Nice project 
I've always wanted to know exactly how much energy I'm using, and now I'm just days away to get my own solution working
I do not have any experience in Arduinos, but I plan to use an ATmega(8,16,32), I'm not sure what will suit my application best. Those computers do have UART interface and that is good news since the old laptop I uses as home webserver has a RS232 (serial) interface. The plan is to buffer the meter reading in the ATmega and send to laptop (server) and perhaps use another ATmega coupled with a DS1620 digitalthermometer. And then correlate used energy with outdoor temperature
Python and pySerial is quite easy to use when interfacing with UART.
I tried various solutions before ordering some ATmega.
The first try were 6-7 years when I studied, my apartment had the meter in my office/study, and I used my (only) optical mouse and taped it to the meter with the optical sensor right above the light, and were able to make a Java program that registered changing states in the serial transfer. It was a bad solution since I were a student and a new mouse would cost too much.
Just recently I tried to use a photoresistor and photodiode with a parallel port to do the same trick, but i was not able to get any stable signal through.
Mmmh, should perhaps have something measuring the take wind speed also...