It's also ignores the fact that simply driving a car contributes to congestion, and the various network effects of that. More traffic means more pollution, more cars means less people are willing to walk or ride bikes due to safety, etc.

Food in general is a massively inefficient way to convert solar energy into muscular exertion. If you compare all the steps that occur from farming all the way to getting the food on your table, and then add in how inefficient our bodies are at converting food energy into mechanical energy, the results of the comparison becomes a lot less surprising. Electrical transmission, batteries, and electric motors are all very efficient by comparison.

How inefficient, what does massively mean? How do we demonstrate electric is 'very' efficient by comparison? Your list of electrical losses notably left out the power generation, which should be solar or wind, but in practice in the US is still a third coal, which does not compare particularly favorably to food. There are a whole lot of inefficiencies from end-to-end in both systems we're comparing here, many of which are really difficult to measure. What we do know for certain is that the amount of work that has to be done with a car is twenty times the amount of work that has to be done with a bike per mile of consumption, and a much much higher factor than 20x for production, which makes the suggestion that the car could be more efficient than the bike quite unlikely to be true, even though food production is inefficient.

Well okay, so I'm getting a bit off-topic with the whole "food is inefficient" argument, but if you look at the efficiency of photosynthesis it only harvests about 3%-6% of the light energy hitting the plant. A lot of that energy then goes to growing other parts of the plant that don't contribute to its caloric content (stems, roots, etc., or in the case of fruit, the entire rest of the plant besides the fruit). To get a ballpark idea of the numbers here, even biofuels have been found to be only about 0.3% efficient at converting sunlight to chemical energy, compared to solar panels which can typically harvest about 10% of the incoming sunlight into electrical energy. Plants are just not that efficient in general.

But efficiency of converting sunlight into energy isn't really what this argument is about, since we're more concerned with the CO2 output than the energy efficiency. The efficiency of human muscles factors in though, as it is only around 20%, compared to electric motors and batteries that are over 90% efficient. Regenerative braking is a big win for the electric car too, since it reduces the impact of the car's higher mass a lot. And when you look at the CO2 per calorie emitted by coal (and of course the US grid emissions are much better than this since we use many other better energy sources than coal), you get about 1.1g per calorie for coal compared to about 4.8g per calorie for fruit. So in a carbon emissions sense, food can also be much less efficient than electricity, even when that electricity comes from fossil fuels.

No single one of these factors is enough to tip the scales on its own, and of course the numbers can skew either way depending on what kind of food you eat, what kind of electricity you use, and many other factors. But I don't think the comparison is a totally crazy one.

Great point that solar efficiency is almost irrelevant to food's efficiency or pollution. The sun is shining anyway, whether or not we use it. Better to do anything with it than not. For that matter, CO2 is a big problem but not the only problem. I have no idea how electric and food compare there.

Regenerative braking is fantastic as an idea, but it does not actually offset the mass in practice. Tesla's regen braking has all kinds of limits - 64% electric conversion efficiency right off the top, but it also caps the regen rate, it doesn't regen when it's too cold, and regen can't recapture a/c or air friction losses, which actually add up to the majority of a car's power consumption for highway driving. I backed that up with data nearby. Regenerative braking is a great example of how cherry-picking efficiency percentages from the components of a system doesn't really help us understand the overall system efficiency.

Anyway, I don't know what the end-to-end system efficiency of food is, and to be honest I'm skeptical of anyone who claims to, the few stats we have are already gross approximations that tend to lose their context and their error bars. Combining them is extra problematic. My really one and only point is that the scales are pre-tipped 20:1 because of the mass on the consumption end, so no matter what happens in between, in order for the scales to balance, the complete end-to-end efficiency of electric system plus electric car manufacturing combined has to be more than twenty times that of food + bike manufacturing. No matter how good electric is, the savings are very much hampered by automobile manufacturing and by power generation. So it's just not that likely that the complete system for e-cars is a factor of 20 more efficient. There are multiple parts of the process that are the same or worse.

This is where I'm tripping up on this idea, too. The 20x difference in mass of a Tesla - but still more efficient than a human pedaling a bike may in fact violate the Laws of Thermodynamics. Also, I'm not sure if this is truly taking into consideration of the resources needed to make a Tesla vs. a bicycle. Or I guess the big one: the # miles/year driven by a usual car owner vs. # miles/year cycled by someone using purely human power to move oneself.

The car can absorb energy when braking, so the minimum expenditure based on the laws of thermodynamics is minuscule and irrelevant.

That’s an extremely tall claim, that minimum expenditure is minuscule and irrelevant, maybe taller than the original unlikely claim that a car might be more efficient than a bike rider. Regenerative braking does not invalidate the laws of thermodynamics, we just have to identify the regeneration efficiency.

So how much of the energy expenditure does regenerative braking in a Model 3 recover? From what I’m reading, it may be in the single digit percentages for highway driving. Tesla’s own web page says the theoretical max is 64% [1], and that’s only in a perfect situation (accelerate & immediately stop), it’s not accounting for driving for a long time without braking or using the electric features inside the car, e.g. aerodynamic loss, rolling loss, & heating & a/c. Wikipedia says including the accessories, typical best-case efficiency is around 50% [2]. But if you accelerate and drive for a mile without braking, you’ve already lost most of your initial energy to air & tires & battery conversion loss, the brakes can only capture energy from what’s left.

[1] https://www.tesla.com/blog/magic-tesla-roadster-regenerative...

[2] https://en.m.wikipedia.org/wiki/Regenerative_brake

You're proving my point. That's a big list of all the ways the car wastes energy that have nothing to do with the thermodynamic minimum to move the mass from point A to B. Those factors absolutely dominate the energy use.

Maybe an analogy is useful? There's a claim that you can cook 20 pounds of food in one type of bonfire setup with less fuel use than if you cooked 1 pound of food in a different type of bonfire. The amount of energy needed to actually perform the chemical changes on a pound of food, even multiplied by 20, is negligible compared to the vast quantities of energy that are going to other things.

Oh, you're right, I didn't understand your point before. You're saying that the thermodynamic minimum is a theoretical limit not approached in practice, right? It's not related to regenerative braking. The connecting "so" made me think you were saying that regenerative braking is the reason the thermodynamic minimum is much smaller.

It's more of "With thermodynamics we care only about the thrust to get up to speed. If we add regeneration then we can even factor most of that out, getting us to energy expenditures so very tiny that they're irrelevant to the total."

I could have phrased it better.

Got it, and likewise I could have not made assumptions and jumped to the conclusion that I understood your comment. I got lost between theory and practice. I think I agree with all of what you said when we're talking about theoretical limits and theoretical near 100% efficient regeneration. It's just that in practice, regenerative braking on a Tesla is not that efficient, and it isn't something that recovers most of your energy spent accelerating, it only recovers a minority share normally, and often only a very small minority.