Speaking on Deep Background, the Press Secretary whispered:
Concur with you need wattage not amperage. There is a 'relatively' cheap
method of doing this however local electrical codes may put a damper on
this type of project.You put a current transformer on each branch circuit. A 'typical' current
transformer will generate 1Millivolt per Milliampere. You then install a
A/D board in a PC and write a simple application to query each channel of
the A/D. or purchase a commercially available SMNP datalogger.
I assume Alex is looking for a boxed solution. If not concur
it's Not Rocket Science [TM-Click&Clack] to build a system. You
can do the voltage sensing safely. {My too-early AM thinking is
that there will be too little phase shift in an unloaded Voltage
Transformer to worry about.}
You'd need a VT per panel leg, but a CT per branch circuit.