Currently using a 400W sodium light in an outdoor floodlight fixture.
I'm not sure how many watts it actually uses; probably close to 500W
and although the bulb is very efficient the fixture is not. So I'm
thinking about one of these (haven't decided which of the 2 yet):

http://store.yahoo.com/pro-lighting/4lat5flhibay.html

http://www.fullspectrumsolutions.com...res_35_ctg.htm
(the 4-lamp version)

What do you think? The fixture from FullSpectrum has a more efficient
ballast, but the energy payback would take a long time. Also I wonder
if the included 5900K lamps produce enough red spectrum for efficient
use as a grow light. Of course I could pull 1 or 2 of the lamps out
and keep them as spares and replace with 2700K or 3000K tubes.

Bob