If you're going by the wattage specs on-line, especially on eBay or Amazon, they are bogus - - sort of an ad war with no basis in actual wattage (which actually means very little as it correlates to actual light output in lumens.
As an example, I purchased a 54" Nilight (link below) with a claimed 312 watts (the formula for watts is Watts = Current X Voltage) so at a nominal 13 volts, one would expect the light to draw 24 amps (26 amps if input is internally regulated to 12 volts). I measured that to see. With 13.3 volts I measured 16.4 amps, or 218 watts. So much for truth in advertising.
BTW, the light is very bright and I'm pleased with it so far. Link:
NiLight LED bar
I made the light mounts (shown before painted black).
