Are any of the M73's you have equipped with the Intel Pentium G3220T 2.6GHz CPU?
Purchased two of them listed as:
Lenovo ThinkCentre M73 Tiny Desktop Core i5-4590T 2.0GHz Quad 8GB 500GB HDD WiFi
Way cheap for Haswell chip set (less than $200) and appear to be brand new to me.
There are many on Ebay off lease except that most of them are Intel iSeries generation 2-3.
The i5-4590T is same power of 35Watts as the i5-G3220T. The i5-4590T was a higher priced Haswell chip.
Someone locally is selling a used one for CDN$170 (~US$132) with G3220T CPU, 8 GB RAM, 120 GB SSD, and Win 10 Pro.
That is a very good price for the Lenova M73 with a Haswell chipset with 8Gb of RAM and an SSD drive.
My current main automation server running HS3 today is old now and using a Haswell chip set mini ITX board iSeries and 16Gb of RAM. It is doing HA in Ubuntu 16.04 Linux and running one Oracle Wintel VB doing some more automation that only runs in Windows.
The other automation server running HS3 is running on a Pine64 2Gb computer (ARM - $35) running Ubuntu 16.04 64 bit server. It is very low powered. It is larger than an RPi. That said updating it to a Rock64 with 4Gb and a 32Gb eMMC drive. It is around $50. Waiting for a design change that includes a battery RTC. Note that this computer will not run a Windows OS at this time.
Been doing a sort of hub and spoke slave and master computer automation thing using the extra RPi's that I have.
IE: one RPi2 is POE powered in the attic and using a ZWave GPIO card, SDRadio, 1-wire USB device and currently providing ZWave, NOAA satellite pictures and a 1-Wire hub for temperature and humidity sensors on the second floor rooms and hallway.
These two Lenova computers replaced two desktop Shuttle Net tops running with Atom 525's (way old) and have a much smaller footprint.
If so, how much power does the PC consume while idle?
I have not checked.
Also, can it auto-restart after power is restored?
yes.