Here is a link to a older experiment ( albeit slightly biased to the manufacturers electronic ballast ... which is a dead link in that article btw )
http://www.animalnetwork.com/fish2/a...8/mar/product/
however it would seem that the electronic ballast draws less amps ... and if this is true then when this discussion came up with the Venki electronic ballasts and initially it was thought that there would not be much of a savings ... but if Venki's ballasts were even close to as efficient then one circuit only would be needed and you would save on breakers/wire etc
Food for thought
Cheers