Yes, because it's an Atkinson cycle engine so the engine efficiency is much better, and also because normal car alternators are absurdly inefficient; about 50%

Yes, because it's an Atkinson cycle engine so the engine efficiency is much better, and also because normal car alternators are absurdly inefficient; about 50% or so, I think. The Prius's motor-generator is more like 90%+ efficient. The Prius's motor-generator might not be able to run at 100% duty cycle, but they're tens of kilowatts max output so you'd need a pretty big load. Many car alternators also won't run at full load for very long, and can only do about 2kW, so definitely a risk. Either the windings overheat, or the voltage regulator will. They're sometimes thermally regulated, but not always. You can sort of band-aid it with forced cooling to supplement the centrifugal fan on them.