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How do I work out my PSUs efficiency?

M

m4rky

Junior Member
As per the threads title, How do I work out how efficient my PSU is?

Correct me if I am wrong, but efficiency is calculated as:

Load in DC required by system / Load in AC drawn from Power Socket.

I have a plug in power meter so I can get the Load Drawn from the power socket.

But how do I find out how much my system currently requires?
 
No A psu runs at its best efficiency when its carrying a 40 to 60 percent load. Thats why they always say when using a psu calculator to multiply by 2.
 
There might be a mis-understanding of what I am after.

While the PSU might might running at its most efficient at 40-60% load.
That doesn't mean that its an efficient PSU?

I am trying to work out if my old PSU is worth replacing with a newer one.

If my old PSU is only 70% power efficient then a newer one may be 85% efficient at the same system power requirements.

My HTPC and server are on 24hrs a day so over a year a better PSU may use less electricity.

But I don't know how efficient my old PSU is so I can compare.
 
Without some way of measuring the DC side, you don't.

The reviewers who calculate efficiency have devices that you plug the power supply into, then cords that go to the computer components and everything on the DC side gets measured by that device. Casual users like you and I don't have those devices, they cost more than an expensive power supply, so it would never make monetary sense to buy one.

If you give me:
- what you're seeing from the wall on your meter
- how much your electricity costs per kWh (mine is tiered, and we are in a tier where it's about 35 cents per kWh, while the initial tier is only 11.5 cents per kWh... big difference)
- Brand and model of your current PSU

Then I can calculate the rough savings you would see from a different PSU and you can look at whether the Return of Investment is worthwhile.
 
You cannot calculate psu efficiency directly without specialized equipment. The best you can do is compare different psus and see what the wall draw is to determine which is most efficient.
 
Concillian said:
Without some way of measuring the DC side, you don't.

The reviewers who calculate efficiency have devices that you plug the power supply into, then cords that go to the computer components and everything on the DC side gets measured by that device. Casual users like you and I don't have those devices, they cost more than an expensive power supply, so it would never make monetary sense to buy one.

If you give me:
- what you're seeing from the wall on your meter
- how much your electricity costs per kWh (mine is tiered, and we are in a tier where it's about 35 cents per kWh, while the initial tier is only 11.5 cents per kWh... big difference)
- Brand and model of your current PSU

Then I can calculate the rough savings you would see from a different PSU and you can look at whether the Return of Investment is worthwhile.
Click to expand...
No, it is not using a computer as a load. It uses a special device to provide the load.
 
theAnimal said:
PSU calculators tend to overspec already, so no point in doubling.
Click to expand...
Yes they overspec if you go tinker with the cap degrading overclocking and such. But if you fill in just basics like a person should they dont overspec with much.

Yes you can work out its efficiency without equipment. Somebody already put the psu through its paces. Now can pull up the Eicos report and see how it did. You will notice at 50 percent load the effeciency is always the highest.

So again OP give me the PSUs name and model so I can show you how to do it
 
Concillian said:
Without some way of measuring the DC side, you don't.

The reviewers who calculate efficiency have devices that you plug the power supply into, then cords that go to the computer components and everything on the DC side gets measured by that device. Casual users like you and I don't have those devices, they cost more than an expensive power supply, so it would never make monetary sense to buy one.

If you give me:
- what you're seeing from the wall on your meter
- how much your electricity costs per kWh (mine is tiered, and we are in a tier where it's about 35 cents per kWh, while the initial tier is only 11.5 cents per kWh... big difference)
- Brand and model of your current PSU

Then I can calculate the rough savings you would see from a different PSU and you can look at whether the Return of Investment is worthwhile.
Click to expand...
Yes your almost there!!!

So if someone already tested the model of the psu all we need do to do what now to get its effeciency?
 
Concillian said:
The reviewers who calculate efficiency have devices that you plug the power supply into, then cords that go to the computer components and everything on the DC side gets measured by that device. Casual users like you and I don't have those devices, they cost more than an expensive power supply, so it would never make monetary sense to buy one.
Click to expand...

Ahh... This is what I was wondering.

I know you can get the voltages on each on the line 12v, 5v, 3.3v etc using a multimeter (as per the sticky thread) but I would also need the amps to work out the wattage used?

I have to take the PC apart tonight to install my new cpu cooler so will find out the make and model of the psu.
 
what brand/model is your PSU? You might be able to find a review/test of it. But if it's > 5 YO the efficiency is probably around 60-70% depending on the PSU build quality.
 
depends on the load its been carrying. If its been at 50 percent it would be more. Caps dont degrade so quickly depend on the quality
 
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