Going from a 85% to a 90% effecient PSU worth it?

[videobruce]

How much actual wattage drop with a given PC going from a 85% efficient PS (rated at 600w for example) to a 90% efficient supply? IOW's when measuring the AC current at the wall, using a 600w rated supply as the example, how much less wattage could I expect? 5, 10, 15 watts?

Is the extra $$ worth it?

 

[Skullcrusher1.0]

600w @ 90% = 540w
600w @ 85% = 510w

 

[jacktesterson]

No - 80+ Bronze is the sweet point. I don't feel going higher is worth the premium unless you get it on sale.

Doesn't always work the same as above. My ZT 550w can do all 550w on the 12v rail (45a) yet is 80+ Bronze.

 

[lehtv]

600w @ 90% = 540w
600w @ 85% = 510w

Having a 600W unit doesn't mean you actually use 600W. So those numbers mean nothing unless you're stressing the power supply to its full capacity for long periods of time - which you should never do, really.

@ OP

For the average user it's not worth it with respect to the cost of electricity, unless you pay only marginally more for the higher efficiency unit. With a cost of electricity of 10c per kWh and a usage of 5h/day at an average of 200W (from the wall), you'd use 10c worth of power each day or $36.50 per year. Upgrading from a 85% efficient unit to 90% efficient one would save only $2 per year. If you assume the high efficiency unit is only $20 more expensive than what you'd get from selling the old unit - which is probably not going to happen - it would take a decade for that upgrade to pay itself back.

In special scenarios the higher efficiency becomes more viable. E.g. you want a unit that is silent even with your system at full load. Or you have much higher than average system load per day, e.g. 8h of video editing per day and rendering at night. Or your area has abnormally high cost of electricity.

 

[Nec_V20]

The wattage rating of the PSU is the maximum that it is rated to supply reliably.

The percentage relates to the amount of AC current the PSU has to draw in order to produce the DC output. This value translates directly to your wallet.

At 600 Watts output an 85% efficient PSU would have to draw 706 Watts from the wall. For a 90% efficient PSU it would have to draw 667 Watts.

The 90% PSU will be just over 5.5% cheaper to run than an 85% efficient PSU.

If you have your computer on 24/7 that will make a lot of difference in the price of running your PC and you would have to work out for yourself whether or not the higher price of the 90% efficient PSU will amortise itself for you in a reasonable time with regard to a cheaper 85% efficient one

 

[Skullcrusher1.0]

I thought higher power efficiency was like a guarantee that at least that percentage of electricity is not wasted. If you can get all 550W off OCZ ZT bronze then I am not understanding correctly I guess!

:\

http://www.plugloadsolutions.com/psu_reports/OCZ TECHNOLOGY_OCZ-ZT550W_ECOS 2681_550W__Report.pdf

 

[videobruce]

I clarified my OP. I was basing my question on a 600w rated supply, not a device that draws 600 watts at the outlet.
Say a PC draws 100 watts on average from the wall with a old 80 plus supply from before there were these ratings, what drop in current would moving up to a 85% or 90% efficient supply provide?

I wasn't just interested in the cost of electricity.

 

[videobruce]

At 600 Watts output an 85% efficient PSU would have to draw 706 Watts from the wall. For a 90% efficient PSU it would have to draw 667 Watts.

But, a 600 watt PC PSU does not draw 600 watts at 120 VAC.

 

[Skullcrusher1.0]

http://www.plugloadsolutions.com/psu_reports/CORSAIR_75-02018_600W_ECOS 3400_Report.pdf

vs.

http://www.plugloadsolutions.com/psu_reports/ATNG POWER_ATM-600series-P_ECOS 2835_600W_Report.pdf

 

[videobruce]

Thanks, but those only show output, not input. Both are rated at "10-5" amps input.

 

[Skullcrusher1.0]

input wattage is to left of output wattage at bottom

 

[videobruce]

But that is at the output voltage of 12vdc, not 120vac.

 

[Nec_V20]

http://www.plugloadsolutions.com/psu_reports/CORSAIR_75-02018_600W_ECOS%203400_Report.pdf

vs.

http://www.plugloadsolutions.com/psu_reports/ATNG POWER_ATM-600series-P_ECOS 2835_600W_Report.pdf

We have 230 Volts AC where I live, so that makes the same PSU about 1% more efficient than using it with 120 Volts AC.

Of course the other thing to remember is that the more efficient the PSU is the less heat it produces, so this could also translate to the longevity of the PSU.

The thing is to shop around. For instance I got two Corsair AX860's each was cheaper than I would have had to pay for either an AX750, AX760, AX760i or an AX850. Each one only cost slightly more than an HX850 (pennies of difference, not pounds).

I had actually had my eye on the Corsair TX750 originally and came across the offer of the AX860 by accident. Of course when I saw the difference in price was tolerable I decided to go for the AX860.