The efficiency doesn’t matter (to a point of manufacturing solar cells, or wind turbines, or whatever your equipment is for your renewable energy source). If all of the gasoline is generated from the air using renewable energy, it could take 100x the energy and still be completely carbon neutral. Carbon neutrality is based on the amount of excess carbon added to the air. If no carbon is added then by definition it’s carbon neutral.

Porsche already has a factory in Chile that is doing this exact same thing at a much larger scale.