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Comment by alostpuppy | Hacker News Reader

Out of curiosity, What is the wh/kg for petrol?

Wikipedia says 13000 Wh/kg, but you have to keep in mind that due to physics, wear considerations, and emissions regulation, most cars are only 20-40% efficient. At a 20% efficiency, that's 2600 Wh/kg. This is further constrained by gear ratios, meaning not all power is available at all times.

Exactly. Gasoline is much, much more energy dense than Li-Ion batteries, but in terms of dollars per mile, an electric car is 2x-4x cheaper to drive than an ICE car. That's because an internal combustion engine wastes the majority of gasoline's energy as heat, while electric motors use most of the battery's energy to move the car.

> an electric car is 2x-4x cheaper to drive than an ICE car

It hugely depends on the cost of electricity. Last year some European countries (Netherlands IIRC) had those so high, that it was actually more expensive to drive EV than ICE.

You can optimize this with the right electricity contract. Time of day pricing ("dynamisch tarief" in the Netherlands) combined with charging during the cheapest times can make a big difference. And as a bonus to society, you help to balance the grid.

> That's because an internal combustion engine wastes the majority of gasoline's energy as heat, while electric motors use most of the battery's energy to move the car.

I guess that depends on your perspective and/or where you live.

I rented a Tesla in December once and was freezing the whole drive. A gasoline engine generates extra heat you can use to heat the cabin, whereas an electric car needs extra heaters (which IME weren’t working that well in that old Model S)

Heating the cabin was a known problem with older Teslas, especially because resistive heating reduced range significantly. Newer Teslas use heat pumps which are much more efficient.

> This is further constrained by gear ratios, meaning not all power is available at all times.

CVTs enter the chat.

> At a 20% efficiency, that's 2600 Wh/kg.

Hybrids do better, of course.

CVTs enter the chat, but it's mostly to ask when they'll be replaced so you can use them again.

(I don't remember details, but we decided to specifically avoid cars with CVTs because of reliability issues. Sure enough, the only person I know with a CVT is having belt slipping issues. Seems like certain manufacturers were switching back to dual clutch arrangements)

Drove a Suvaru with CVT for 100k km. Never had any issue. Never heard of anyone having issues with CVT (from Subaru).

My understanding is that the Nissan CVTs weren't outfitted with a large enough radiator, and that the resulting overheating is what tended to kill them. I don't think there's anything inherent about their design besides the insufficiently large radiator that would cause failures more frequently than non-CVTs.

https://www.google.com/search?q=Wh%2Fkg%20of%20gasoline

Fuel Energy by mass (Wh/kg) Energy by volume (Wh/l)

Diesel fuel 12,700 10,700

Gasoline 12,200 9,700

Natural gas (250 bar) 12,100 3,100

Body fat 10,500 9,700

About 12,000

https://batteryuniversity.com/article/bu-1007-net-calorific-...

Obligatory XKCD: https://xkcd.com/1162/

Which works out at ~21,111,111,111 Wh/kg

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