 

[JohnnyLucky]

theAnimal - I got curious and did a little research. The trail led to 80plus.org. I discovered efficiency is a bit more complicated. There are 80 plus, 80 bronze, 80 silver, and 80 gold certifications for power supplies. The psu's are meant to be used together with pc's and servers that are Energy Star version 4.0 compliant.

Seasonic had the first 80 plus certified psu a couple of years ago. It was one of their 400 watt models. The current king of the hill is the OCZ Z1000 psu. It is 80 gold certified - average efficiency is 89.46% and peak efficiency at 50% load is 90.93%. It will be available sometimes this Spring in standard and modular versions and come with a 5 year warranty. Currently there are no technical reviews.

ainarssems - I found some facts and figures over at 80plus.org. If a person switched from a typical pc to one that was Energy Star 4.0 compliant and had a psu that was at least 80 plus certified then the energy savings in the USA would be about $14.00 per year. That's based on a national average cost of 9.5 cents per kilowatt hour of electricity. I'm guessing this might not apply to hardcore gamers into serious overclocking who build their own high end systems.

 

[theAnimal]

The highest efficiency according to 80Plus is Delta DPS 350W with 89.84 average and 91.36 at 50%.

 

[JohnnyLucky]

theAnimal - GEE! That Delta unit was just tested last week. Like the OCZ psu it doesn't appear to be available yet. No mention of it at the Delta web site and no press releases. Don't think it would do for most gamers and/or overclockers due to low wattage and amperage.

I wonder who else is going for the gold.

 

[JohnnyLucky]

wusy - Agreed. Recent THG article about video card power consumption and two other references I found also indicated a power draw of about 500 watts during a typical gaming session. Final figure depended on the number and type of video cards and extent of overclocking.

 

[theAnimal]

theAnimal - GEE! That Delta unit was just tested last week. Like the OCZ psu it doesn't appear to be available yet. No mention of it at the Delta web site and no press releases. Don't think it would do for most gamers and/or overclockers due to low wattage and amperage.

I wonder who else is going for the gold.

There are currently 31 Gold certified PSUs, but AFAIK none are yet available to purchase.

 

[JohnnyLucky]

theAnimal - I downloaded the entire list in MS Excel format. Then I reduced it to just the 80+ Silver and Gold certifications. As of today there are a grand total of 125 psu's. in those two categories. Next I'm going to try and determine which ones are currently available for sale and whether or not there are any technical reviews. It's going to take me a while to sort things out. It's probably not going to be as easy as it sounds.