Correct me if I am wrong but I think there is an increase in FE even without plugging in due to the electric motor being vastly more efficient than the ICE. As such when the battery pack is depleted and needs to be recharged by the ICE it is still more efficient than the ICE alone. The energy to recharge and drive in EVmode or assisted ICE is overall lower than ICE alone. I see when on the freeway that the ICE and then the ICE and electric motor pulse together off and on. This gives more FE and adds power too. When the assist is pulsing the FE bar jumps about 10 MPG and when it stops the FE bar drops about 7 MPG. This drop is due to the loss of the assist and the load to recharge the batteries too. Since the electric motor is about 2.5-3 times more efficient it adds MPG to the total.

While it is true that plugging in would be even more efficient going hybrid is better than ICE alone.

The best FE seems to be to determine the total daily use without needing to plug in until back at home and design the FEH to deliver within this determination. This would be the absolute best. BUT the design would be different for everyone so there needs to be a compromise that fits the AVERAGE drivers needs. I think this is where the 20-30 miles in EV only mode is coming from. If you could drive to work in EV only and then plug in at work you could effectively double the range with zero added cost beyond the cost of the electricity and some wear and tear on the batteries and mechanicals.

This brings up an interesting thought. If you worked 10 miles from home and could plug in you would still be very FE AND could keep the plug in modification at an overall lower cost. Hence for the 80% yearly use, figured on back and forth to work, it would do all you needed in EV mode and this would be less expensive in the near term. As battery and plug in mods come down in price then the miles in EV mode could extend. This would add others into the fold and make owning an PHEV more palatable.

I think all here agree that, as it is, the EV mode is at best a quiet drive in the parking lot and down a short side street. Give us 10 miles and 40-45 miles per hour EV mode and we now have a solid EV that delivers some valuable daily use. A little faster and farther makes all the difference in the world.

I want mine yesterday. But not if it is going to cost as much as double what an FEH costs now. This is not viable IMO.