coal is and will remain for a long time the cheapest source of energy we had. nuclear is easily the cleanest we have but it's so bogged down with regulations and people who know nothing but fear everything keeping it down it'll never be cheap and easy to do.
solar and wind are both still developing, and both still require equal output from traditional plants to make up for times when it's... you know, not windy or dark outside. there's a huge expense associated with having a traditional plant sit idle that's never taken into consideration with "solar panels on your roof"... with commercial wind, it IS taken into a consideration and that's what drives it cost way up.