Aris, good write-up, and thanks for showing the equipment used. I was not aware of the Newtons 4th group. I am in the power electronics industry and found your article spot on target. Here are my comments:
1. As technology improves, we always learn what is missing and learn to place better metrics on quality. What you are showing here is that PSUs, UPS systems, and other power equipment standards are way behind.
2. Had to laugh at your comment on running the PSU while cold. The UPS industry has been doing that for decades. Let it cool overnight, get an efficiency reading first thing in the AM, publish. The number is often 3-4% higher than reality.
3. There are MANY metrics missing including control overshoot/undershoot, hold up time, and now that there are digital controls, some are finding limit cycles (control loop oscillations) showing up at certain load levels. I had a PSU many years ago that the 12V rail would overshoot to 22V on power up!!! No wonder it kept eating HDDs. Some PSUs use the metal case to help with conducted EMI, so using some of the new plastic cases can cause mother board EMI issues. And how about finding a loading methodology that mimics how the user runs the PSU? A gaming PC is run hard for 4-6 hours a day, and then sits at idle for another 18 hours, or is even off.
4. On efficiency savings, we don’t include airconditioning savings. This is foolish, as it adds a whopping 40-50% additional losses to take those watts out of the building, depending upon where you live globally. This is the same for the newer light technologies (CFLs and LED), the watt savings advertised are only the direct usage, and does not include HVAC costs. So using a 33W LED bulb that replaces a 100W incandescent saves 67W at the bulb, and ~1.5 x 67W = 100W at the meter due to cooling costs. If this is in a spot where it is on 100% of the time, say kitchen sink light, that is saving $100 per year. Big difference! PSUs are the same.
5. Since PCs sit idle most of the time, the idle power is very important. And since the PC industry pushes having an oversized PSU, the idle efficiency of most systems is usually very poor. I have an HTPC that I built last year that now idles at 18W using a 250W 80+ Gold PSU. When I first built it and was getting it going, I used a 600W 80+ bronze PSU at first. That set up idled around 48W, which made me unhappy at first, until I realized I needed to change the PSU. So just grabbing an 80+ unit does not guarantee efficiency.
6. If the PC is turned off when not being used, the efficiency savings issue drops to mainly the Standby power. I had an old eMachines XP PC that had a power draw of 12W when off. Including the cost of HVAC, that was costing me ~ $18 a year just having it plugged in.
7. We should also be looking at the phantom draw of the UPS system that is attached, if you have one. I had a 7 year old UPS that the batteries failed and I noticed how hot the box was when I opened it. Did a power usage reading and found it was using 42W just running, no load. Wow. With HVAC costs, this is around $63 per year at the meter.
And then there are the losses found with cheaply built HVAC systems. Have you ever checked the air leaks in your air ducts? OMG! Forget the efficiency of the compressor. If you are conditioning your attic and crawlspace, the compressor numbers are useless.
Thanks again for your article.
- Charles