Do energy efficient PSUs pay for themselves?

[888qqq]

Do energy saving PSUs like Corsair, Seasonic, and Silverstone pay for themselves in energy savings? I know there are several factors like the amount the computer is used, how the computer is used and cost of electricity in the area, but in general are they worth the added cost? Thanks for any replies.

 

[F1shF4t]

Its more to do with realiability and quality. In that way they do pay for themselves since cheap generic POS can kill your hardware.

Most of the psus (unless really crappy) are around 80% efficiency. Lets say 250 watts 24/7 for a year at 84% efficiency and 76% efficiency. Comes to 298 and 329watts AC power used respectively.

24 * 365 = 8760 hours in a year.
329 - 298 = 31 watts extra losses from cheap psu

0.031 * 8760 = 271.56 kWH wasted in losses

Here in Australia costs are around 17C per kWH.
271.56 * 0.17 = 46.17 Dollars


However most people won't keep their computers on 24/7 and power use will warry between load and idle and will depend on the hardware you have. Ofcourse the more power you use the higher the savings.

 

[Vertigo0176]

It's better to use a quality power supply, but it will never pay for itself because no mater how efficient it is, it will still cost money to use.

 

[Zap]

Generally speaking, they do not pay for themselves. Occasionally they can. For instance if someone was running an old 60%-efficient PSU drawing 400W from the wall in a 24/7 system and they pay really high kW/h rates then buying that $15 Enhance 80+ PSU from Geeks (deal from a month ago) would pay for itself in a few months.

Most people would probably already have upgraded/sold the replacement PSU after a few years before they realize any savings.

 

[Lunyone]

Well if you consider the parts that you may have to buy with a cheap and usually not efficient PSU. Yes even the efficient and quality built PSU's make an occasional bad unit, but the warranty and service offered usually pays for itself.

 

[Golgatha]

Originally posted by: Vertigo0176
It's better to use a quality power supply, but it will never pay for itself because no mater how efficient it is, it will still cost money to use.

I run Folding@Home 24/7/365 and will save roughly $25-30 per year (Missouri electricity is cheap at $0.08 per kWh and I calculated 8000 hours uptime) by switching power supplies. With a 5-year warranty, I'd say I'm looking at $125-$150 overall savings, which is basically the cost of the power supply when you figure in the amount I got from selling my old unit (Silencer 610w, running near max capacity, so the efficiency was near 80% vs 88% for the load on my new 910w Silencer).

To me it was a no-brainer to switch. I needed something that can handle my system and the efficiency will help offset the cost of the upgrade over the long haul. No to mention the 910w doesn't sound like a blow dryer

 

[cbn]

Originally posted by: 888qqq
Do energy saving PSUs like Corsair, Seasonic, and Silverstone pay for themselves in energy savings? I know there are several factors like the amount the computer is used, how the computer is used and cost of electricity in the area, but in general are they worth the added cost? Thanks for any replies.

If you live in California energy costs can approach 25 cents Killowatt hour (if a household goes over a specified amount)

So it depends on how much more the energy certified PSU costs comapred to one with lower efficiency.

Personally I am wauting for SSD prices to drop because really fast boot-ups might help a person make the decision to turn off their computer more ofter (while still being practical)

 

[HOOfan 1]

Originally posted by: Just learning


Personally I am wauting for SSD prices to drop because really fast boot-ups might help a person make the decision to turn off their computer more ofter (while still being practical)

of course SSDs also use less power than a spinning hard drive

 

[Zap]

Originally posted by: Just learning
Personally I am wauting for SSD prices to drop because really fast boot-ups might help a person make the decision to turn off their computer more ofter (while still being practical)

People should look into sleep/hibernation. I use hibernation on my notebooks and boot times (especially on the 1GB RAM netbook) are really quick compared to a normal boot-up.

 

[Modelworks]

Is there any one agency verifying the efficiency of a PSU ? Or is it just each company doing their own testing ? Seems like a easy way to increase sales. Put the 80% efficiency label on the box knowing that most people will never test it.

 

[Zap]

Originally posted by: Modelworks
Is there any one agency verifying the efficiency of a PSU ?

http://www.80plus.org/

For a PSU to have that "80 PLUS" logo, it has to be certified by that organization.

There are a few things to know regarding certified and non-certified PSUs:

A power supply not certified "80 PLUS" does not mean it is not efficient. It just means the power supply did not pass one of the tests (there are three test points) or was never submitted for certification. Submitting a sample for certification costs money (AFAIK several thousand) which some companies may not want to invest in.

A power supply that is certified "80 PLUS" does not mean it has top-notch output characteristics. AFAIK the 80 PLUS organization just tests for efficiency and doesn't test for voltages (as long as not out of spec), ripple, etc.

80 PLUS does not test at really low outputs (below 20%) so people wanting to "future proof" by buying ginourmous wattage PSUs to run a low end system may be running at much lower efficiencies than the "80 PLUS" label would imply. (This is a generalization, not all PSUs are inefficient at really low output levels.)

Most power supplies have their highest efficiency at around half of their rated output, so plan your purchase accordingly.

Unless gaming all the time or doing something like Folding, most systems pretty much run at idle speeds most of the time. Figure out at what wattage your system spends most of its time and plan your purchase accordingly.

In a standard ATX chassis configuration the power supply will heat up during use and be less efficient due to "derating."

http://en.wikipedia.org/wiki/80_PLUS

For a given power supply, efficiency varies depending on how much power is being delivered. Supplies are typically most efficient at between half and three quarters load, much less efficient at low load, and somewhat less efficient at maximum load... Thus it is still important to select a supply with capacity appropriate to the device being powered.
...
The testing conditions may give an unrealistic expectation of efficiency for heavily loaded, high power (rated much larger than 300W) supplies. A heavily loaded power supply and the computer it is powering generate significant amounts of heat, which may raise the power supply temperature, which is likely to decrease its efficiency. Since power supplies are certified at room temperature, this effect is not taken into account.

80PLUS does not set efficiency targets for very low load. For instance, generation of standby power may still be relatively inefficient... Inefficiencies in generating standby power are magnified by the amount of time that computers spend turned off.

 

[cbn]

Originally posted by: Zap

Most power supplies have their highest efficiency at around half of their rated output, so plan your purchase accordingly.

Good point about maximizing the efficiency by not "oversizing" the power supply.

 

[Zap]

Originally posted by: Just learning

Originally posted by: Zap

Most power supplies have their highest efficiency at around half of their rated output, so plan your purchase accordingly.

Good point about maximizing the efficiency by not "oversizing" the power supply.

... OR undersizing it. There's a happy medium somewhere in there...

 

[elconejito]

A more efficient PSU should also decrease the wattage pulled from the wall right?

I currently have a coolmax 500w (I'm sure way less than 80% efficient) running my 24x7 media center. Kill-A-Watt says i'm pulling ~100w during idle and ~105-110w during use. I'm considering getting a smaller PSU that is at least 80+ certified. Specifically, I'm looking at the Seasonic 300w (ES or ET? I dunno) but the Antec Earthwatts 380w is at a real good price.

Considering the greater efficiency, this should drop my energy usage by a few watts at least right? If I can save maybe 5-10w then for me it's worth it. I'm looking for somebody (anybody) to tell me i'm on the right track or I'm crazy. I also plan on trying a few other things like maybe underclocking to save a few more watts.

 

[Zap]

Originally posted by: elconejito
I currently have a coolmax 500w (I'm sure way less than 80% efficient) running my 24x7 media center. Kill-A-Watt says i'm pulling ~100w during idle and ~105-110w during use. I'm considering getting a smaller PSU

If you want the best power savings, prepare to spend a bit more coin.

http://www.mini-box.com/Power-Supplies-Kits

AFAIK these are the most efficient PSUs for low wattage systems, and you should aim as low as possible on the rated power.

This example (see first chart) shows power draw for the same system using two different 80+ certified power supplies from Seasonic. One is a 400W unit while the second is a 300W unit. Note that there was anywhere from 3-6W difference in how much power was pulled from the wall outlet.

This example shows a PicoPSU compared to a Seasonic 330W that is 80+ certified. Take a look at the second chart for "IN-SYSTEM TEST." For the CPUBurn test the Seasonic 330 was drawing 80.0W while the 120W PicoPSU was drawing 72.6W.

 

[elconejito]

thanks for the links zap. That confirmed what I thought about a more efficient PSU dropping my wattage by at least a few.

I've heard of PicoPSUs before (on SPCR forums actually). I've never really considered them since they seem to mainly be used in really small applications. For example, if I just had one drive, one tuner in a small form factor case (at least thats my impression anyway). My media center, in a mid-tower, has 4 tuners (2x combo cards), 3 hard drives plus a DVD so right off the bat I'd worry about the number of connectors available. I'd also probably look at the 120W version which i hear is hard to come by. Have you used one? Or have some pics of them actually in a case? I'd be curious to see how the cable layout goes.

However, if I can get the wattage down into the 80s (I think i can) then I'd seriously look at the Pico 102w to shave off a few more watts. I feel more comfortable having that extra cushion.

 

[Zap]

Originally posted by: elconejito
I'd also probably look at the 120W version which i hear is hard to come by. Have you used one? Or have some pics of them actually in a case? I'd be curious to see how the cable layout goes.

However, if I can get the wattage down into the 80s (I think i can) then I'd seriously look at the Pico 102w to shave off a few more watts. I feel more comfortable having that extra cushion.

I actually have a picoPSU 120W sitting unused in my garage (no AC adapter though). Not sure it would be good for your purposes because IIRC it doesn't support four drives.

Perhaps you should look into the new picoPSU 150W model?

 

[elconejito]

Do you know offhand how many connectors it has? Looking on the site I can't tell how many connectors it has, unless I'm just being really obtuse.

After my last post I actually disconnected one of the drives to see a) how much power it would save and b) if I'd lose any performance. Answers were a) ~2-3w on average and b) so far so good. The 3rd drive was used just for timeshifting, keeping it separate from OS/apps on 1st drive and recordings on the 2nd. So now I've got os/apps/timeshifting on one drive and recordings on the other. I haven't run into a situation yet where the OS is doing something (A/V scan, transcode, whathaveyou) while watching TV. I suspect the drive (a new WD10EADS, replacing a WD2500KS that died a month ago) has enough bandwidth in the event it does.

 

[Zap]

Originally posted by: elconejito
Do you know offhand how many connectors it has?

The connectors have changed over time. I think mine didn't have the SATA connector but the new one does.

picoPSU connectors

150W
24 pin ATX
4 pin peripheral
SATA
4 pin +12v Aux

120W
20 pin ATX
4 pin peripheral
4 pin floppy
SATA

90W
20 pin ATX
4 pin peripheral
SATA
4 pin +12v Aux

One each of all listed connectors. You can download the PDF manual for more details (available on all product pages there).