Electric Car Energy and Carbon Tax Charges, Compared to Gas Vehicles

Electric Car Energy and Carbon Tax Charges, Compared to Gas Vehicles

The typical energy to miles ratio for electric cars is that 0.3 kWh (kiloWatt-hours) of electricity takes an electric vehicle one mile.  The inverse of this is that one kWh of energy will drive the car 1.33 miles.  

The CA greenhouse gas emission average in 2017 was 0.50 pounds of CO2 emission per kWh.

Greenhouse gas emissions for gasoline are about 20 pounds of CO2 per gallon.  

The energy for an average 15,000 miles driven a year for a commuter with an electric car is given by: 

15,000 miles x 0.3 kWh/mile = 4,500 kWh.  Multiplying by the California average of 0.50  lbs CO2/kWh gives 2,250 lbs CO2 of emissions for that distance.   Dividing by 2,000 lbs/ton gives 1.125 tons of CO2 for an electric car.  This CA average is also about the same as SC Edison’s.

An average gas car gets 25 mpg.  So 15,000 miles/25 mpg takes 600 gallons for the year.  Multiplying by 20 lbs emissions per gallon, this gives 12,000 pounds of emissions, or 6 tons.  Comparing 6 tons with gas to 1.125 tons with electricity gives a ratio of 5.33 for gas/electric, or 0.1875 electric to gas emissions.  So in California or with SC Edison, electric cars only have about 20% of the emissions of gas powered cars, for the same distance.

SC Edison has a discount rate for charging electric cars called TOU-D-Prime, which means a Time Of Usage rate.   The prime hours are to avoid the hours of 4 pm to 9 pm, when solar power is falling off, and both businesses and homes are using power.  During week days in the Summer, the rate is 14 cents/kWh.  During the Winter October to May, the rate is 13 cents per kWh.  During the forbidden hours, the rate is 40 cents an hour.  These rates apply regardless what you are using the power for.

For the SC Edison area, the cost electric power for the 15,000 miles is the cost of 4,500 kWh.  Multiplying this by $0.14/kWh is $630 for electricity to drive 15,000 miles.  The standard gas powered car uses 600 gallons for 15,000 miles.  At $4 per gallon, this costs $2,400.  Taking the ratio of $630 for electricity to $2,400 for gas gives 630/2,400 = 0.26, or roughly a quarter of the cost with electricity.  The savings is $2,400 – $630 = $1,770 a year.

I don’t know how long batteries last, but say that you keep the car for 10 years.  That means your savings are about $18,000.  That is far greater than the extra cost of an electric vehicle.  With just a fraction of that, you can invest in safe driving warnings and electronics.  It will eventually cover automatic driving software and devices, and also save you energy with smoother driving and lighter vehicles.

We now look at the cost of the Carbon Tax on both electric and gas vehicles for 15,000 miles.  We use the Citizens Climate Lobby proposal of an initial carbon tax of $15/ton of CO2.  We then also evaluate it after five years of $10/ton of CO2 increases, which adds up to $65/ton of 

CO2.  For 15,000 miles in a year, the gas car uses 600 gallons, and at 20 pounds of CO2/gallon gives 600×20 = 12,000 lbs, or 6 tons.  For electricity from SC Edison or the California average, we calculated above 1.125 tons of emissions.

At $15/ton of emissions at the start of the Carbon Tax, for gas we have 6 tons x $15/ton = $90 a year in tax.  For electric, we have 1.125 tons x $15/ton = $17 a year in tax.  The difference is $73 a year.

At $65/ton of emissions after 5 years of increases, for gas we have 6 tons x $65/ton = $390 in carbon tax a year.  For electric cars, we have 1.125 tons x $65/ton = $73 a year in carbon tax.  The difference is $317 per year.  


About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
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