How many watts to run double fluro light?

Answer 1

It depends on the type of double fluorescent fixture and the tubes you use in it.

If you use regular T-12 tubes, you would use 80 watts plus whatever losses you get from the ballast (up to 20 watts).

If you use energy saver T-12 tubes, you would use 68 watts plus the losses from the ballast.

If you use a T-8 fixture, you would use 64 watts plus whatever losses from the electronic ballast which are next to nothing in comparison to a magnetic T-12 ballast.