Urban Myths Part Deux: Keeping your gas car is better


OK, there is another urban myth which is, well it is obviously far better to keep my gasoline power car for as long as possible instead of getting a new EV. Or to ride the bus instead or take an Uber hybrid

Urban myth #1: I should keep my old gas car

This makes some sense, I should keep a very big expensive gasoline car forever because it would take years and years to make up for all that expensive manufacturing. After all, a car costs $30K and gas costs $4/gallon.
The reality is that those gallons are pretty horrible green house gas producers. So it is counterintuitive, but in the life of a car, the greenhouse gas cost of making the car is something like 10% of the entire lifecycle cost of using the car.
The net is that after about 5K miles in the average American city, you are actually reducing your greenhouse footprint a lot. Now why is this?
EVs are just much more efficient. The huge Model X is 89 mpg while the newer Bolt is 111 mpg and the Tesla Model 3 is 129 mpg. If you have a typical gas car which is burning say 22mpg, then it is 4.5-6.5x more efficient and that’s a huge win even if you factor in the use of “brown coal” in some places in the US.
So let’s look at the math, if you have say a 20mpg Toyota Highlander then the ratio of efficiency compared to say a 129 mpg Model 3 is 6x. That means that the crossover point is about 4,000 miles (the math is complex, so this is just an estimate) when you will “pay back” the carbon used to build the car. Actually in the Pacific Northwest, it is much faster since we are 100% hydro, so more like 3,000 miles. That’s pretty incredible. But when we get to myth #4, we will see the real marginal number is better.

Urban myth #2: I should just take the diesel powered bus instead or an Uber hybrid

Yes obviously, if you are walking or staying at home you are saving on carbon, but the other cases are a little surprising. If it just you and a bus driver on a seattle bus that gets 3 mpg in the city (https://www.reference.com/vehicles/gas-mileage-coach-bus-d76aa8c1b1f96084) is horrible. You r getting 12 mpg/pax. I’m sad to say that this is more common Than u think. The effective mpg is actually 20-40 mpg/pax assuming 3 city and 6 highway.
You need at least 45 passenger on average per bus to get to 135 mpg equivalent (3mpg * 45). Why does the math work this way? Well first, EVs are way more efficient in stop and go.
Still, using the bus is better even if gasoline because you so you do save on parking which is a big deal and since bus routes are sized for “peak” traffic, you can argue that your marginal footprint is actually zero since the bus would run anyway. But it is not as obvious as you would think because gas buses are really pretty inefficient (like 60x worse than a Model 3).

Urban myth #4: I will do better with a hybrid

Well sort of, hybrids do better because in city driving you are gaining on regeneration. That is why say a Highlander Hybrid is 28mpg city vs the regular Highlander at 22 mpg. So that’s a win, but the electricity you use otherwise is created by gas, so when you are on the freeway and the engine is running, the battery doesn’t help. Net, net, the ratio does change, so the savings are less 28mpg vs say 130mps is “only 4x better vs 5x” but the math is the same. For the average driver, it’s a six month payback.
So how does all this math work out in the real world. Well, right now I’m driving at 110% of EPA estimates (I can track Via teslafi.com) so in our crappy gigantic X I’m doing 95 mpg vs 89 mpg rated which is 86 city and 88 highway https://www.fueleconomy.gov/feg/noframes/39842.shtml) it is actually terrible by EV standards because it is so big and less aerodynamic batteries are heavier at 100KWh.
Let’s take some other cars and compare them at random. So if you have an old car like a 2008 Mazda at 18 city/26 Highway (https://www.fueleconomy.gov/feg/bymodel/2008_Mazda_3.shtml) and newer Honda Fit 33 city/40 Highway (https://www.fueleconomy.gov/feg/bymodel/2016_Honda_Fit.shtml) we crossed over in six months in 4k miles each or so. Also FYI unlike gas ratings which are massively gamed. The EV ratings are quite accurate except in the winter when the cold temperatures cause them to fall 20-30%.
As an aside, the new Tesla Model 3 is much better at with just 75 kWh battery getting 126mpg or 131 city/120 Highway (https://cleantechnica.com/2017/08/07/tesla-model-3-rated-126-mpge-long-range-option/). The Chevy Bolt is less because it is less aerodynamic but has smaller battery at 60kwh 128 city/110 highway  (https://www.caranddriver.com/reviews/2018-chevrolet-bolt-ev-in-depth-model-review-2018-chevrolet-bolt-ev-fuel-economy-review-car-and-driver-page-3), so these improve these figures by about ? that is the crossovers are shrinking

Urban myth #5: I’m in brown coal country it will never make sense

Actually this is not true, the analysis above assumes that every KW used to power an EV is “new” that is we were not going to generate the power to run an EV and so you have to burn more coal to get more EVs on the road. This actually isn’t true because of the way power generation works.
What actually happens is that there is a “base” load that is always on. You can’t store electricity and you can’t just turn off a coal plant. The big plants take literally weeks to start up. That means that at night, a lot of energy is just dumped. In fact in markets like Australia where you can “trade” energy, the cost of energy can actually turn “negative”. That is the utility will pay you to take their power because they have no way to turn off their generators and no place to put it.
So even in places that are dirty, if you charge your EV during non-peak, like at night at home, then you are actually using up marginally zero hydro carbons. You still have to pay the electricity company of course, but they were going to generate the greenhouse gases anyway. The net is that in this early stage where there are few EVs and it is not affecting the “base generation”, if you are disciplined and charge at night, you have the same 5K miles or so payback. So sleep well at night if you do this 🙂

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