Well lets see, one 35 watt incandescent bulb, vs about 5-8 20 milliwatt LEDs.
Um... a red low power LED is about 2 volts at 25 mA max, or 50 milliwatts. However, even 10 of these little buggers isn't anywhere near as bright as a 35 watt incandescent. You wind up with a 5 watt LED to get sufficient brightness for a nav light, which is about 3 high power LEDs in series on a single substrate. That's 6 volts and to get 5 watts you wind up running not quite one amp into the device.
Reality check on these numbers says that an incandescent bulb is about 3 to 4% efficient turning energy into light and an LED is 10-12% efficient doing the same. That seems to jibe ... the LED is about 3x as efficient and draws 1/3 the current for the same apparent brightness.
One thing the LED DOES have going for it is that the light starts out red or green or white and doesn't need an optical filter (colored lens) in the way to filter out the colors you DON'T want. That increases the efficiency quite a bit.
On a 12 volt system that 35 watt bulb is drawing about 3 amps. The 5-8 20 milliwatt LEDs are drawing about .096 amps.
Um ... not quite. 8 LEDs drawing 25 mA each is about 200 mA (0.2 amps) and as I said above, nowhere near as bright as the incandescent.
Using 12v LEDs as opposed to mV LEDs removes the need to waste power through a resistor.
Um ... there is no such thing as a 12 volt LED. Incandescents with tungsten filaments have a positive temperature coefficient -- the more current that runs through them the hotter the filament gets and the resistance of the filament goes up which causes the current to go down which causes the resistance to go down ... and this little dance continues until milliseconds after the light is switched on, the current stabilizes and you have a constant VOLTAGE device. LEDs aren't so nice...a red LED has a forward voltage with a current that becomes exponential with forward voltage, so you wind up running a constant current through them to stabilize them. One GOOD way is with an external current limiting resistor, or if you don't like that, you can mickey around with a constant current power supply which takes a bit more room than a half inch cube.
Also, the required circuitry to make the LEDs flash, such as Strobes, is much lighter in weight, and way smaller. A very simple circuit to build and repair, very few components, and fits into about a 1/2" cube.
Um ... the control components may fit in a half inch cube IF you use SMD devices and little tiny passive components but you still need a power control device that will dissipate a few watts, so you need something with some heft to it. There ain't no free lunch.
