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Comment by dieortin | Hacker News Reader

Very impressive for a combustion engine, but still way worse than the ~90% efficiency of a battery electric car

If your electricity comes from hydro, solar, wind - yes. If your electricity comes from fossil fuels - best power plant efficiency 60% - then not really. In US fossil fuels generate 60% of all the electricity.

If you’re going to use the “well to wheels” number for electricity then you should do the same for ICE vehicles.

Also, 40% of U.S. power generation is renewable? Impressive!

90% * 60% = 54%, which is still way better than the most efficient internal combustion engines. So even in that case an EV is still better. Plus, it gets greener when the grid gets greener.

I'm not super concerned about green energy, but i put solar panels on my roof and charge an ev because it's incredibly practical and a much better experience than the status quo.

If your power comes from fossils it's already been shipped half way around the world and refined, so that should be included in any efficiency calculation.

Much less than 100% of electricity is... still more efficient than ICE? I don't see how that changes things.

US electricity averages 384g CO2/kWh, so EVs emit 100-130g/mile, equivalent to 90-110mpg. And that improves year on year, while an ICE is at best as efficient as when it was produced

while a very important aspect (and you're right that EV are more and more better on that), that isn't strictly thermodynamic efficiency you're talking about. For example, natural gas is a major fuel for electricity generation and, even at the same efficiency, it produces less CO2/KWh than say gasoline.

Methane (natural gas) is a powerful greenhouse gas, much more insulating that CO2. Leakage of methane during production and transport will have a huge impact over the short term (next 50 years). It is actually way worse than gasoline or coal for that reason.

By the time all the CH4 we are dumping into the atmosphere has broken down (half life ~12 years) we will have pushed global temperatures much higher.

Efficiency, output per input, is only relevant for similar inputs. An ICE being more efficient means proportionally lower costs and emissions, but like you said, an electric drivetrain being 90% efficient is less informative than a well-to-wheel comparison.

Similarly, I think it's unhelpful to just expand it to primary energy. What's the efficiency of a wind turbine? In 50 countries already, a 100% efficient ICE would emit more than an EV! The reason for efficiency here was costs and emissions, so compare those.

50% power efficiency is for burning gasoline, not oil. Once accounting for energy spent on refining oil into modern gasoline it is like 35%. And with that it will consume less oil to burn it on modern power plant approaching 50% efficiency even accounting for refinery losses and then use that in EV.

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