The carbon footprint of Volvo all-day lights?

Question

There are squillions of Volvos trundling round the world, all with idiot-lights on all the time.
Ignoring the possibility (and it's only a possibility) that a safety purpose is involved to offset the harm, can anyone estimate how big of a carbon footprint these lights have?

Answer 1

The lights use around 20W
The engine is normally producing about 60kW
Assume efficiency loss of 25% (alternator, mechanical and transmission loss)
That represents an increase in fuel usage of approximately 0.04%
Or a reduction in fuel economy of 0.02 mpg.
Compare this with a reduction of up to 2% due to underinflated tyres, I don't think it is top of the hit list.

Answer 2

All the new cars in the US do the same. It's a safety issue.