This is a mounting box for a VA meter that I got to monitor the printer at any given moment.
This mounts on the top using the existing frame bolt.

Here's the meter I used:

Choose the one with the 50A shunt.
http://www.amazon.com/gp/product/B00GJKAYZQ

RepRap

FolgerTech Prusa i3

No

No

.2mm

20%

Print box face down with no supports.