> I'm just curious, since these are specs and not real life, when running 
> CFL from a 12 volt source, what's the real power draw?  I gotta believe 
> they aren't as efficient at 12 V as at 110 V nor are they drawing only 
> the wattage shown on the spec for the light.  
As you imply, it is not the case that for a CFL fixture the light itself 
runs on the supply voltage. Rather that voltage, be it 115 V AC or 12 V 
DC is converted by the unit into what is needed to power the fluorescent 
tube. So what determines how efficient the light will be is how 
efficient the circuit is that does that. In general, I have found that 
CFLs always claim to be a bit more efficient than they really are, but 
the 12V models come closer to the truth than the 115V models do.

With LEDs there is a similar problem in that most of these LEDs need 
around 3.5-4 V DC. There is a further complication in that the current 
must be controlled very carefully and also with the high power LEDs 
temperature is critical and must be taken into account, and what's more 
the LED's must be protected from voltage surges or spikes much more so 
than with a gas tube.

So I would say that the limiting factor is not so much the circuits that 
supply power to the lighting device itself provided that efficient 
designs are used (which admittedly for cheap units is often not the 
case), but rather the limit will be reached more due to the 
characteristics of the light emitting device. -Ken
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