A typical consumer router will take up something like 5-10 watts. A PC will suck in 20-50. Remember that the PC will be a lot more powerful so it’ll spend most of its time with low CPU usage.
Say the worst case scenario: 45W difference. 45W * (24 * 30) / 1000 = 32.4 kW*h/month. At $0.10 kWh rate that’s $3.24/month, less than a cup of Starbucks coffee.
You demonstrate a good worst case, but the article writer wants to use more than 10 gb/s so he can't actually use your typical router, he can have 15 gb/s with the MikroTik CCR2004-1G-12S which has an unknown idle W and a max around 50W.
Looking into the problem, I can't really determine why I should upgrade to 10 or 25 gb/s, but if I wanted to do so now I would rather buy components I could reuse than buy a router that will be inefficient for its entire service life.
Anyway I did the math and it would be $7/month. More than double your estimation, but still not horrendous. Although for that range of prices one might be able to find a managed instance machine in some cloud provider...
(edit: somewhere in the process I lost track of the fact this was a price _difference_ calculation, so it's adding $7 to whatever was already the cost with a more power efficient machine, which ofc. depends on number and type of HDs and other equipment)
If I add the cost for bandwidth and storage of a data center, then the economic choice is obvious.
A NUC or other Laptop hardware on the other hand would be OK to run. Maybe SSD raids are (financially) feasible for everyday files in the near future.
You are lucky to pay only $0.10. Here (Germany) I pay 0.30 Euro per kW/h. About $0.36 dollars.
I turned off my home NAS a few months back and partially switched to VPS services (also because of the better connection).
Yes, but switching to newer, more efficient hardware is not free, so you need to factor this in when considering a switch. Also, in case you don't only care about your wallet but also environmental impact it's getting even more complicated, since manufacturing your new shiny toy definitely is polluting the environment somewhere in Asia, gets shipped via ship burning horribly dirty fuel in international waters etc.
If you don't have any use for the old hardware, chances are it will end up burning on some open field somewhere in Africa after local recyclers already extracted the good stuff...
Thats true whether I use dropbox or my own server