Sodium lights draw a very large amount of electricty, require a special transformer, and are expensive to buy and run. They heat the room they illuminate much more than do fluorescent lights of any design; while perhaps advantageous for some plants, this is not desirable for winter-growing plants. Sodium bulbs also diminish in light output over time and must be replaced regularly. I was going to let this go, but most of this paragraph is just plain false. Sodium vapor lights put out far more usable light per watt than fluorescents and less heat per watt than fluorescents (as a corollary), although they do burn hotter than fluorescents. Needless to say, they heat the room less than fluorescents for the same amount of useable light. Fluorescent tubes also diminish in light output over time as does every lighting fixture I know of. Fluorescents also require a special transformer that goes by the same name (ballast) as those for sodium vapor lights. Both can be driven by "electronic" current limiting devices instead of ballasts, saving some wasted heat. The reason they use ballasts is they are plasmas and will exhibit thermal runaway (as will mercury vapors, metal halides and LEDs) in the absence of current limiting devices . Tungsten and tungsten halogen both have negative feedback (increased resistance) with heat, requiring no ballast, and both are black body resistance emitters rather than emitting in special wavelengths. Tungsten halogen is more efficient than tungsten because it can burn much hotter since a halogen gas mixture scrubs the emitted tungsten off the bulb surface and re-deposits it on the hottest part of the filament, building up the thin parts of the filament and extending its lifetime. As this is a finely engineered phenomenon, they should never be used with a dimmer (as is true with the ballast type lamps). I was going to replenish my fluorescents when I saw 70 watt sodium vapors at Lowes for $42 each and there was no way I could match that economy with good fluorescent grow lights.