For those of you who have been giving Clark some heat over his support of nuclear power, this note's for you: There are now plants generating solar energy by using rotating mirrors to follow the sun's path. These plants are popular in the Mountain West where there's fantastic sunlight. In fact, the sun gets so intense that Clark's brother -- who lives south of Phoenix -- has to flee to San Diego for about a month every year! The New York Times reports there are 2 of these mirror-equipped facilities already on the grid, while 8 more are in the planning or construction stages. It's good to know that there are new solutions on the supply side. On the demand side, meanwhile, Americans now are using less fuel thanks to fuel-efficient vehicles. Clark recently got a question about whether it was smart to ditch a 4-year-old SUV and buy a new fuel-efficient vehicle. The answer is no, you must instead buy a 4-year-old used fuel-efficient vehicle. Remember, let somebody else take the hit on depreciation.