I found this site that has a carbon calculator
HybridCars.com - Gas Calculator and only one car beats my Toyota corolla 1.8L automatic. The Honda civic 1.3L boasts a 42mpg, but my Toyota really gets 36mpg all highway which is not much worse than the Honda. This site shows the price to be about $10,000 more than I paid for the Toyota-
2009 Honda Civic Hybrid Detailed Pricing and Specifications - MSN Autos and the rated driving range stated for the Honda is 553.5 mi. The only down side other than price which will not be reclaimed from gas savings for about 25yrs., is the Honda only has a 3yr/36,00mi basic warranty. (That is probably when the charging system will have major problems and who knows how big that chunk of cash will be.
I give it a big thumbs down.