Power supply efficiency

The last few weeks I have been working on different projects for industrial robots, and while working on that I came across some genuine power supplies, and then decided to test the efficiency between the genuine and copy.

To test that I use two mains power meters, and use the average between the two (I don’t have a high end meter for that, so using two different brands and models should in theory be more accurate than using just one), and to load them I will use my Re:Load Pro electronic load.

The first I will have a look at, is a genuie Delta Electronics DRS-24V50W1NZ. It is a 24V power supply, made to be mounted on a tophat DIN rail.

Delta Electronics DRS-24V50W1NZ

Load Watts (230V~) Watts (24V=) Efficiency
0 A <1 W 0 W N/A
100 mA 3 W 2.4 W 80%
200 mA 6 W 4.8 W 80%
400 mA 11 W 9.6 W 87.3%
600 mA 16 W 14.4 W 90%
800 mA 22 W 19.2 W 87.3%
1.0 A 27 W 24.0 W 88.9%
1.2 A 32 W 28.8 W 90%
1.4 A 37 W 33.6 W 90.8%
1.6 A 42 W 38.4 W 91.4%
1.8 A 47 W 43.2 W 91.9%
2.0 A 53 W 48.0 W 90.6%
2.1 A 55 W 50.4 W 91.6%

Siemens 6EP1332-1SH43

For this one I had a look in the datasheet, because I had expected it to be more efficient, but it actually isn’t that far from what they claim.

Efficiency at Vout rated, Iout rated, approx. 88%
Power loss at Vout rated, Iout rated, approx. 8 W
Load Watts (230V~) Watts (24V=) Efficiency
0 A <1 W 0 W N/A
100 mA 5 W 2.4 W 48%
200 mA 7.5 W 4.8 W 64%
400 mA 13 W 9.6 W 73.8%
600 mA 18 W 14.4 W 80%
800 mA 24 W 19.2 W 80%
1.0 A 28 W 24.0 W 85.7%
1.2 A 34 W 28.8 W 84.7%
1.4 A 40 W 33.6 W 84%
1.6 A 45 W 38.4 W 85.3%
1.8 A 50 W 43.2 W 86.4%
2.0 A 56 W 48.0 W 85.7%
2.2 A 61 W 52.8 W 86.6%
2.4 A 66 W 57.6 W 87.3%
2.5 A 67 W 60.0 W 89.6%

And the next one is one from China, ordered off eBay, with the mandatory spelling errors on the label, so chances of this being a copy is pretty high.

Mean Well DR-30-24 (China clone)

Load Watts (230V~) Watts (24V=) Efficiency
0 A 4 W 0 W 0%
100 mA 6 W 2.4 W 40%
200 mA 9 W 4.8 W 53.3%
400 mA 14 W 9.6 W 68.6%
600 mA 19 W 14.4 W 75.8%
800 mA 25 W 19.2 W 76.8%
1.0 A 29 W 24.0 W 82.8%
1.2 A 35 W 28.8 W 82.3%
1.4 A 40 W 33.6 W 84%
1.5 A 43 W 36.0 W 83.7%

Oh dear… Even with no load on, the cloned power supply is drawing 4 W on the mains side. With the Delta Electronics it was so low I could not measure it, which is why I had to put N/A into the efficiency for it.

Both power supplies are as expected not that efficient at low loads, but the Delta Electronics quickly goes up, and already at 600mA it is around 90% efficient. The cloned Mean Well at 600mA is only 75.8% efficient, which should be opposite, as it is only rated for 1.5 A, where the Delta Electronics goes up to 2.1 A instead. So the copied power supply is in percentage higher up the scale, and should be more efficient on lower loads.

The best efficiency on the copied Mean Well is 84%, and at a 1.4 A load, where the Delta Electronics topped at 91.9% at 1.8 A load.

After reaching maximum load for each power supply, I let them stay there for 15 minutes, then tried to touch them. The Delta Electronics power supply I could barely feel any heat from, but the copy Mean Well was definitely starting to heat up.


  • Could you open them up and see what quality the caps are in both? 🙂

    • Inside the Mean Well there are Taicon and YST branded capacitors, and in the Delta Electronics one they have used Ltec branded capacitors.

      • Thanks for the check! I had an asus motherboard that blew some caps (Ltec brand) about 10 years ago. Not sure if they’ve upped their game since then 🙁

      • LTEC = Luminous Town Electric Company. [China]. Pretty bad reviews from what I read. That’s sad 🙁

        • The Delta Electronics power supply was a pretty cheap one too, but from a reliable supplier. It only cost me $22, and I only got it because my order was too cheap, and I would then have to pay $20 for handling, and then I would rather get something than just paying for nothing. 🙂 I got a little Siemens power supply at work, I will see if I remember to borrow it this week, then test that one too.

    • In the Siemens power supply I just added, they use Rubycon capacitors.

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