The goal of this study is to add to the understanding of the overall emissions caused by cars using both gasoline and existing alternative fuels. We will include the emission from the vehicle itself and also from upstream sources, primarily the source of the energy used to actually move the vehicle. The fact that electric motors have better efficiencies than internal combustion engines and the fact that power plants usually have higher thermal efficiencies than an engine seems to suggest that that the electric vehicle will be the more efficient in terms of emissions per vehicle kilometer. The complexities of vehicle propulsion become evident when one compares all the details of the available options, such as electric vehicles have to transport extra weight in batteries to increase performance. In this work we evaluate the emissions from electric and gasoline vehicles that are on the road. The data shows under most conditions the current vehicles have lower emissions than gasoline cars in terms of kilograms of carbon dioxide per kilometer. The different propulsion systems are then evaluated in how they would perform in moving a standardized vehicle including the system itself through a standardized cycle, to assess whether differences in emissions are the result of the system itself or other design differences. This study found that while in general the electric vehicle is better, the source of the electricity is a crucial factor in the determination. It is found that the cars currently being produced produce less green house gases than the gasoline cars on the average. In fact two of the four cars performed better even at the highest possible emission levels. While this casts a positive light on the electric car, it is a simplistic way of looking at the data. The calculations also show that the performance levels of the gasoline cars are much higher than the electric cars; this could be the main reason for the lower emissions of electric cars. The second part of this study is focused on quantifying the differences in emissions by studying that from a standardized car in all 50 states and D.C. These differences arise from the different levels of emissions owing to the variety of combinations of methods used and the methods themselves in the generation of electricity within the 51 regions. An analysis is done on of the most efficient car that could be made with commercially available products. The results show the dependence of actual emission on the energy source. Although the national, California, Florida and lowest averages all beat the performance of the gasoline vehicle, the gasoline car won if the electric car was operated in D.C. using electricity generated in the D.C. Results for the electric car in all 51 regions and for the gasoline car have been obtained. There is an implication that lower specific power would result in more states where electric vehicles will emit more green house gases. Assuming that new cars do use the higher specific power batteries, electric vehicles will produce less green house gases than gasoline vehicles at a national level.