Through a collaboration with Hybrids Plus, ZAP is now offering a plug-in hybrid conversion kit for the Toyota Prius and the Ford Escape Hybrid. The company claims that the kits offer up to an astounding 120 mpg in the city and 90 mpg on the highway, though you'll certainly pay for it up front: the kits range in cost from $24,000 to $36,000, depending on the size of the battery pack and which vehicle you have.

Once you've recovered from the pricing, check this: You can plug the car and charge it using any regular wall outlet. The company said that today's hybrids, when stock from the factory, are still essentially gasoline powered vehicles. While they reduce emissions and gas consumption, they still run entirely on gas. The plug-in conversion kits change each car into a true hybrid that actually runs on two separate fuel sources: gas and electricity. Any development in this direction is good for the auto industry, but it's likely that even the most environmentally conscious drivers will balk at the system's cost.