Potential issues with this test:

1. It appears that this test was performed on a cold day since people were wearing jackets prior to the start of the test (maybe they were anticipating a cold car). It would be worthwhile to record the exterior temperature so we would have a good understanding under which circumstance it is better to open the window vs. use the AC. Air conditioners cause much higher engine load when the outside temperature is higher. The reason is that the compressor has a higher duty cycle and higher working pressure during hotter conditions.

2. It appears the test was performed at speeds of around 45MPH. At 45MPH, there isn't a lot of aerodynamic drag on the vehicle. For example, at 65MPH there is over twice the aerodynamic drag of 45MPH. To do a valid comparison for highway conditions, the test should run closer to a more realistic 65MPH.

For testing:

Consider a comparison test under actual road and weather conditions. For example hot weather on the highway, and in urban conditions as well.

Use two identical vehicles on the open road driving the same route. Switch travel direction, drivers, vehicles, and chase vs. leading vehicle to eliminate those variables.

They revisited this, and the speed and drag was addressed. It was discovered that under 50 MPH, drag is not an issue and windows down is more efficient, but over 50, drag becomes an issue and air conditioning is more efficient.

OK, I'll need to search for that one.

Thanks,

-Charles