Switching from incandescent bulbs to compact fluorescents (cfl) provides a two-fold benefit during the summer. why?

The Earth Policy Institute states that once the whole world shift entirely to compact fluorescent light bulbs,  we would be able to shut down 270 coal-fired power plants. Also, the gasoline equivalent of the energy that would be saved by replacing a 100W incandescent bulb with a 24W CFL is enough to drive a Toyota Prius from New York to San Francisco. Therefore, the two-fold benefit of swapping your bulbs are 1) it can save a lot of energy, and  2) can save you a ton of money, as well. 

Size and shape of continents