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This file is saved at www.herringshaw.com/led.xls Let me know what you think.
In building my Electric Car (88 Mazda getting the Solectria treatment) I came across some LED taillight bulbs at Sherco-auto.com. You should check them out - connectors and other stuff for good prices. ANYWAY, So I wanted to see if there's a financial payback on these lights in a ICE vehicle, assuming of course that these could extend the range on an EV at night, which of course there is no price on!

My car has 4 taillights, so I bought 4 @ $5 each (combo tail/Brake Light) Check out the file to change numbers and see if you come up with something different - with my analysis, if you drive more than 12.5K miles/year with your taillights on, you'll have a 20% payback. Put that into Gasoline instead of Diesel, it'll do even better. What do you think on the efficiency #'s?

If you have to change a bulb anyway, then this is a no-brainer, but fun to analyze anyway. Make sure your Lens color matches the LED color - Make sure your bulb mount faces the bub toward the lens (not always the case, as in my car, so the LEDs are going into the Golf)

Assumptions - All in Green can be changed (download the file for changeables)

Conventional Taillight Bulbs 100 Watts [email protected] 27W (maybe 27 is the brake light, not the running light....)

BTU/KWH 3414
BTU/Gallon 130000 Diesel

Alternator Efficiency 70.00% [Turning Motion into Electricity]
Engine Efficiency 50.00% [Turning BTU's into Motive energy]

$/Gallon 3
Cost of Bulbs $20.00 4 - 27W Equivalent Bulbs



Taillights Used Per Hour
Watts used/hour 100
Efficiency Reduced Watts 285.71
BTU used /hour 975.43
Fuel used/hour 0.007503
$$/hour 0.022510

Overall Vehicle
$/hour @ 48MPG (TDI Golf) 3.75
% of cost going to Taillights 0.60%


Hours needed to drive in 1 yr to reach 20% Rate of Return 177.70
Miles Driven @ 75 MPH 12438.98


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