need to downgrade my psu's.

Schizo · 28 Nov 2009 at 22:21

im cutting down on the heat/power and noise in my pc.

i have got rid of 2x asus radeon 4850's and got a 5770 (nice move tbh).

im selling my xspc watercooling set up and getting a h50.

and i want to get rid of my antec p190 power supply's (total of 1200 watts)

what psu will i need when i get rid of my 2 psu's ?

my system consists of a-
q6600
1 hard drive
1 dvd drive
1 5770 (might be 2 soon)
card reader
fan controller
7 fans on low
8gb ram

will a 600 watt do me ?

OpenToSuggestions · 28 Nov 2009 at 22:22

Even with 2 5770's a 500w would be more than fine.

I would probs get a 600w just so you have some upgrade room in the future.

Destination · 28 Nov 2009 at 23:33

You are aware your PSUs only draw the wattage they actually require, they don't just generate heat from excess electricity for the fun of it?

You should get a power meter and check what wattage you use, then chose a PSU approx *1.25 this wattage, so the PSU you use will be in its optimum efficiency phase.

- additionally, is your system overclocked and do you really need that fan controller?

CBJ · 28 Nov 2009 at 23:33

Why are you getting rid of your power supplies? They only draw what your system uses regardless of their maximum power output. Obviously there's some loss through inefficiency too, but I think I'm right in saying that you generally get better efficiency from a power supply that is operating at well below its maximum rated output. If the power supplies are noisy then I can understand the logic, but downgrading ones with a lower maximum rated output isn't going to save energy or generate less heat.

Mattus · 29 Nov 2009 at 02:51

CBJ said:
Why are you getting rid of your power supplies? They only draw what your system uses regardless of their maximum power output. Obviously there's some loss through inefficiency too, but I think I'm right in saying that you generally get better efficiency from a power supply that is operating at well below its maximum rated output.

To an extent, yeah. A PSU is least efficient when it's running right on its limit, but it's also quite inefficient when the load is very small. If his PSUs can supply 1200 watts but his system only draws 200, for example, the load would be too small to get the best efficiency from the PSU. In that case, having a single less powerful PSU would be a bit more efficient because it's more suited to smaller loads.

Schizo · 29 Nov 2009 at 07:03

but surly both psu's creates a lot of heat ?

this is my point in getting rid of stuff that create heat and 2 psu's is one of them.

EsaT · 29 Nov 2009 at 10:55

Peak draw of those parts isn't much above 200W so even under full load efficiency of PSUs is probably below 80% and at desktop 70% shouldn't be far from the mark.
With this low load already "idle" power consumption of two separate PSUs themselves is going to degrade efficiency.

Corsair VX450 would be good choise, CX400, while being more fitting wattage seems to have cheaper less efficient design.
Also newer Enermaxes of that rating would be good ones.

Then there's Seasonic's new X-650 which probably exceeds those in efficiency even at lowest idle load because of different new design... and in that bottom chamber might run passively nearly always because of so little heat produced. (SPRC tested it in 23C ambient and with 110VAC fan started at 340W load)