There seems to be a common idea that the only way a PHEV is a beneift is with a EV Mode.

While an EV mode has benefits and there is no need for me to go over those which others have done many other times... an EV-Mode is not the only way a PHEV is a benefit.

The issue coould come up because if you are only in EV mode all the time, the gasoline enegine / generator is just dead weight , and cost ... once you are in HEV mode additional batteries for the extended EV mode are now just dead weight.

If you actually run a PHEV into the HEV mode on any kind of a regular basis or for a long enough period of time a pure EV-Mode might not be the best use of that Plug in energy.

In a convenstional PHEV / REEV with an EV mode you use up the Plug in energy first... than the car reverts back to HEV operation and the additional PHEV / REEV batteries are just dead weight.

If however, the Plug in Energy were used to assit the ICE and keep the efficiency better you would result in more useful work extracted from each mL of fuel supplied.

If you get ~50 EV miles and then ~50 MPG for ~50 Miles the conventional PHEV with EV mode averaged ~100MPG, over that ~100 miles... which is good ... but if an assist PHEV can get over 150MPG over 200Miles that is better for long distance driving.

http://www.solarvan.co.uk/

Above is a link to a guy in the UK who did just that... by using a ~6kwh PHEV battery with his Honda IMA Gen-1 Insight he was able to use it as an assited PHEV and get that ~150 MPG over the ~200 Miles.

For short trips and sense some ~80% of the drivers in the US drive less than ~50 Miles a day the EV mode still has some major benefits ... but I forsee a better option .... eventually.

Determine which would be a better benefit for that drive... to use up the Plug in power all in the EV mode ... or to spread it out in a longer applied Assist type mode to keep the ICE running as efficiently as possible... the option and flexibilty would be better than strictly limited to either.

The side benefit of an assist using PHEV option is that it can boost the fuel to the wheel efficiency of a PHEV / REEV.... many REEVs and PHEVs introduce additional losses when they introduce additional steps ... ICE to Generator to control electronics to batteries back out of batteries back to control electronics back to motor back to mechancial power... but systems like the IMA system with a PHEV could potentially be better as they do not have as many losses in conversions ... and with the additional plug in power an IMA like system can still keep the ICE up in an efficient range of operation without those additional steps of conversion losses.

... well there is my thought anyway... :)

As an owner of a 2005 Prius PHEV, I can say I get more utility day-to-day from the hybrid mode getting an average of 70 mpg on my 76 mile per day commute. Surely on the weekend I can do local short trips in EV mode, but in my case these trips are the exception, and not the norm.

I will say that my PHEV is a 10kw Thundersky LiFePO4 pack, and not your traditional PHEV pack. I upgraded from 2 kw PbA batts that were getting me roughly 60 mpg blended as they could only help for about half the trip and weighed an additional 80 lbs over the TS pack.

I am more of a enthusist myself... my own plans for adding PHEV power to my 2000 model year Honda Insight... has had lots of set backs... delays ... complications ....etc.... most recently , I'm a bit stumbed by my apartment not allowing or budging on a plug ... so I might end up moving.

I think we will see more of the blended mode PHEVs over time ... there are several situtations in which it is a more net efficient use of total energy.

Sometimes , people get stuck thinking in the box... but it will work out.