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Energy Cost of EV vs IC Engine

Are electric vehicles cheaper to fuel than gasoline vehicles? It is a question that came up while thinking about the Electric Cruiser Concept. Lets do some statistical analysis and find out:

Some givens:

* United States Dollar (USD) is the monetary unit.
* My household power bill was used for the cost of electricity. I have included all taxes but not my flat monthly fee of $5.50. Electric costs may vary widely based on region.
* Gasoline cost is estimated at $2.50 per gallon. This includes all taxes. Gasoline prices are volitile and vary widely based on region.
* Natural Gas cost is also provided for comparison purposes. All taxes have been included.
* All energy units will be converted to Joules.

Energy Source: price per unit x unit per Joules = $ cost per Joule
Electricity: $.062062 per KiloWattHour x .0000003725 KiloWattHour / Joule = $2.309x10-8 per Joule
Gasoline: $2.50 per gallon x 1 gallon / 121000000 Joules = $2.07x10-8 per Joule
Natural Gas: $3.57 per Therm x 1 Therm / 105000000 Joules = $1.68x10-8 per Joule

So electricity turns out to be the most expensive source of energy. But energy cost is not the only factor. To know the actual cost we need to take into account the inherent innefficiencies of the two propulsion/storage systems. Gasoline engines are generally not more than 30% efficient. An efficient electric charging/storage/power system could end up costing less to power dispite it's higher energy cost.