Whats the difference between standard efficiency and 89% efficiency psu

[arvinraj]

Hi, may i know what's the difference between the standard efficiency PSU and the 89% high efficiency PSU for the SFF model of HP Compaq 6000 Pro? Will it be worth upgrading from the standard one to the high efficiency?

Will there be any difference between the two in terms of max continuous power draw of the load?

If they are worth the upgrade, where can I buy them?

[fmyhr]

A quick eBay search for hp 600 pro sff power supply turns up quite a few choices. Most listings include pictures that show either "Standard Efficiency" or "High Efficiency" on the power supply label. Cost for a used, working power supply is about $20 including shipping. I don't know specifically what the efficiency of the "Standard Efficiency" PSU is, it could be as low as 65%. If the difference between the standard and high efficiency models is 20% and your power draw is 50W, then you'll save 10W if you upgrade. I'd suggest getting a Kill A Watt if you don't already have one and measuring the wall power draw yourself, before and after. (The Kill A Watt is incredibly handy around the house if you care about electric power usage.)

[arvinraj]

Thank you for the reply. Does this mean that both outputs a constant 240W max while the one with the higher efficiency will draw less wattage (nearer to ~269W)  from the mains socket?

[fmyhr]

Yes, 240W is the maximum either is rated to supply*. And when supplying 240W, a 90% efficient PSU will draw 240 / .90 = 267W from the wall, whereas a 65% efficient PSU would draw 240 / .65 = 369W. Your computer will pretty much always use much less power than the rated 240W (otherwise, the power supply would be too small.) Usually power supplies achieve peak efficiency around 50% of max rated load: 120W for these supplies. To take advantage of this peak efficiency, usually a computer power supply is sized so that it can supply about twice the power the computer is expected to use. So probably HP expects your computer to use about 120W max. In fact your computer probably draws significantly less than 120W most of the time. I would guess more like 50W, but it depends on what you have installed, and how busy you keep the CPU, GPU, disks, etc.

* The 240W total is split among several voltages: 12V, 5V, 3.3V. Each of them has their individual power limit, and together these limits add to 240W. If you're building your own system you should consider each of these limits separately (with 12V usually being the most important). Fortunately HP has done that work, and used a PSU with appropriate ratings for your computer.