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Comment by Gravityloss | Hacker News Reader

The whole "liters per 100 km" or "g CO2 per km" approach doesn't work with plugin hybrids because it depends much more on the use case than with regular ICE cars.

Someone can commute completely with electric power and do a few longer trips per year, getting the average emissions way way down.

And someone else who can't charge at home or at work and who drives long distances daily might be using just as much gasoline as a regular car.

What are some good metrics instead of these emissions? Pure electric range? Charging speed? Required charging frequency with some typical usage profiles?

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It also greatly depends on how they are driven. I was chatting to a Lexus dealer a couple of years ago and asked about the claimed 5.5l/100km of the RX450h (SUV). He said "the way our customers typically drive, it's closer to 10l/100km". If you drive like a grandpa you probably can get the claimed economy, but most people aren't going to do that.

WLTP "high" is essentially "rural road in the summer with a 70-90km/h speed limit" - achievable, but not commonly the case.

It's attainable in eco-mode but no one will drive it only in eco-mode because it's so slow.

Source, I own this exact SUV.

In sport+ mode, I get close to what you mentioned.

I drive a 2007 station wagon like a grandpa. Average diesel consumption? 4.0l/100km. For those less into SI units, that's over 200 megabarleycorn per rundlet! [0]

Back on topic, PHEV's often get preferential tax treatment. My old car gets punished, barred even from some cities. That makes sense only if completely disregarding actual usage.

I can't possibly justify the ecological expense of selling a car that sees under 5000 km/year of usage, but misaligned government incentives increasingly push me to.

[0] https://en.wikipedia.org/wiki/English_units#Length [1] https://translate.google.com/translate?sl=auto&tl=en&u=https...

In proper US customary units, that's 62 square mil.

The Chevy Volt only gets about 90 square mil on its generator, but its battery is more like 33 square mil-e.

Why did you say square miles? What an odd measurement to use.

That's 62 miles per gallon and 90 miles per gallon.

Why use area as a measurement and not distance?

OP is doing a bit, but it’s because a volume (liters) divided by a distance (km) reduces to an area.

You can think of it as the cross-sectional area of a hypothetical straw sucking up fuel from a continuous trough set into the roadway.

Square mil, and square mil-e[quivalent], for the battery-only efficiency, not miles.

When you have a volume-per-distance measurement, such as liters/km, you can cancel units to get an area.

The square mil -- a mil is 1/1000 of an inch, usually used in machining parts -- is the US customary unit which is best suited to the magnitude; 62 square mil is so much nicer than 0.04 square millimeters or 40000 square micrometers.

That went securely over top of my head.

I have a regular, petrol powered SUV and regularly get 13l/100km. If I go granny mode I can get it down to 10l or less. Now I don't feel so bad for not hitting these magical consumption claims. It has 380hp (280kw) and wants to be driven as such.

They did some research in the UK (can't find the BBC article right now, it was maybe 2 months ago) and by huge margins most folks drove hybrid in most eco-unfriendly way possible (little to no charging due to poor infrastructure and costs). So hybrids ended up as biggest polluting passenger cars in real world, when averaged.

I can imagine ie some nordic countries could have better stats though.

>So hybrids ended up as biggest polluting passenger cars in real world, when averaged.

like the article itself, that statement is subject to a lot of conditions to the extent that it is meaningless without clearly stating all those conditions. For example, even without charging i average 48mpg on the previous gen Prius Plugin (and i do drive 85-90 on 237 - better aerodynamics results in very good mileage even at speed). You need very-very special setup, far-far from real world, for that to become "biggest polluting" .

There's a difference between something like a Prius+ and the PHEVs mentioned in the article though: the BMW X5, Volvo XC60 and Mitsubishi Outlander are big, heavy SUVs, it's hardly surprising that they have poor emissions.

if the implementation isn't screwed (sounds like a big if), they would normally have better emissions than their non-hybrid variants due to regenerative breaking (especially for big heavy cars) and better ICE burning modes (even if you use the same ICE, and much more improvement can be gained by making an ICE optimized for hybrid application). If the article is anywhere close to truth, then it can only be explained by the bad implementation - may be they moved the freed diesel engineers to do the hybrids after the dieselgate :)

Recently walking a dog waiting for the light i saw/heard a Volvo XC90 hybrid doing ICE start from the red-light stop - the ICE started a moment before the car started to move - it did cross my mind back then that such start of engine would [unnecessary] burn a lot - ie. my Prius starts moving on pure electric with the ICE kicking, if/when needed, some moments later, much smoother, better torque and better efficiency. The performance-wise the XC90 had a regular start, far from anything fancy, and anyway large starting ICE wouldn't produce much performance while starting (and waiting for it to spin from the 0 in order to get some performance would eat the time thus killing that performance), so why would they do that ?

They have to carry the batteries around which are heavy.

starting up an engine isn't nearly as "expensive" as people tend to think. engineering explained did a video on this, concluding that a warm start in a typical four cylinder engine uses about as much fuel as idling the same engine for only ~7 seconds. [0] kinda makes sense, since this is the whole motivation for start/stop systems in the first place.

not covered in the video, but IIRC cold starts use quite a bit more fuel since the engine needs to run rich for a few minutes while it warms up.

[0] https://www.youtube.com/watch?v=dFImHhNwbJo

> i average 48mpg on the previous gen Prius Plugin

Man, I did 46 mpg with a VW Passat in 2018 (UK gallons tho)... Stats like these are disappointing.

why? hybrid brings efficiency of the gas engine to that of the diesel (and better than that in the city) while being much cleaner. 15-20 years ago (the first years after coming from Russia where diesel was definitely a better option back then - and my father had diesel VW Passat there at the time :) i thought that the diesel was the way to go and was disappointed at California for the "anti-diesel" law, and only later understood that it was a right thing to do.

Also, people get confused with the efficiency of diesels, comparing MPG between petrol and diesel, when they're liquids with different densitites and carbon contents.

I just expected more by what was effectively the hybrid gold-standard (the Prius). My Passat was a regular diesel with some tweaks (VW called it "bluemotion"), thinking it got so close to the average hybrid efficiency made me slightly sad for a minute. But it's not important anyway, hopefully we're rapidly approaching an electric-first setup and that's what matters.

You should really mention that it's diesel in a comparison like this. Diesels produce significantly more air pollution (particulary nasties like NOx) than similar gas/petrol engines.

one thing to note is that there's a reason electric cars have lower range on the highway and gas cars have higher range.

first thing to note: the faster you guy, the less efficient you can be (air resistance effects you to square I of speed I believe). So this explains, why electric cars get a lower range, the faster you guy, the more air resistance they have to overcome vs local driving with less resistance.

but what about gass engines. This is simple: gas engines are inefficient. they can't be configured to produce exactly as much energy as needed (as opposed to a drawing from a battery). Therefore, at lower speeds, they are producing much more energy than is needed and it gets wasted. at higher speeds, even though they have to overcome the same amount of more resistance, much less energy is being wasted as more is needed. This has gone into why so much tech has gone into trying to make gas engines more efficient, from the prius's hybrid system, to stop/start to deactivating cylinders and on and on.

how well did your passat do on local driving? my guess perhaps 2/3 of that number?

If I remember correctly a lot of that came from fleet cars. Often the drivers never got as far as unwrapping the charging cable. They weren't paying for the fuel so they didn't care or they never had somewhere to plug in.

This isn't really the drivers' fault though. When this happens, it's usually because the company is willing to reimburse them for fuel but not for electricity.

This lines up perfectly with my predictions for the future of UK roads - they will be filled with leased, oversized hybrid SUVs, driven by people who care about nothing except getting to their destination.

These vehicles will be hybrids, because it's now almost impossible to sell a new ICE only car in Europe/the UK. Following from that, they will be SUV-sized, because hybrids add lots of extra drivetrain components and weight. Also following from that, they will be leased, because of the increased cost.

I am particularly aggrieved about this, because I generally cycle everywhere I can, and despise this new "green" future for motoring. I also tend to buy 10 year old second hand cars, which was already getting hard enough with all of the extra electronics on newer cars. The idea of buying a 10 year old, ex-lease, completely thrashed, hybrid SUV - well. I'd rather walk.

>>Following from that, they will be SUV-sized, because hybrids add lots of extra drivetrain components and weight

Not sure if I follow this, Golf GTe, Audi A3 e-tron and similar are hybrids and not exactly SUV-sized

Just for fun:

https://www.carsized.com/en/cars/compare/volkswagen-golf-201...

Edit: The current Mk 5 VW Polo is quite a bit bigger than the original Mk1 Golf.

Why compare it to the Mk1? How does the modern gas version compare to the Mk1?

I'm comparing the modern Mk 5 Polo, which is supposed to be a small city car, to the original Golf, which is a family hatchback, to point out the ever-increasing size of vehicles. The modern Golf (including the electric/hybrid variant) is about the same size as the Nissan Juke, which is a smallish SUV.

On-board computers that send data home about how many times they have been refuelled and charged? I suppose it might not go down well with car buyers, though.

I do think that a consumption-based tax can be implemented for PHEV's using the data from the onboard computer. When you pay your annual tax or go for the inspection, you either take a readout of the car's consumption metrics from the OBC or have the shop/DMV do it.

Then you charge tax based on the consumption. Thus, someone who used electric a lot gets charged less than someone who didn't, which is what the incentives for PHEV's are supposed to encourage anyway.

And my guess there will be people who sell black marker services, or perhaps it will just be open internet knowledge, and we will see people jailbreaking their cars to alter the displayed mileage driven to cheat what they have to pay.

If you think all laws will be broken anyway, what's the point of having laws?

What an overcomplicated way of doing what would be achieved very simply by raising petrol fuel taxes by a few cents?

If you want to penalise carbon emission, tax carbon, not cars.

Raising taxes on a fuel is not as effective, first because its harder to get through to the consumers - they don't care because the tax would be pennies on the liter/gallon, and people are used to prices going up and down anyway. Secondly because such an annual tax would hurt the wallet more - paying $100 once hurts more than paying $1 a hundred times with every fill-up.

Yes it is overcomplicated but it is a solution that targets the core of the problem - that people are not charging their PHEV's enough.

That depends on the tax rate. The >$4/gallon price delta between most of the EU and the US is entirely taxes. That's quite a bit more significant than pennies on the gallon...

I mean the marginal tax rate increase from current levels. Unless you mean gasoline taxes should be $4+ additional per gallon compared to what they are now.

Raising fuel taxes to EU levels would not be enough, but it would be a significant start towards environmental improvement, and not necessarily bad for the economy.

In a hypothetical future that is where people realise there is only one earth and some compensations are provided for the economically weaker whose livelihood suddenly gets threatened by these changes.

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