I am fortunate to live in an area with some of the cheapest electric power in the USA (about 5.6 cents per kilowatt hour), so I don't worry about power consumption very much. My
Blue Iris server, as in just the PC itself, runs in the 110-130 watt ballpark. It is a mini ITX built around an i7-8700K, with two hard drives and an SSD, and a GT 1030 graphics card to feed the 4K TV. There would be quite a bit of energy savings if I underclocked it or went with the non-K edition that doesn't clock as high in the first place, because clockspeed and power consumption do not increase linearly. Each step up in speed costs more power than the last one.
Of course, I also have a whole lot of cameras. 21 of them connected to one managed PoE switch which reports 75 watts consumption at night, plus 5 more connected to other switches, so about 100 watts for the cameras at night. Add in the few IR illuminators and power consumption of the network gear itself and we're probably pushing 130w again just like the BI server. So lets call it 260w total. That comes out to about 190 KW/h per month, or $10.64 at my rates.
All things considered, this is a cheap hobby. If I was into motorsports or something, I could easily spend an order of magnitude more on equipment and fuel both.