Measuring power

[Andrew Beattie]

This is a long way off topic but I'm hoping that someone here might be 
able to share a clue...

I need to measure the power used on dozens and dozens of servers.

I need a breakdown by server, not a total for the room.

(more specifically, I want to calculate the power cost per server per year).

Added difficulty:  I want to do this non-intrusively.

I can't go round, yanking out cables and inserting in-line meters.

So, I got a clamp meter.  But contrary to my expectation, that only 
works if I can separate the individual wires in the power cable - not an 
option.

So, I'm stuck.  Is there any non-intrusive way to measure the power 
consumption of my servers?

Andrew