Someone explain PSU's and Electricity Bills!

Andybtsn · 7 Dec 2013 at 13:04

Hi guys,

I have a pretty hefty rig that consists of crossfire 7970's, 4770k and a 1000w PSU (Seasonic 1000w '80 Plus Platinum' Modular Power Supply)

Now I'm not gaming on this rig much anymore but I do have the PC on of average 6 hours a day. I'm a bit worried of the electricity bill because of this and I'm pretty much only using it for web browsing, iTunes and Football Manager!

Will the PSU resort to a lower watt rate when not being use to full potential? I don't really want to downgrade but we've moved into a house much more expensive to run than the last so if I can save some pennies I will try to.

First thought was going from a crossfire setup to one GPU and also downgrading the PSU?

Let me know your thoughts.

Andy

RJC · 7 Dec 2013 at 13:10

The PSU will only pull whats needed.

Your system I think would pull around 600w odd at full load.

Invest in one of these:

http://www.overclockers.co.uk/showproduct.php?prodid=NW-003-EN&groupid=702&catid=55

Idle - probably around 100w~

My system with a overcloced i7 4700k and the Asus Top I think got around 330w ~

OLDPHART · 7 Dec 2013 at 13:48

Imao, he spends all that money on a rig and worries about how much electricity it will use and guess what he's a > Yorkshireman.

krnsniper · 7 Dec 2013 at 15:46

If you want to save some energy that is being wasted then I suggest you pull out one of the 7970's as that pulls power even when idle. As for the PSU, there's no need to downgrade as it will only supply how much is being demanded by the rest of the system.

Orionaut · 7 Dec 2013 at 17:14

krnsniper said:
If you want to save some energy that is being wasted then I suggest you pull out one of the 7970's as that pulls power even when idle. As for the PSU, there's no need to downgrade as it will only supply how much is being demanded by the rest of the system.

However the efficiency with which the PSU does this varies across the load range.

Typically PSU's operate at their maximum efficiency at somewhere around 60% of full load, below that they consume more power/watt delivered and above that they do also! (You will need the check the power curve of individual PSU's for precise figures)

For a PC left on all the time, you will get the cheapest running if you match the power required to the max efficiency point on the PSU.

Typically this means using a significantly overrated PSU (On paper). The other advantage of doing so is that the PSU will be less stressed, run cooler and lilky last longer.

Confused Stu · 7 Dec 2013 at 20:46

krnsniper said:
If you want to save some energy that is being wasted then I suggest you pull out one of the 7970's as that pulls power even when idle..

The point of ZeroCore is that the GPU essentially powers off when it's not in use. This means in a crossfire rig, the second GPu switches off and uses no power when you're not playing a game. Obviously, this is disabled if you disable ULPS.

For the pedants among the audience (that includes me), the GPU doesn't completely switch off. It maintains enough of the GPU to allow the PC to recognise something that's turned off is attached, but nothing more. I've not seen figures for how much power a GPU uses in zerocore mode, but it's near as dammit zero.

Hyburnate · 7 Dec 2013 at 21:15

Orionaut said:
snip.

But the money you'll save from going for a platinum is no more than MAX £10 a year which is not really worth it, I doubt it's even close to that.

OLDPHART · 7 Dec 2013 at 23:02

Hi again, sorry but couldn't resist it but it did make me laugh.

Often though about this my self as bills get higher, would a laptop not do for browsing and Football Manger plus you might already have one?

Orionaut · 7 Dec 2013 at 23:38

Hyburnate said:
But the money you'll save from going for a platinum is no more than MAX £10 a year which is not really worth it, I doubt it's even close to that.

I think you misunderstand.

Doesn't have to be a Platinum as such.

More a 1000W PSU for a 600W rig IYSWIM (Or whatever)

And there are other advantages too.

(And, more to the point of the OP. Getting a smaller PSU will almost certainly make things worse!)

EdgeDs · 8 Dec 2013 at 05:37

Do you need crossfire for a football sim?

oceaness · 8 Dec 2013 at 10:16

Orionaut said:
Typically PSU's operate at their maximum efficiency at somewhere around 60% of full load, below that they consume more power/watt delivered and above that they do also! (You will need the check the power curve of individual PSU's for precise figures)

A Platinum PSU can only vary by 4% efficiency between 20% and 100% load. So aiming for around the 50% load mark is a bit of a waste of money, it wont really save you anything compared to the vastly increased cost of a unit twice as powerful as you need.

The difficulty in Andy's situation often comes with the idle load when using a gaming rig for menial everyday tasks.

80+ PSU's are pretty efficient above 20% load. Where they often struggle is below 20%, efficiency here can drop off pretty sharply for some units. However Andy's PSU should manage about 84% efficiency right down to 10% load and I would guess the rig would idle around the 16% mark.

A PSU is rated for a certain amount of wattage, it can provide anything up to this. It does this at a particular efficiency.

At 160W load if we assume a minimum of 84% efficiency it'll be using 190W at the wall. This would equate to £4.35 a month at 6 hours a day and a unit rate of 12.678 p per kWh.

As mentioned if you already have a laptop, it'd be considerably more energy efficient for web browsing, I'd plug a decent keyboard and mouse in if using it for 6 hours.

One other thing you can do is set either your rig or a laptop, if you chose to use one, to sleep after 10 minutes of inactivity if you often walk away from it. This will also benefit your energy usage because it will put the screen into standby too.