It's all about the cost. Oil is roughly $80 per barrel ($0.50 per liter). And a barrel yields roughly half a barrel of gasoline. So the cost per liter for gasoline is roughly $1.00 per liter, Synhelion estimates they can get the cost of their fuel down to about $1.00 per liter by 2030. Probably optimistic but still competitive. Although it's not clear which type of fuel that refers to. I suspect that cost is their operating cost. The initial capital to start a solar fuel plant is likely enormous. Supposedly they already have a commitment from Lufthansa. That's would be great if jet fuel could be made this way since no retooling would be necessary no only for jets, but also trucks, trains and ships.