I hate to tell you this, but depending on what area of the country you are in, they could be using fuel to generate electrical output. Plug in electric cars are not as "clean" as people would make you believe. Until the inputs for electricity are "green", eletric cars are not the answer. I truly believe in about 5-10 yrs(once storage is figured out) solar power would help with eliminating that concern, but until then, it's not green.