As solar becomes cheaper and cheaper, low efficiencies may still be worth it. We're never going to power a 747 on solar, but if the energy in the fuel comes fro

As solar becomes cheaper and cheaper, low efficiencies may still be worth it. We're never going to power a 747 on solar, but if the energy in the fuel comes from the sun, even if 90% of that is "wasted," it's still greener.