I've Become a Computer Power Miser ... and I Like it!

[Winemaker]

My Dell 4100 bought in 1999 has been on since I bought it, although I shut the monitor off when not in use. It is no longer online, and I use it strictly for accounting for investments and rentals.

 

[mpeirce]

OK. The Macs work better than the PCs. No PC desktop I have ever owned does that.

All iMacs get down to ~1W when they are sleeping, even the iMac Pro.

iMacs vary a lot in their power usage, the iMac Pro can use up to 370W when fully decked out (2.3GHz Intel Xeon W processor, 128GB 2666MHz DDR4 ECC memory, 4TB solid-state drive (SSD), Radeon Pro Vega 64 graphics processor with 16GB of HBM2 memory).

Regular iMacs use a lot less power especially when idle (but not sleeping). Apple has a page with the details:

https://support.apple.com/en-us/HT201918