Using my old 1200w PSU on a 400w system.

[VelocitySpeed]

Is that safe? or even a good idea? and would it use up more electricity since im going to only utilize 400 watts? i have an old 1200 watt cooler master PSU that i bought last year to mine LTC and it's just sitting here.. So i figured i'd just use it on my next gaming rig. It will be my first time assembling my own rig so im not knowledgeable enough about PSU stuff. Thanks for the inputs!

[ForsakenLive]

Yes it's perfectly fine.

[Archangel1994]

The wattage only indicates what it CAN deliver, not what it WILL deliver so it's 100% fine to use an overkill PSU.

[connorpiper]

It might run at a lower efficiency. But not draw more power.

[Interfectorem]

Yes it's safe. It's a good idea if you just have it laying around. A PSU only pulls however many watts from the wall the system needs, not taking in account the PSU's efficiency,

[Izaya Orihara]

It might run at a lower efficiency. But not draw more power.

That is exactly what it frikken means. Lower efficieny of the PSU = Higher powerdraw from the wall. 

 

You probably mean that it will not draw 1200 Watts which is true but it will draw more power than a PSU that has 800 Watts and the same 80+ rating would as PSUs generally hit their peak efficeny at 50%. 

[connorpiper]

That is exactly what it frikken means. Lower efficieny of the PSU = Higher powerdraw from the wall. 

 

You probably mean that it will not draw 1200 Watts which is true but it will draw more power than a PSU that has 800 Watts and the same 80+ rating would as PSUs generally hit their peak efficeny at 50%. 

 

I know what efficiency is. (I have to do calculations every day for engineering)

I meant that in general, it would not draw 1200W from the wall, just what the computer needs and what is needed to combat the friction/resistance of the components and wires. 

[VelocitySpeed]

Okay.. i've purchased all the other components and decided to use my old 1200 watt PSU. Thanks guys! good to confirm that my electric bill would not increase because of the PSU's enourmous capacity =)