my home depot has 150 & 200 (5.5k lumens)watt cfls, they go in mercury mogul bases, if that is what you are looking at, I would go with the smaller ones (like 26w like repherz says) or 85w (still use standard lightbulb size mogul base). from my experience the larger ones require a 175w mercury ballast (they are meant to replace the 175w MV) and (obviously), not cost effective, stick to the 26w-85w range, otherwise just buy a HID light.