How much power you can save (debian +mac mini/peplink manga/...?

Do you believe you can get a 3watts debian box? Those power saving 'geeks' show how amazing you can do with equipments on hand, as drawn in following lines:
Peplink Manga (integrated) 3.1 2.3 kWh /month
x86 laptop plus Linksys switch 24.3 ~ 17.8 kWh /month
Debian Mac Mini plus Manga switch 15.2 11.1 kWh /month
For more detailed info, refer to here