Some places claim the most fuel efficient vehicles are about 40% (again, on a good day in testing conditions).
EVs on the other hand are up around 87% or higher.
You can make it a bit more efficient by optimizing an engine for a specific singular output, sometimes up to 50% I think is what nissan claims. One automaker, I forget who, was researching doing a hybrid drive train like the volt had, but where the engine could run in that one single speed and charge a battery.
Seems a lot more complicated than just electrifying the system, but I'm not a auto researcher.
Nissan's PR about it: https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
Where the challenge comes for smaller vehicles, is the more power you are trying to give, the more you have to build everything up; not just the engine but whatever that engine is inputting into, also trains have somewhat more predictable speed profiles over a trip vs a car.
This is why some manufacturers have vehicles that are PHEVS but really BEVs with an 'oh crap' extender that can struggle to keep up a good grade.
I gotta give TRD/Toyota/Ford credit, the HSD style drive train does work around a lot of this stuff for PHEVS; in lockup mode you have a 1:1 ratio with minimal losses and at that point it's up to the ability of the engine to adjust profile.
Works very well in practice, and far simpler than the setups of others.
Automotive motor controllers now use similar technology, but the locomotives had it first.
[1] https://en.wikipedia.org/wiki/Diesel–electric_powertrain
Fortunately.[1][2] British Rail tried in the 1950s. Four 12-cylinder Diesel engines driving the the wheels through three differentials and four hydraulic clutches. The engines were geared such that the speeds added. As speed increased, more engines were turned on. Since startup only used one engine, starting pull was rather low for the engine power installed.
Only one was ever built.
Not sure if this is what you're thinking of but Honda's eHEV platform drives the wheels with an electric motor and small battery†, with the engine kicking in as needed to generate current and to charge the battery (as well as regen).
†Until you get to high speeds, at which point a clutch engages and the engine drives the wheels directly, via a single fixed gear.
But if you drive like a leadfoot that doesn't really work cuz then usually the hybrid systems fall back on the gasoline engine for additional torque and it goes to the normal gas cycle when it does that and you lose the efficiency
Coal plants are about 33% efficient and natural gas plants are about 45%.
If you want to say that this factor doesn't count: In what sense should the oft-quoted factor in the final step count? (That is, the loss in converting from petrol to rotational motion in an ICE, or from electric potential to rotational motion in an EV.) I think the only real utility that number has is in estimating the total amount of stored energy in a typical car of each type -- this could be used to estimate the amount of damage that would be caused by the vehicle catching on fire.
Other claims strike me as meaningless.
We care about the efficiency of converting resources we have a limited amount of, sunlight is unlimited on humanity's scale, so is wind, but how much solar or wind power we can extract from them and transmit has constraints and that is the step where we should start caring about efficiency