# Thread: How to Calculate System Wattage part 2

1. ## How to Calculate System Wattage part 2

Well my Energy meter can today, its a maplin meter (about £25 instore - £15 on Ebay), Wattage draw of my PC is lower than expected. See My System for general Specs

Booted up & Idle - 100w
Running Bioshock - 180-200w
3dMark06 - 175-200w

right now as typing its 105-125w

Can someone help and provide some suggestions of what to run to get overall component usage up so I can try and get some idea what the max wattage usage of my system is?

Currently looks like plenty of spare capacity for an extra HDD with my stock 350w PSU.

2. ## Re: How to Calculate System Wattage part 2

Depends on a few things

1) Amperage of your pSU on 12v

2) How efficient it is

3) Whether its a cheap chinese PSU and they just lied about the wattage

3. ## Re: How to Calculate System Wattage part 2

Opened the Box...

DC output 350w

+12VA -/ 12A Max
+12VB -/ 18A Max

"The maximum continuous combined output Power (12VA & 12VB) is 300W"

QUESTION - This is 25Amps on the 12v rail, yes? Is this enough?

QUESTION - Should I measure real Power or Apparent power when monitoring the Machine, I'm betting real but want to be double sure.

4. ## Re: How to Calculate System Wattage part 2

Sounds about right, for power consumption, amazing how many people massively over estimate there PSU requirements.

If it's powering your pc fine then I'd not be to worried about it.

The quality of the PSU would be my main worry, could be that while it works now it will not in the future.

Make and model tend to be the important factors here, Looking for an Underwriters Laboratories E number, put it into here and see what comes up.

Weight of a PSU can be a give away as to quality but not always.

PS are you overclocking your CPU?

5. ## Re: How to Calculate System Wattage part 2

I posted recently that my 450 tagan was happily powering an e6600@3.4Ghz, an overclocked 8800gtx and 6 SATA drives, still seems to be fine.....doubt I'll ever need a more powerful one unless I get multiple graphics cards....even then, how much more would I need!? A 650 maybe?

Save money, buy a decent lower wattage psu.

6. ## Re: How to Calculate System Wattage part 2

Originally Posted by Maccer101
QUESTION - Should I measure real Power or Apparent power when monitoring the Machine, I'm betting real but want to be double sure.
If you're measuring before it enters the PSU, its still AC, so measure Real Power.
If you're measuring post-rectification, then its DC so it'll just be Power.

7. ## Re: How to Calculate System Wattage part 2

No overclocking, its a Dell so BIOS is locked down for that, graphics card is factory OC'd no more room there either.

Measuring at the plug so Real Power it is thanks. Was expecting to see around 300w when playing a game was quite happy to see only a max of 200w

Pob225 Will have a look at that link

BTW, I notice alot of people just leave their PCs on, this is 100+watts 24/7! that must cost &#163;100-150 a year per PC, when my PC is sleeping is using 5 watts.

8. ## Re: How to Calculate System Wattage part 2

If your system have lots of hdds (4 or more), what you should really look is about 1~10 second after you push the power button, that usually shows the maximum power your system is going to draw. When my system had 10 drives, starting up draws 230W then drop down to 115W when all the hdds are on.

At 9p/kWh, you're looking at about 80 quids a year. And if a more power efficienct PSU cost 40 quids and save you 10 quids a year, it will pay itself back in 4 years, by the end of the 4 years you probably already swapped another PSU.

Well, thats of course assuming the electricity price won't triple in 4 years.