This was sourced from http://forum.wordreference.com/showthread.php?t=1620395 and adapted from the contribution by Imber Ranae dated 1st december 2009:

electric = runs on electricity eg. electric car, electric fan, electric appliance, electric guitar etc. It’s also used metaphorically to mean: exciting, energetic eg. the atmosphere at the U2 concert was electric.

electrical = having to do with/concerning electricity eg. electrical engineer, electrical wiring, electrical tape, electrical shortage, electrical energy etc

I’m sure there are many exceptions, of course, such as “electric company” for the organization that runs a power-plant. Sometimes the two words may be used interchangeably, as in “electrical/electric shock”.