A low-end x86 CPU will perform better than the RasPis. My current NAS is an Intel G4560 with 40GB of RAM and 4 HDD and it barely does over ~40W on average. The article's cluster does 18W which is better, but even over a year that's only a 192kWh difference (assuming that is runs all the time) which would amount to about 40$ at $0.20/kWh.

It's not really worth comparing further as the configuration are significantly different, but if your goal is doing 110MB/s R/W, even when accounting for power consumption the product in the article is much more expensive.

I don't know much about NAS and thought they were just a bundle of drives with some [media] access related apps on a longer cable ... 40G RAM? What's that for, is it normal for a NAS to be so loaded? I was looking at NAS and people were talking about 1G as being standard (which conversely seemed really low).

G4560 suggests you're not processing much, is the NAS caching a lot?

40G is purely overkill and is not utilized. Initial build had 8G and then I had 32G lying around so I added it.

4G is probably enough. Though nextcloud does use a lot of memory for miniature generation.

As for the G4560, I can stream 1080p with jellyfin so it packs a surprising punch for it's power envelope.

Even for mainsteam x86 Intel chips idle power consumption is mostly down to peripherals, power supply (if you build a small NAS that idles on 2-3 W on the 12 V rail and can't pull more than 50 W, don't use a 650 W PSU), cooling fans, and whether someone forgot to enable power management.

The HP 290 idles around 10W.

Picked one up off craigslist for ~$50 and use it as a plex transcoder since it has QuickSync and can simultaneously transcode around 20 streams of 1080p content.

I hear it's still possible, through heretic magic, to limit a CPUs power draw and most importantly, it will not affect speed on any level (load will increase).

There's even people selling their souls to the devil for the ability to control the actual voltage of their chips, increasing performance per watt drawn!

But only Gods and top OSS contributors can control the power draw of chips integrated into drives/extension cards/etc

The linked machine uses a 2W processor.

The successor product on the company's site uses a 12 volt, 2 amp power adapter: https://www.bee-link.net/products/t4-pro

Here is a YouTube review of the linked model with input power listed at 12 volt, 1.5 amp (link to timestamp of bottom of unit): https://youtu.be/56UA2Uto1ns?t=129