My home server using a very similar configuration (same CPU, a lot less potent network) is what enables me to work from home, making a living, so the cost of electricity is compensated by the gas saved on commuting. I am also in process of adding solar to my house, covering a lot more than this server.

If people use old servers in the kilowatt range consumption for fooling around having a server in the basement is questionable, building something with low power in mind is nothing to complain about.