Quote:
Originally Posted by winkosmosis
IamIan, standard halogen headlight bulbs are only 55W each

Quote:
Originally Posted by gascort
New cars are probably less due to LED usage.

Just continue to adjust the general concept for the specific conditions you have.
All else being the same:
~40 MPH + ~40 MPG + ~500 Watt Lights = ~5.7%
~40 MPH + ~40 MPG + ~250 Watt Lights = ~2.8%
~40 MPH + ~40 MPG + ~125 Watt Lights = ~1.4%
~40 MPH + ~20 MPG + ~500 Watt Lights = ~2.8%
~40 MPH + ~20 MPG + ~250 Watt Lights = ~1.4%
~40 MPH + ~20 MPG + ~125 Watt Lights = ~0.75%
~40 MPH + ~80 MPG + ~500 Watt Lights = ~11.4%
~40 MPH + ~80 MPG + ~250 Watt Lights = ~5.7%
~40 MPH + ~80 MPG + ~125 Watt Lights = ~2.8%
~80 MPH + ~40 MPG + ~500 Watt Lights = ~2.8%
~80 MPH + ~40 MPG + ~250 Watt Lights = ~1.4%
~80 MPH + ~40 MPG + ~125 Watt Lights = ~0.75%
~20 MPH + ~40 MPG + ~500 Watt Lights = ~11.4%
~20 MPH + ~40 MPG + ~250 Watt Lights = ~5.7%
~20 MPH + ~40 MPG = ~125 Watt Lights = ~2.8%
etc ... etc...
Faster average speed decreases the impact.
Lower average MPG decreases the impact.
Lower Watts of electrical usage decreases the impact.
Higher ICE average efficiency decreases the impact.
Higher alternator efficiency decreases the impact.
If cycled through the battery the higher the battery cycle efficiency decreases the impact.