It is almost impossible to achieve those numbers, specially the idle, and the load we can only to be close to them when we use the watt/ per-useful-instruction metric.

recentest hw will have decent idle consumption (n95 is around 2w) but the rest of the hw will consume more and usually you attach more powerful/energy hungry devices so expect <10w in idle and perhaps <25w under load.

Older hw could not be so bad under load but they will idle less and will consume more