I've heard 'kill-a-watt' is good but I use a 'Watt's Up'. It will connect to a PC and give recorded data over a long period, pricing, voltage & piles of other stuff but costs 5 times as much.

www.doubleed.com
www.wattsupmeters.com/

Thanks for the links !!

I was just in to a local tool house asking if anyone was making a watt recording device with a RS232 interface.

Of course USB is better as it is
the updated serial interface.

Where IS that 'Theory of Everything' ?
Here
it is !