Let's see how that works out. Wikipedia says there are 240 million cars in the US. That means we would need 240,000,000 acres of sunflowers to power all our car

Let's see how that works out. Wikipedia says there are 240 million cars in the US. That means we would need 240,000,000 acres of sunflowers to power all our cars. World Factbook says the US has 9,161,966 sq km of land of which 16.29% is arable or 1,492,484 arable sq km. With about 247 acres per sq km, we have 368,643,612 acres of arable land which means about 65% of the arable land in the US would have to be devoted to sunflower production. On the other hand, those solar panels can go anywhere.