Power supply wattage?

[0nRay]

Hi guys, I'm new to the forum but let me cut to the chase. I have a Kill- A-Watt and it says my system is drawing 280 watts from the wall running prime95 and furmark at stock speeds. My question is does this mean that technically I could get away with a 300W power supply? Or am I just being a n00b? I tried searching all major forum inc you guys but have come up dry so please don't flame me if this has been asked before. I'm just looking for a straight answer. My specs are as follows (ALL SPEEDS, TIMINGS, VOLTAGES ETC ARE STOCK ATM).

Thank you!

Phenom II 955be 3.3GHZ 1.35V C3 stepping

Asus sabertooth 990fx

AMD HD 6870

WD caviar black 1TB

8 noctua NF-F12 pwm fans

1 optical drive

1 tv tunner card

Xonar essence STX

 

[Chairman Ray]

You should get ~400W. A good rule is to stay below 80% capacity on PSUs.

 

[tiny voices]

Only buy from a reputable brand. (antec, xfx, corsair, seasonic)

Get 500w.

 

[MauveCloud]

Recommended wattage for that build via eXtreme Power Supply Calculator Pro v2.5 is 465 W with 31.1 amps on the +12V rail, so I wouldn't rely on being able to use a 300W psu.

 

[0nRay]

I see I forgot to mention that my PSU is an HX750. I would never gamble loosing all my hardware over a **** PSU, I just wanted to know if it was technically possible.

 

[0nRay]

So my question stands, Is it technically possible?

 

[tiny voices]

No, its not. under load, the GPU would suck too much power.

 

[Goodeggray]

I reason you want headroon in you psu is when psu start maxing out efficiency falls quickly. when efficiency less current is produced and more heat is putout. As temps increase efficiency drops even more. Leading to a burn out psu. I you know your system draws 280 watts max. Look for a psu with a output of 500 to 600 watts. Psus are most efficient running at half power, but you need to get a high quality psu too. There are no standards use in rating psu. Take a good psu vender like Corsair they have more than one 750 watt psu,but they are not equal. The cheaper one are rated at a cooler ambient temp but the top of the line psu are rated at a stated 50C. A psu can lose a lot of output as ambient temp rise. As much as 40%.

 

[0nRay]

Best answer selected by 0nRay.

 

[0nRay]

I reason you want headroon in you psu is when psu start maxing out efficiency falls quickly. when efficiency less current is produced and more heat is putout. As temps increase efficiency drops even more. Leading to a burn out psu. I you know your system draws 280 watts max. Look for a psu with a output of 500 to 600 watts. Psus are most efficient running at half power, but you need to get a high quality psu too. There are no standards use in rating psu. Take a good psu vender like Corsair they have more than one 750 watt psu,but they are not equal. The cheaper one are rated at a cooler ambient temp but the top of the line psu are rated at a stated 50C. A psu can lose a lot of output as ambient temp rise. As much as 40%.

That make absolute sense! I didn't even think about efficiency, good thing I have my hx750.