What exists for super high efficiency, lower wattage power supplies? Ideally in the 300-400W range, if not 275W. Both SFX and ATX form factors are fine.
I’m trying to avoid rackmount-oriented PSU in particular unless they are provably silent (or silent at 2m) at 150W – likely 100-120W – or lower load. For example, total system idle may be as low as 40W. Cost not really a factor, but ideally shouldn’t be bananas (like 2-3x price) for TCO reasons.
For connectivity I need the usual ATX 20+4, CPU 4-pin, and four Molex connectors for a storage backplane. Modular heavily preferred, but not required.
80 Plus Platinum power supplies are rare in lower wattages, and I’ve yet to find a Titanium one. Corsair has the SF450, but with 115V I may only hit 91.5% efficiency under my expected load (150W or less is expected peak), and only 85-87% efficiency at idle (probably 40-45W).
Seasonic has the Focus PX-550, but since the expected load is so low, efficiency is considerably worse compared to the Corsair SF450.
Seems like a strange question to ask, when there is an authoritative list anyone can look through:
Except for two things…
Try buying a power supply certified in 2014 in 2022. They’ve not been made in years!
Check the actual measured efficiencies in reviews of those higher wattage PSUs. I have. The reason I bring up the Corsair SF450 is it has the best measured efficiency at very low loads.
This isn’t a “guys, can you Google this for me” question. I’ve been searching for days. Probably 15+ hours alone on searching for PSUs, their actual availability, and poring over reviews.
Running a 600 to 750W PSU at that would maximize their efficiency.
Every review I’ve checked from Aris Mpitziopoulos seems to indicate otherwise at very low loads. We’re talking as low as 40W idle and peak loads under 150W – probably only 120W – at 115V.
Hence why I’m trying to look for smaller power supplies (actually still for sale!) where I can be closer to the peak of the efficiency curve, which is usually 50% load.
So far the Corsair SF450 seems to be on top, at 85-87% near my idle load and ~91.5% at my peak load. I also can actually buy one.
No. They’re not actually more efficient. Yes, you can get very good efficiency at 450W with 920W SuperMicro PSUs, but not at very tiny levels of power consumption. Again, we’re talking 40W idles and sub-150W peak loads – very likely under 125W at the wall at peak load.
The Corsair SF450 was mentioned not because it’s the first thing I’ve found, but because it’s likely the best thing out there factoring in TCO. Including tonight, I’ve done > 18hrs of PSU research.
Although the 500W Titanium PSU recommendation is valid in theory, they don’t exist because the market for them is extraordinarily limited. A few are for sale … for +150-200% of the price of the Corsair SF450. From a TCO perspective it makes no sense. At $2.33 per year per 1W of electricity, you never recover the capital cost difference over 5 yrs for the expected 1.5-2% efficiency gain.
The obvious future (not here yet) solutions might be ATX12VO power supplies, as their very low load efficiencies are much better, and idle power consumption would be lower. However, PSUs are very rare at this point, as motherboards. Zero motherboards I’ve considered support ATX12VO.
Another idea is a 12V power supply, and I’m looking into it, but they’re not turnkey for my use case.
What you’re looking for is the HDPlex 400W. There’s no way to reach the performance you’re looking for with a conventional PSU.
They’re calibrated for higher loads, the conversion to different voltages like 5V and 3.3V causes loss in efficiency and operating on 120V makes it even harder for a unit to be efficient.
While a constant voltage output PSU like a Dell 400W brick + HDPlex 400W DC-DC converter is way more efficient and should lead to more efficient low load power consumption.
I guess that for the efficiency you’re looking for the 12VO standard is the one that would do the trick, but doesn’t seem like you have anything compliant to that standard.
92% is pretty common for single rail AC/DC supplies, 94% can also be found/custom ordered.
In order to not kill efficiency by double-conversion (because then 92% * 92% = 84%), put two isolating AC/DC supplies next to each other. One for the main and one for the minor rails.
ATX12VO is just Intel’s attempt to standardize the different 12V PSUs used by Dell, HP and Lenovo. Instead of building a system from components, you could start with one of those…
However, 12VO is a gimmick anyhow. Your PSU will be rated higher efficiency, but since things like USB ports require constant 5V, the efficiency loss will be in the voltage conversion on the motherboard, which is just not an efficiency number people check for, unlike PSUs. ATX12VO should have been ATX5V/12VO.
And there are alternatives to ATX12VO, like:
…Seasonic’s CONNECT module. This does effectively the same as the ATX12VO standard, removing the 5 V and 3.3 V rails from the PSU and moving them to an external module, off of the mainboard. It can be fitted into the area behind the mainboard in many computer cases, making for very clean cable management. It also allows for increased efficiency. Intel’s ATX12VO Standard: A Study In Increasing Computer Power Supply Efficiency | Hackaday
For PC power supplies it’s not that common due to the load curve they’re calibrated for and, as you correctly said,
My suggestion of using a Dell power brick was also due to the fact that laptops, as much as they can be power hogs, are also designed to run at very low power states so the load curve of one of those PSUs is more like a slope starting from low loads and ending towards higher ones.
Sure there’s some loss at the DC-DC converter with the HDPlex but it’s a less powerful circuit compared to a 400W SFX PSU (took the 400W nightjar from Silverstone as a comparison) so it’s more efficient.
I have the 300w 80+ Bronze and it is silent. I can not hear it over the CPU fan running at idle.
Its driving a GTX 970, Ryzen 3600, 32gb PC3000, and 256gb Samsung 970 Evo without breaking a sweat.
The challenge is that as you go up in efficiency the cost increase is often not worth the price on low wattage options. I would go for the 350w gold flex or 500w gold TFX.
Theoretical approach! NOT a suggestion!