Can I use a cfl to replace my metal halide?

First off, where are you using this? If you are talking about a Hi Bay, there are going to be some more effecient ways for you to lamp your facility. But if you are using a flood light, you are using the most efficient thing you can use for the light needed. There are CFLs that will screw in but you'll need to bypass your ballast since screw in cfls are integrated.

To your question, you are going to get your most lumens with a plug in cfl and those really only go up to about 6000 lumens. So, there is just not a CFL out there that works on a 220 or 110 for that matter that will offer an equivalent light output as the metal halide you are using.

If you are needing this for a hi bay, you could start using a T5 fluorescent and these would decrease your energy usage by about half.

Holly Eddins