Originally posted here

IMHO Electronics ballasts are pieces of *rap. You will find very, very few electronic ballasts used commercially, indi ustrially or by coomercial or resrach horticuturalits. They are just another product that through deceptive advertising and unscrupulous marketing has become a new fad product. They produce less PAR, alterred wave lengths, electronic interference, they under drive the bulbs and tend to end up melting. Yes they use less o poer, but that is because they provide less usable light. Yes they run cooler beacuse they use less wattage. Yes the bulbs last longer but only because less power is run through them and they are underworked. Lees in usually means lees out and electronically driven bulbs reflect that.

My Apogee meter shows a marked PAR decrease below the plant canopy much greater with electronic ballst lighting. Lux readings are higher.
The follow test results are on a 175 watt halide with three or four different electronic ballasts and a stadard magnetic ballasts. The charts clearly show better performance by the magnetic ballast. It supplies more blue spectrum wavelength lighting and less of the undesireable wave lengths of the unusable wavelenghts. So even though the electronic ballasts can be said to produce more light it is in the areas of less desireable wave lengths so therefore a bad thing not a good thing beacuse it is producing lees light in the desirable ranges in oder as well. Tests with other halide bulbs all tend to show the same lighting wave length alterationsby the electronic ballasts. Halide bulbs simply put are designed to produce the wave lengths that are desred when the bulbs are fired by magnetic ballast. Electronic Halide ballasta are the bastard children of haide comonents. They prove only to be good when deceptively advertised as less proper wave lengths mean poorer yield and potency regardless of LUX or candlepower or wattage. Less undesireable light means less desirable growth. Ecelectronic ballast also produce less intnse lighting so the PAR at a distance is lower so unless you have air cooled or water cooled bulbs yor Par anywhere below about 2.5 to 3' below the bulb will be dismal. PAR drops off at a rate that increases by the initial loss times the distance square. Ie if you loose 5 percent at 1 foot (1^2= and 1 x 5% = 5%) at 2 foot (2^2 = 4 and 4 x 5% = 20%)you will loose 20 percent and at 3" (3^2 = 9 and 9 x 50% = 45%)you will lose 45%. This is especially important as the electronic ballast loses the initial amount at a larger percentage. These are not real numbers but consider if the electronic ballasts initial loss is 10% instaed of 5%. That would mean at 2 feet that the loss would be (2^2 = 4 and 4 x 10% = 40% and at 3 foot (3^2 = 9 and 9 x 10) = 90% or nearly no usable light.
http://www.advancedaquarist.com/2005/12/review