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An idling gas engine may be annoyingly loud, but that’s the price you pay for having WAY less torque available at a standstill.
3 points
I think there was a Renault that worked like this. I think the main issue is that you need a decently sized battery that can supply enough power or else the ICE needs to start every time you hit the gas pedal like was the case with the older Prius models and then you might as well connect it to the wheels and you can have a smaller electric motor.
But batteries keep improving and you can pull more power per kWh now. Maybe with solid state batteries this power train could become the more affordable option.