The U.S. energy supply in 2007:

 
Source: U.S. Energy Information Administration 

As we live it, we depend on fossil fuel (petroleum, natural gas and coal) for 80% of the energy in the U.S. Fossil fuels are non-renewable which means they run out. We take from deep in the earth, burn and release greenhouse gases into the atmosphere for electricity and transportation. We're impacting the atmosphere in an adverse way. 

                    Coal is dirty - yet plentiful and cheap

                    
                  Garbage is what we make of it

 
                                                                             The wind is clean and free.