When you actually do the math regarding efficiency you discover savings are normally fairly minor. In most cases you will have a hard time breaking even by picking an 80plus Gold PSU over a Bronze.
That's not to say you should avoid more expensive Gold or Platinum PSUs. They will make a difference in heat generated, and most importantly global power usage.
Take my current load: 120.9W at the wall. My PSU is a Seasonic X650, which is about 90% efficient at that load. So, I can calculate my actual DC draw to be 108W.
If I was using a Platinum Seasonic 1250W, my efficiency at that load would be about 85%, or 124W.
4W difference, despite the PSU being double the rating.
Your new CM PSU has a fairly flat efficiency curve according to Kitguru
http://www.kitguru.net/components/po...pply-review/5/
But they didn't test at a lower load that most modern machines will idle at.
This Greek site has the numbers you need
Coolermaster GX650W Bronze review
Now, an IT pro does need to know about temps vs. efficiency and might have to worry about that 4W difference if it was multiplied by a large number of users.
I thought I would address the question specifically as it comes up a lot and might help others as well.
@proximon, First thank you for the kitguru link and comments.
I knew about the lab.gr and it was one of the first review with the one
Here i readed about this power-supply.
I know it is a basic power-supply but quite well rated as it is also a second version, improved from Cooler Master for that GX series.
Now for those around buying a new power supply, efficiency from 82% to 92% makes a huge difference in Kw/year.
Let's say for a computer working 8 hours a day, 24/7, 365 days a year, makes around:
2920 hours working computer/year
Gx650w 80+Bronze low load results:
at
107,50 DC/AC (Watts), efficiency
82,85%, gives a PF/AC (Volts)
0.837/
232,6V.
Let's say the price i have to pay is around
0,10euro/$ Kw/h.
0.837 x 2920 = 2444,04 Kw/year
2444,04 x 0,10$/euro = 244,40$/euro to pay per year.
If i think about an 92,85% efficiency and make the same math about the cost for the results given, it will a difference of 24,40$/euro per year.
Then i will have to pay 220$/euro per year. Therefore, 2,03$/euro per month less to pay.
With those results,
it'll start to be interesting for me, only after two years, and if i decide to upgrade/new buy a power-supply 80+ Bronze to a 80+ Platinum or Gold.
Of course i'll have to wait at least 2 years to have my money back for the price i paid for an upgrade/new buy!!!:)
Because of so many crisis all around the world, prices are increasing next month for electricity to pay/month.
Gas was last month but my computer ain't Gas working!
The price of the power-supply actually doesn't fluctuate that much, then i'll be temporarily a winner!!!