Originally Posted by Simpte 27
But if you existing ballast only pushes 15 watts for a 24 inch bulb (like most of your typical "all glass" hoods) the extra wattage is wasted.
I don't consider it wasted. I mean if your ballast is rated slightly below the wattage of the bulb, you simply aren't using the bulb to it's full capacity. Within certain limits (difference between ballast and bulb wattage), you would still benefit from the better efficiency of the bulb, and so still get more lumes out of your 15W with this bulb than you would with your older T8 bulb. If on the other hand your ballast is above the bulb wattage you are simply overdriving the bulb, IME up 2x overdriving is quite efficient and doesn't present a lot of loss to heat.
Regarding T5 Vs Compacts, they are the same technology (bulb), infact in many markets one is called a T5 and the other a folded T5. Just like folded T8s have a different code name, they are the same as linear T8s. Many self ballasted CFs sold as regular bulb replacements also carry the T5 marking. There may indeed be differences in some of the ballasts, but the ballasts can be used on either type of bulb giving the same advantage or disadvantage regardless. I haven't done this yet however I'm sure the workhorse ballast that is sold by AH Supply will power a linear T5, just like it powers VHOs, CFs and even T8s. There's a lot of marketing hype behind bulb technology and ballasts but as long as we stick to electronic ballasts and the power ratings are close, you should be able to run just about any bulb on any ballast. Better ballasts will give you better frequency, cooler temps, more lumen per watt.... but this is so regardless of bulb you hook them up to as long as wattage and distance between the contacts is within the ballast's capability. So in the end, a better ballast will make just about any bulb perform better, and a better bulb will perform better than a "lower" bulb on the same ballast.