Electric Versus Gasoline

 After the previous post, I got to wondering: since I said we weren't burning gasoline to make electricity (and so the comparison was not exactly fair), what would the real CO2 comparison actually be?

Let's crunch some numbers!

Basic Figures

For the purposes of this calculation, we'll make the following assumptions:

• We're going to send our gasoline and electric vehicles 50 miles.
• The electric will consume 350 watts per mile.
• The gasoline vehicle will go 15 miles per gallon (3.96 miles per liter).
• The electric will use coal-powered energy, at 2.32 lbs of CO2 emitted per kWh consumed.
• The gasoline vehicle will produce 5.09 lbs of CO2 per liter of gasoline consumed.

Why these numbers?  Because of the two vehicles I own, these are not outlandish and actually quite common consumption figures.  We'll play with numbers below.

The First Calculation

Given the above assumptions, our electric vehicle:

• will consume 17.5 kWh for the trip
• produce 40.6 lbs of CO2 (if powered solely by coal-generated energy)

Our gasoline vehicle:

• will consume 12.62 liters of gasoline
• produce 64.3 lbs of CO2

Some Codicils

Bear in mind these are estimates.  If the gasoline vehicle were to get closer to 20 MPG, it's CO2 output for the same trip would drop to 48.2 lbs.

There is also the reality that gasoline vehicles and electric vehicles operate almost opposite of one another: whereas an ICE engine increases efficiency as it runs at higher RPMs (such as when driving highways), electric vehicles benefit more from in-town driving (where they can use regenerative braking and are not going fast enough to incur meaningful air resistance).

If our electric is able to run at around 250 watts per mile, its CO2 cost drops to 29 lbs.  A comparable gasoline engine needs to attain 33 MPG to match that.  250 watts per mile is honestly rather low, but it can be achieved (as can 33 MPG or greater).

Conclusion

Bear in mind that all mileage ratings are based on very specific EPA standards, which are designed not to tell you how far you can really go on a tank of gas or a charge, but how one vehicle compares to another given certain standardized conditions.  These can include not running the air conditioning - and for those who live in hot climates, we all know how absurd that expectation is.

If we can power our electric vehicles with energy sources less-polluting than coal, our CO2 footprint drops.  For instance, if all our energy comes from natural gas, the same trip at 350 watts per mile will cost only 16.8 lbs CO2.  To get near that with gasoline, you now need to run at 57 MPGs - good luck with anything but the most fuel-efficient vehicles and the most careful driving!  If we switch to nuclear or renewable sources, game over.

While there is much left to be done to truly make electrics as functionally capable as ICE vehicles, the fact remains that in terms of power-options and their ramifications for the environment at large (which, of course, comes with a ton of assumptions we won't deal with here), electrics are quite literally the here-and-now future.

P.S.

I personally don't drive an electric because of environmental considerations.  I believe the interactions and inputs involved in our climate are significantly more complex than anyone is willing to discuss in open forum.  If we traded out all ICE vehicles for electrics tomorrow, we'd simply have a different set of problems, environmental and otherwise - not the least of which would include untold millions of tons of volatile lithium batteries in various stages of degradation.  Like I said, there is still far more work to be done on electrics, but we should not discount them or mock the people who own them.  There are economic opportunities afoot - the greatest fools are those who refuse to take advantage of them.

There was probably a time with everyone who owned horses scoffed at the new Model T rumbling down the road, and look at where we are today.