The tutor continues to investigate energy alternatives. The comparison between electric and gasoline cars might depend on your point of view.

Someone told me a while ago that electric cars are 50% efficient.  I was surprised to hear that number, and didn’t necessarily believe it.  I remember reading, maybe in grade four, that the human body is about 40% efficient.  I have a hard time believing that a mechanical entity is more efficient than a biological one.

Well, first I had to check my facts. Eventually I did find confirmation at antranik.org: the human body is 40% efficient at converting glucose to usable energy.

Next, I found, from the US Dept of Energy, that electric vehicles are, in fact, about 60% efficient, while gas cars are about 19% efficient.

Here’s where the road forks: are you an academic or a consumer?

If you’re a consumer, the comparison is done: electric cars, at 60%, are about three times as efficient as gasoline cars. The next step is to compare prices, to find out which might be the bargain. Energy prices can be volatile; however, my July 29, 2014 post found that gasoline, diesel, and electricity, per unit of energy, may have surprisingly similar costs.

If you’re not interested in the cost, but rather the true energy efficiency from an academic point of view, the comparison between electric and gas vehicles must go further. Where did the electricity come from? If it came from burning fuel, then you need to factor in the efficiency of that process as well.

The US Energy Information Administration suggests that more than 86% of electricity in the US comes from fuel-consuming plants (this includes nuclear power). Around a third is from natural gas. I’ve done a weighted average of the efficiencies of the various sources (based on information found here) and come up with an efficiency figure of roughly 35% for the generation of electricity in the US.

So, if your electric car is 60% efficient, but the electricity you use to power it is produced with about 35% efficiency, the realistic energy efficiency of the car is 60% of 35%, from an academic point of view. It finally works out to 21%. Remember: gas cars are around 19% efficient. To an academic, the electric-vs-gasoline efficiency might be compared as 21/19, or 111%: the electric car has 111% the efficiency of the gasoline car.

To a consumer, the electric car is roughly three times as energy efficient as the gasoline one. To an academic, the two are much more similar, the electric car having 111% the gasoline car’s efficiency.

Which side speaks to you?)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.