Electric Car Math

I like the idea of electric cars.  I am an engineer from a family of auto mechanics; several uncles, one grandfather, and my father worked in his brother’s shop for years in his youth. My father taught me how to do auto maintenance, and I have done the basics myself for a long time.

In my home, I have a gas snowblower for my long driveway.  I have a gas lawn mower for my yard.  I have a gas leaf blower for the leaves.  I have a gas chainsaw for the trees on my land, half my acre is wooded, and my driveway passes through my mini woods.  I have a gas brush cutter to clear the many invasive brush plants that live on and around my land.  I have a gas generator for when the power goes out thanks to those trees, and those on my street.  Last winter alone, winter storms killed power for a total of 8 days from December 2017 through March 2018.

One of those winter storms knocked what I thought was a healthy tree across my driveway killing the tree of course.  Fortunately the tree was only 5 inches in diameter.  Unfortunately for me, that same storm knocked the power out to my home as another tree on my street was blown down.  My wife was out of town, and so in order to leave my driveway, let alone to clear the snow off it, I had to clear it while keeping my 3 year old out side.  Obviously, I am not going to use a chain saw with him walking around.  I had put him in my car with his tablet so he could be safe while I used the electric one.

The gas chain saw would not start anyway, as I had been trying to get it running for months.  It is a cast-off from my aging father in law, and a cleaned followed by a new spark plug did not get it running.  I suspect my father in law did not put fuel stabilizer in it.  How much I hate ethanol in our fuel, and those of all the mechanics I know, is a whole other article.  One day I will do an article showing how we use more energy in creating it than we get by burning it in our vehicles, and the extra problems it causes far outweigh any supposed environmental gains.

So with him in the car and no electricity, my options were my cord electric chainsaw, or my handy ax, another great cast-off from my father in law.  I cleared a path to move my gas generator close enough to the fallen tree so that I could connect my extension cord to my generator to use the chainsaw to cut the tree.  The chain was old, and needed replacement.  I have used it often, and being human, I have forgotten to get a new one.  Now I could buy teeth sharpeners, and it would save money to use those files to sharpen the teeth of the chain saw, but we all make trade-offs.  For my time – money analysis, it’s saving enough money to do the work myself, as opposed to hiring someone to do it.  So if I waste a few buck on a new chain each year, while saving hundreds cutting up such fallen trees and branches myself, I will call it a win.  Besides, I have no problem using my metal file sharpening the ax blade.  Well, this chainsaw, after all of that was useless.

By this point, my son was very curious, and bored with his tablet.  While he was bundled up and quite warm, I checked on him periodically, what daddy was doing was far more interesting.  I gave up, and went with my trusty ax, clearing the tree in not much time at all.  So much for machines saving time as I had hoped to do.

Of course what I didn’t mention is that to use my generator, I still have to make sure that it has the correct oil for the operating temperature.  The wrong one can hurt the engine, and shorten it’s lifespan.  I have a nice dry erase board in my garage safely mounted above kid level where I keep the information on the last I did my oil changes, and what oils for what temperature ranges of all these tools.  It’s a time consuming hassle, and we haven’t gotten to the two cars yet.

So what is my point, I love the idea of battery powered tools and vehicles because of the significant reduction in maintenance.  Not having to worry about the oil changes and in the case of the brush cutter, the right mix of gasoline and oil, is a huge time saver.  It all adds up.  Sure I can do it, but it’s not fun.  I don’t mind getting dirty, actually, emotionally, it’s a way to connect to my relatives, some of whom have passed away.  It’s just a hassle.

My big problem with electric cars has always been that they remain, today, not cost effective.  That does not mean that one should not own one.  Just because the savings in “fuel” costs does not usually make up the difference in the cost of the vehicle, does not mean one should not own one.  My long story about all those engines is my way of making one valid point in that they are easier to maintain.  I know 3 people with Teslas, and a few folks with other branded electric vehicles.  I am a software engineer living near NYC, so there is a lot of them around me.  So, maintenance savings is one realistic reason to own one, even if total cost of ownership is not.

Then there is the fact that they use less fossil fuels to operate. I do not care to get into a discussion about the pros and cons of the climate change issue.  However, if you are such a person that does see it as an issue, then there is some positive effect in using an electric car over a gasoline powered one.  The truth is, though, it’s not nearly as much as you might think due to the amount of energy used to make the car, and to salvage what you can from it after the car is done.  The big problem is the battery. Electric batteries are good, but they are not there yet, which is why all those tools I mentioned are not battery powered, yet.  I firmly believe that someone will solve the battery problem soon enough.  One company in China is making the rounds of tech articles these days saying that they are the latest to have “solved” the problem.  My skepticism is warranted as many others have made such promises in recent years, but I do believe someone will solve it.

Another reason to buy one over a gas car is that they are more fun to drive for a variety of reasons.  Electric motors have maximum torque at all speeds, more or less.  That means that they can accelerate like a rocket, and that is just plain fun.  That is a reason to own one.  I am sure there are many others.

The problem that  I have is when articles like this like about it.  The author even tried to forestall some of my coming criticisms with a few statements trying to account for what I am about to say.  The fact is, though, he was misleading.  He lied.  I take issue with people who deceive others who may not be as good as they are with math or science.  It was that anger that prompted this article.

My primary issue with what he wrote is the fact that he compares national average gasoline prices to California electric (around the highest in the nation) to show that electric cars are not cost effective on fuel prices.  That is faulty logic.  Gas prices and electric prices, when compared to the National Average, tend to be proportionally the same in the country.  Due to varying electric generation options, and fuel taxation levels, there are some exceptions to that rule.  For instance, New Jersey, thanks to it’s refineries and low gas taxes had high electric rates and low gas prices.  Gas taxes went up recently in New Jersey to make them more in line with the electric prices, and the taxation rates of neighboring states.

In the article, the author correctly states that the average American drives roughly 1,000 miles a month.  The generally accepted range is 10,000 to 15,000 miles a year.  He goes on to state that the SUV he was promoting gets 39 MPG, and thus burns about 25.64 gallons per month.  At the time of his article, the National Average gas price was $2.61 per gallon, so the price for driving 1,000 a month in that SUV is $67 or about $804 a year.  To be clear, I am paraphrasing a paragraph of his in this paragraph.

Using Car and Driver’s data, they said that the Tesla Model 3 is rated at 130MPGe, and their tests showed that number to be only 84MPGe.  The author in the critical article used California’s $0.26 per KWH of electricity.  Now to make the math clearer, we need to know how many KWH of electricity are in a gallon of gas.  Fortunately, wikipedia has the number for us; 34.02And I turn to the US government for electric rates by region and state with data reported as of August 2018. They said that the national average for residential cost is $0.12 per KWH.  Please note that rate includes taxes etc.  So, then an apples to apples comparison in prices is NOT $0.26 per KWH, but $0.13.  I included the rate chart so that you could see how your state and region averages out.  Here’s a link to the US government for national average gasoline rates.

Anyway, back to the math that I love so much.  The Tesla is rated at 130MPGe, so 1,000 miles divided by 130MPGe gives us 7.69 gallons of gas.  If we use the lower number from Car and Driver, then it’s 11.9 gallons of gas.  Multiplying that 34.02 KWH of electricity per gallon of gas, we get 241.46 KWH to drive 1,000 miles or 404.84KWH if we use Car and Driver’s lower number.  Now we have to multiply that by the $0.13 dollars per KWH in National Average cost, and we get $31.39 and $52.63.  So that means his number of $67 to drive a Tesla is in correct even if we use the lower Car and Driver number.  Now if you use home charging, my numbers are good.  If you use Tesla’s supercharging network, then you have to check this link.  Tesla’s rates vary by state and by the amount of power you take.  They charge more when you have more than 60kW; usually double.  California’s rate for comparison is $0.26, and that makes it about $0.06 above the retail rate average for that state.  According to AAA, Californians pay $3.628 as of this writing.  Do you see where  I got annoyed?  Do most people charge at the superchargers, no.  They are intended to be used for long distance travel, not the way we use gas stations.

So being fair, unlike that author who had may out links to the SUV in question, hmm, electric cars do save some money compared to most gasoline cars when you factor in fuel economy. The problem is that the in 10 years, that difference will unlikely make up the difference in sticker price.  What about oil changes and related maintenance that electric cars don’t have, well there is something to that?  Still, I have not been able to accurately calculate that.  Most new gas cars, aside from an oil change, do not need much in 10 years that a Tesla would not; namely tires.  Still, I am not sure, so until I have data, I will leave it to sticker price, and call that a tie.  My instinct is to say that electric cars would save significantly, but again we have to compare it to equivalent cars, so maybe a Honda Civic or a Toyota Corolla?

There are other problems with electric cars, though.  Winter is the big one.  This article covers it very well. They illustrate how much energy is lost due to heating the battery and the cabin for these cars.  My suggestion is that if you live in a cold area as I do, to keep the thing in your garage to save money.  You will also need new tires, as the Tesla comes with summer tires.  This matters, and will easily set you back another $1000.  Then you need to store the tired that are out of season, and if you don’t have a garage to put them in, then you could be set back $50 or more per season.  Some places in the NY area charge much more than that.

So to sum up my points here, there are many reasons to buy an electric car.  Operating one is cost effective in most seasons in most parts of the US.  Do not expect to normally charge your electric car in fueling stations like gas cars, and putting a fast charger in your home will cost you $1000 to $2000. A gas car of the same class has a lower sticker price, and currently has a lower total cost of ownership.  That difference is narrowing, and the crossover point appears to be coming soon for most US locations. I hope it’s within 5 years, as I hope to get 5 more years out of one more of my cars.

I want to make one further point.  As I am in a place where I lose power due to fallen trees or limbs regularly, in a sustained power outage, it will be a significant issue to have an electric car. My only option would be to buy gasoline, to power my generator to charge my car battery.   That is not reasonable, and why my wife and  I decided at most one of our cars can be electric.  It’s worth mentioning that our local gas stations all have backup generators.  This is something that was proven during Hurricane Sandy. None of the local superchargers had electricity for a few days, and there are many within 20 miles of my home.

I could go on and on with this subject.  I will stop here, but I would love to talk more in comments with anyone here.


  1. EVs do face a number of concerns which make them appear less cost-competitive than their traditional gas-powered counterparts. However, if you were to factor in the environmental impact, it would adjust the calculus more toward favoring the EVs. This of course depends on the fuel source used to generate the power stored in the EV batteries. If your local utility primarily burns coal to generate electricity, the environment likely isn’t benefiting. However, if you live in sunny California, or windy Iowa, your reduction in gasoline usage is being replaced by clean energy.
    I badly want an EV but my current living situation wouldn’t accommodate home charging and I don’t actually need a new car. In the coming 5 years, however, I would love to be the proud owner of a Tesla Model 3 or some equivalent EV.

    Liked by 1 person

    1. I believe you are talking about CO2 emissions. I do not see renewable energy as positively as you do. Its not horrible, but neither is it a panacea. If they can get fusion right, it would be. This will take a whole post, but even in sunny or windy places, its not so clear cut.

      Please take a look at lithium mining and battery recycling. The process is energy intensive. That is a knock against them.

      Then we have to talk about the electric grid. Transmission costs about 5-10% of the power you generate, lost as heat from the fact that copper is not a superconductor. Stepping the power up for transmission and back down for use eats another 5%. Charging your battery eats another 5-10%. Converting it back from the battery eats another 1-5%. Cooling and warming the battery pack eats 5% to 15% on extremely hot or cold days.

      Solar cells are very energy intensive to make and require nasty chemicals to do so. I made some in college. You have to heat the silicon multiple times during production.

      Both solar and wind can not be more than about 20% of the grid until you have a lot of energy storage to balance when they can’t generate power. Their capacity factor is low compared to traditional plants. You need lots of traditional plants running on standby or lots of batteries.

      Traditional coal/gas power plants convert about 45% of the energy in the fuel to electricity. They really are not good either, to be fair. The mining and drilling issues go without saying. Those plants advantage is that they have high capacity factors and can generate power predictability.

      My take on this, and the reason I avoided it in the article is that most of those concerns fairly wash each other out. Only fission nuclear, which to be fair has its own issues, it truly low CO2 and can provide base load. As it stands now, humanity can’t make enough batteries even for the US to switch fully to solar / wind / hydro in 100 years. There isn’t enough production capacity.

      There are potential solutions, and please understand I am a supporter of solar and wind and electric cars. Solar/wind can work in our grid at up to about 20% of production. Once we install enough energy storage, that number can go up. Right now, in the US, that number is about 2% or so, maybe a bit higher.

      Also, i did the math a while back. If we had enough batteries, then we would only need an area 100 miles square, about 1.5 x the size of the state of CT, if we used say the 4 corners area, to generate ALL US electric needs. I did that using the land use and panel quality of the best solar plant in the world at the time.

      So, while I share your enthusiasm, and probably will buy an electric car in 4 or 5 years, things are not so clear cut, yet.

      I will add that I do think that hot fusion reactors will be built commercially before we have enough batteries to build solar out past 10% of the grid.

      Solar and batteries continue to have technical improvements, and they may win out. I am for all of the above.


      1. Yes, CO2 emissions are what I was implying. Fusion would be the ideal solution and I see renewables as a bridge to that eventual pursuit.

        I see renewables as a great alternative to fossil fuel generation but agree it isn’t the best solution to reducing greenhouse gas emissions. Storage is another complication but makes the grid more flexible and resilient, though at what environmental cost?

        Fission nuclear is a great source of low-emission power but is exorbitantly expensive on a $/kW basis. However, well-run nukes average capacity factors in the 90%+ range. It’s hard to beat that for a base load resource.


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