How much power will I be wasting?

[Jim Bancroft]

I'm not a big gamer, but I have the choice of getting either a 550w or 450w PSU. Each is an 80 Plus, the 550w a Bronze. Believe the 450w is as well, almost certain.

Bigger is better but if I'm not using it to the maximum extent much of the time am I simply wasting power with the bigger unit? The 450w should work for my needs but if it's not much more expensive to run I'd prefer the 550w. Any rough idea how much more it'll cost per month in electricity?

I don't have the 12v numbers in front of me at the moment so apologies there. Just looking for a ballpark guess. Each unit is a solid name brand. Thanks!

 

[lehtv]

Can you post the exact model of each PSU please? What parts are in the PC that the PSU is supposed to power?

It's impossible to say, without knowing answers to these questions, which unit will be more efficient. What is certain, however, that the difference is so small that it's not worth paying extra for the more efficient of the two, other things being equal. E.g. typically, buying a Gold rated (90% efficient) unit over a Bronze rated (85% efficient) one can lower your electricity bill by perhaps $2 to $3 a year with a moderately power hungry and actively used gaming PC.

Also, are they your only options - where is it that you're buying from? Because the best way to save money on a PSU is to buy the unit that strikes the best balance between reliability and initial cost.

 

[MongGrel]

Recommendations based on vague information and being accurate is impossible more or less.

 

[MongGrel]

For a rebuild on one I purchased one of these recently, but this Main has a Delta 850 in it.

http://www.newegg.com/Product/Produc...82E16817371071

Everyone can go from there.

 

[Jim Bancroft]

Sure, I can give more info. The choices are these:

http://www.newegg.com/Product/Produc...82E16817139026
http://www.tigerdirect.com/applicati...449&CatId=5431

As for use, it'll be a typical PC more or less-- mobo/CPU, SSD boot drive, data drive (1 TB+), probably a Radeon R7 260x graphics card. The cx430 (which I already have) should be fine for that but if I wanted a better card I think it might struggle, which is why the XFX (Seasonic) is in the running.

But assuming the above configuration about how much extra $$ in electricity per year will the XFX be?

 

[MongGrel]

Personally I've never used either one but have seen a lot of people having problems with Corsairs CX series lately in forums.

The one I listed it Seasonic built, personally I'd go there or just get a Seasonic unit IMHO.

Getting cheap on you're PSU a bad thing I have no idea about power draw numbers on yearly cost other than a Gold will do it better to be honest or should.

I just don't like having a PSU that might be a unreliable to the other things I put into systems myself, as it controls the system more or less powerwise, ya know.

 

[lehtv]

Since you already have the CX430, keep using it. It will handle your system perfectly.

Upgrade the unit along with that new video card that CX430 won't handle, or if you happen to come across some sick deal on a high quality unit that you just can't let go.

I would not expect any noticeable difference in electricity costs. Firstly, I can't find any reviews of the CX430 to verify how its efficiency really behaves, so I have to trust the 80+ Bronze certification and assume it will be minimum 82% at 20% load [relative to rated wattage], 85% at 50% load, and 82% at 100% load. Efficiency below 20% load is not tested, and typically it will be significantly lower, perhaps 75% at 10% load.

Now, let's assume the CX430 and the XFX 550W behave the same, both being 80+ Bronze units. For your PC, the CX430 is the more balanced unit because it will dip below 20% load slightly less often, and will probably keep closer to the optimal 50% slightly more often. Let's say, when your PC is idling, XFX 550W is at 75% efficiency, while CX430 is at 76% efficiency, on average; and when you're gaming, CX430 is at the optimal 85% efficiency, while XFX 550W is approaching it at 84% efficiency, on average. Personally I think this is rather generous, but let's go with it anyway, and grant the CX430 that 1% efficiency advantage.

With that assumption, let's calculate how much $ you will save with the CX430. More assumptions: (1) your electricity costs $0.15 per kW, (2) in the average day of the year, your PC is idle for 2 hours at 60 watts and you play games on it for 3 hours at 200 watts.

The amount of power drawn by XFX 550W per year:
(2*60W/0.75 + 3*200W/0.84) * 365 days = 319 kW

The amount of power drawn by CX430 per year:
(2*60W/0.76 + 3*200W/0.85) * 365 days = 315 kW

With the CX 430 you save 4 kW per year in this example: 4 kW * $0.15 = $0.60. And again, I think this is a bit generous. Obviously, if you use your PC more than you do in this example, or if your electricity costs a lot more, then you would see bigger savings. But no matter what, you will never ever get back the money you spent on the XFX 550W.

 

[Jim Bancroft]

Since you already have the CX430, keep using it. It will handle your system perfectly.

Upgrade the unit along with that new video card that CX430 won't handle, or if you happen to come across some sick deal on a high quality unit that you just can't let go.

I would not expect any noticeable difference in electricity costs.

Obviously, if you use your PC more than you do in this example, or if your electricity costs a lot more, then you would see bigger savings. But no matter what, you will never ever get back the money you spent on the XFX 550W.

Thanks for the fantastic analysis. :thumbsup: