Actually, I just put a used HP ProDesk 600 G3 Microtower (Pentium Gold G4560) into operation, and my energy meter shows 0.0W most of the time (which can't be true, but apparently it's something <1W) with Ubuntu + TLP installed and the HDD in standby.

Here are my TLP settings:

  TLP_DEFAULT_MODE=BAT
  TLP_PERSISTENT_DEFAULT=1

  # Change some BAT settings back to AC defaults
  CPU_MAX_PERF_ON_BAT=100
  CPU_BOOST_ON_BAT=1
  CPU_HWP_DYN_BOOST_ON_BAT=1

  # Disable options that are undesirable for servers
  MAX_LOST_WORK_SECS_ON_BAT=0
  WOL_DISABLE=0

  DISK_DEVICES="sda sdb"

  # Leave disk power management to hd-idle ('PM_ON=on' means PM off, obviously /s)
  AHCI_RUNTIME_PM_ON_BAT=on
  DISK_APM_LEVEL_ON_BAT="keep keep"
  DISK_SPINDOWN_TIMEOUT_ON_BAT="keep keep"

I use hd-idle for spinning down the HDD (sdb) because the shucked WD "White Label"/Ultrastar He10 apparently doesn't care for APM or Standby Timer settings set through TLP:

  echo 'HD_IDLE_OPTS="-i 0 -a sdb -i 1800 -l /var/log/hd-idle/hd-idle.log"' >> /etc/default/hd-idle
  systemctl enable hd-idle.service

Besides that, I had to

  systemctl disable udisks2

because udisks2 wakes up the drives every 10 minutes, no configuration possible. Also, smartd (from smartmontools) shouldn't wake the HDD if it's in standby, but it will reset hd-idle's standby timer, so I tell smartd to run every 24 hours instead of 30 minutes:

  echo 'smartd_opts="--interval=86400"' >> /etc/default/smartmontools

Probably best to measure power in the DC side of the power supply to be sure it's under a watt...

Measuring AC power is very hard to do accurately - there could for example be something else in your town injecting a bit of power at some other frequency onto the AC power grid (for example 1000Hz), which your PSU ends up absorbing (due to filters in the input of the PSU). Regular power meters will usually only measure the 50/60Hz component of absorbed and reactive power, and can therefore over/under read.

Still good to know some desktops are designed with power consumption in mind!

> which can't be true

Yep, but still not <1W. Even at 20% load the PSU have only 80-90%% efficiency.

Just test with something with a low and known power usage, like a LED lamp or something.

Actually, that's exactly what I did and the energy meter will gladly measure a 1W LED bulb. That's why I think consumption is <1W most of the time. At the end of the day, everything <5W or even <10W would be pretty great.

BTW, there are very short bursts of 1W~10W every second. And FWIW, after ~24h, the energy meter shows 0.0117kWh. Obviously, these measurements are a far cry from lab precision, but they do give me some confidence that I won't really notice the server on my next energy bill.

except for storage.

My home server is mainly my home NAS.

It would be hard to put 12TB of mirrored storage in a laptop.

While there are laptops which accept 3 or even 4 SSD's, and which could do this task, those are very expensive, so few might have one handy.

Older ARM SBC's had many limitations in the number of PCIe, SATA and USB 3 interfaces.

Nevertheless, now a much better ARM CPU has become available for cheaper devices (i.e. in the $100 to $200 range), the Rockchip RK3588 (quadruple Cortex-A76 + quadruple Cortex-A55 + triple Cortex-M0).

For now, this is the only ARM CPU with a decent speed, comparable or better than the Intel Gemini Lake Refresh CPUs, except for the much more expensive NVIDIA Xavier or Orin, or the Qualcomm Snapdragon SBCs, which are much more expensive than Intel/AMD CPUs + motherboards, having similar features.

There are at least 5 or 6 companies who have announced boards with RK3588, ranging in size from credit-card size, like Raspberry Pi, to the larger picoITX, and up to the miniITX form factor. Hopefully such boards will be available in the second half of 2022.

Some of these boards have up to 4 SATA connectors, besides an M.2 NVME SSD slot, so they could be easily used as a NAS.

According to the published reviews of such a board, the typical total power consumption (without SSDs/HDDs) is around 5 W, and the peak power, at maximum CPU utilization, around 13 W.

My Synology NAS use an ARM: I chose badly: very few video format are supported..

There are a lot of different devices that include ARM cores.

Some of them have actually been designed for TV set top boxes as their primary application, e.g. most of the models from Rockchip. These support a lot of video formats in hardware, even more than typical desktop GPUs from the same year. For example the Rockchip 3588, launched this year and used in many single-board computers that have just been announced, is one of the first devices providing a fast hardware AV1 decoder, besides decoders and encoders for all older codecs.

However, some of these devices with ARM cores have vendor-provided video drivers only for Android, to be used in smart TVs, so it may happen that the device used in your Synology NAS actually supports in hardware more video formats than you can use, and you are limited by the available video driver, which is incomplete.

With a 2012 gaming laptop then there is a chance it'll have dual SATA bays. If there's an M.2 slot as well, then it might be doable.

I have a T430 with an external USB3 dual disk caddy, with 8TB disks, soon to upgrade to 16TB.

An HP MicroServer uses laptop-class components in a different case.

Not sure what generation you're referring to, but my HP Microserver (Gen 8) has a 17W TDP Intel Xeon cpu (E1220v2 iirc) and an HP SmartArray controller, and HP iLO baseboard management controller.

I don't think that stuff qualifies as "laptop-class".