You can also have a much smaller engine for a much bigger car, since you only need to cover average not peak power usage.
You also in most designs eliminate the gearbox.
I don't know about the whole world, but in both the US and Europe nearly half of the hybrids on the road are from Toyota, so unless nearly everything else is two parallel drive chains linked with clutches whatever Toyota does is the more common type.
Toyota uses a series-parallel system that works by having a planetary gear system that connects the ICE, a large electric motor, a small electric motor, and a drive shaft all together.
The planetary gear system functions as a power splitting device and a continuously variable transmission. It lets them direct power flow in a bunch of different ways. Here's a summary based on Wikipedia. (MB == the bigger battery, 12V == the regular 12V batter, ICE == the ICE engine, MG1 == the smaller electric motor, MG2 == the larger electric motor):
• Aux power: MB -> DC/DC converter -> 12V
• Charge: ICE -> MG1 -> MB
• EV drive: MB -> MG2 -> wheels
• Moderate acceleration: ICE -> wheels, ICE -> MG1 -> MG2 -> wheels
• Highway: ICE -> wheels, ICE -> MG1 -> MB
• Heavy power, such as on steep hills: ICE -> wheels, ICE -> MG1 -> MB, ICE -> MG1 -> MG2 -> wheels
• Max power: ICE -> wheels, ICE -> MG1 -> MG2 -> wheels, MB -> MG2 -> wheels
• Regenerative braking: wheels -> MG2 -> MB
• B-mode braking: Wheels -> MG2 -> MB, Wheels -> MG1 -> ICE
This is a big part of why Toyota hybrids are at the top of reliability rankings. Compared to a pure ICE they replace the clutch, the transmission, the starter motor, the alternator, the reverse gear set, and the flywheel with the planetary gear power splitting device. the two electric motors, and electronics. The power splitting device has very few movings parts--just the gears themselves, a pawl that can mechanically lock the gears when parked, and fluid pumps. The gears only move by rotating, unlike in a conventional transmission where they also change position. This makes their hybrids mechanically much simpler than a pure ICE.
Data collected across 600.000 vehicles in Europe show that most people don't and that emissions are just a smidge under typical ICE vehicles. If you factor in the high emissions produced during battery productions it looks to be an overall bad package.
The idea itself is certainly good but the real world simply doesn't show it.
https://www.evshift.com/368695/do-people-actually-charge-the...
For example, the sluggish 0-60 is due to the design being unable to get all the power from the engine to the wheels at slow speeds, due to the electrical path through the CVT gearbox being too small.
The funny noises when going down really big hills are due to the system having no way to dump excess energy after the battery is fully charged and being forced to rev the engine at 5000 rpm with no fuel to waste some.
The slow throttle response is due to the engine always running at 80% throttle for efficiency, which means if you suddenly need more power you can only quickly get an additional 20% before waiting for the rpm to slowly rise and give lots of power in a few seconds.
EV's do have similar design limitations (drive on a racetrack and you'll need to let the hardware cool between laps), but they seem easier to overcome by simply sizing the system slightly bigger to hide the limits.
