Would such an application of the technology be feasible?
That's a difficult question to answer without knowing the type of energy usage to which you refer. I will say that I am unaware of any sensor designed specifically to monitor energy usage. Some RFID transponders have an input/output port allowing a user to connect external sensors, so that when the tags are read, they would transmit data from the external sensor. So you could connect a device monitoring energy usage to an RFID transponder, and allow it to communicate energy consumption when the tag is read.
If our loyal readers have any information regarding transponders that measure energy consumption, please post it below. Thank you.
—Mark Roberti, Founder and Editor, RFID Journal