Magnetic ballasts use less electricity? but run more hot?
Electronic ballast run cooler, and use less electricity(I think Madmanmac mistyped "less" instead of "more"). You can also use SE or DE bulbs w/ an electronic ballast. For $192.00-6% at captivereefs.com you can get a 250watt "plug and play" retro kit w/ an enclosed electronic ballast w/ two built in fans, parabolic reflector w/ a mogul socket, and bulb. Not to mention the choice of 10, 14, or 20k bulb and a three year warranty on the ballast. No wiring, no need to build a ballast enclosure, no ballast heat problems, etc,. When you add everything up, those DIY
units end up costing close to, if not just as much as a retro kit IME
. Factor in the extra energy usage, and it may end up costing more and more in the long run. HTH