Machines consume a baseline amount of power whether they're used or not; that power usage obviously increases with utilization, but ideally you'd have full utilization across the board.
If memory usage is so much higher than CPU usage, I have to wonder what it is that Mozilla is doing wrong with their architecture. Are they using pre-fork-style servers? Are they just provisioning poorly? What is it?
> CPU use is irrelevant to most internet servers.
Why? The CPU is used when the machine does anything. Ideally you're operating the machines at full capacity, less overhead to handle load spikes.
> Over the week, I operate my car engine at about 1.2% capacity. Maybe they should write about that.
What you're doing is inefficient, and they do write about that. The solution is called car sharing and public transportation.