Cost: Anywhere from $60 on up to the hundreds
MPG Improvement: 1 to 10 percent GPS units themselves are a great investment for the eco-responsible driver. They allow the driver to experience less time driving around lost, and they are able to generally calculated the shortest, most fuel efficient route to almost any destination you can imagine. So how could you make an already great product more green than it already is? Make it solar powered.One such solar powered GPS model is the i-Trek Z1. The Z-1 is a great all-around GPS which can be used for hiking, biking, and camping, but it is also capable of accepting turn by turn software for those who like to be told exactly where they need to go!