Elcellent information Dutch.

I saw you post it last nite on the other thread, but had no time to comment. It shows the difference between magnetic and electronic ballast to be even less then I thought.

Also thought that the power usage of the electronic ballast was higher then I thought but I took the opportunity to check a Lumatek 600w ballast last night, and was surprised. It was clocking 634 watts total usage to drive a 600w HPS bulb. As eye's example of a 600w magnetic showed a 690 watt use the savings is less the 60 watts.

Between what I know of the 1kw mags I'm using and seeing thier 600w numbers it is pretty safe to say an old fashioned iron core ballast uses abt 15% over bulb wattage. And that most electronic ballasts are not 99% efficent as I once thought.

Considering your older then dirt, not a bad find at all.