Unless Toyota knows something, I don't know, I would think that the decided advantage is to the car with the larger battery, smaller ICE, and less complicated drive line. I still believe a BEV, with a microcomputer controlled portable generator, perhaps on a trailer, as a range extender for long trips (600miles), would fit most of our drive cycles, especially if there is an abundance of charge stations along the way to help offset the liquid fuel usage. For short to medium distances, the generator and its weight and drag wouldn't be needed. Think about how much lighter the car would be and how much more space would be available without the need of the inefficient ICE and its associated drive mechanics.

If everyone started driving around with little trailers we would have to redo all the parking lots in the US.

This is very puzzling, to say the least, and Toyota is making a very big bet on longer than necessary odds. I can't figure out why they seem to be so anti-series hybrid. Could it be that they've convinced themselves that consumers won't buy them? If that's it, I'm convinced they're wrong, and the market will change their mind in due time, the hard way.

@ Ziv -

I'd be careful about claiming that Toyota will be playing catch-up with GM on plug-in hybrids for a number of years. The regular Prius is shipping today whereas the Volt is vaporware. An affordable vehicle with a 16kWh Li-ion battery pack is a tall order.

The Japanese always prefer incremental improvement over revolutionary changes, because the engineering risk is much lower. That said, Toyota's preferred battery manufacturer, Panasonic, hasn't come up with sufficiently safe Li-ion batteries yet so they have to keep using proven NiMH technology and spin that as a good thing. In practical terms, though, an 8 mile range on grid electricity is too little to be worthwhile. You'll almost always have to fire up the ICE at some point during your trip and, heating the block and oil guzzles gas.

The external socket is still useful if it can be used in reverse to run your home during a power outage or, for running mobile electrical equipment where there is no grid access (e.g. lights on a camping trip, power tools when clearing brush on your land etc.) However, you don't really need a secondary battery for that. If you leave the key in the ignition, the engine should just fire up if your plug-out power demand can no longer be met by the battery without reducing its life expectancy.

What is true is that Toyota's compound hybrid transmission is a more efficient drivetrain than GM's purely serial hybrid with battery buffer can ever hope to be. The genset will be running efficiently but that won't fully compensate for the high drivetrain losses. Ergo, once you get beyond the range covered by grid electricity, the Volt will actually be a wee bit of a gas hog.

Lad, thanks for the link, I think Lutz said a lot of interesting things but the one that stood out the most to me is that he said they would build it on time if there were no unforseen problems, or words to that effect. It just seems like he would be more guardedly optimistic, and would be stressing the game changing nature of the switch to primarily electric energy more, if GM really thinks they can pull this off within 3 years.
Rafael, I think I understand what you are saying about Toyota having the Prius in hand, and the Volt is still in the bush, but Toyota doesn't seem to be building/designing anything that would compete with the Volt in a meaningful way. Unless they spring something in Frankfort, it sounds like they are not going to be making a real Plugin vehicle in the next few years. 8 miles range or 10, or 12, just don't mean anything. If GM can build a car with an electric only range of 40 miles, it won't matter that the Prius gets 70mpg and the Volt gets 'only' 50mpg after the first 40 miles when the range extender kicks in, because it won't happen frequently enough for the Volt be using much gasoline, anyway.
Finally, Lutz has stated that they will have a functioning prototype early next year, so if GM can put the car on the road in some form within a few months, maybe they actually will sell 60,000 of them in 2010 as Bloomberg claims they are working towards.
I have to admit that I am incredibly biased, I really want the Volt to work and my enthusiasm for it has me both more optimistic and pessimistic at the same time. If they build this type of car it could change the world in a relatively short period of time. We have a world economy based on cheap oil, which is now not so cheap, supplied increasingly by nations that we really shouldn't be enriching, i.e. Saudi Arabia, Russia, Venezuela, Iran... If the automotive portion of the global oil demand began to decline as cars increasingly use electricity instead of gasoline, the impact would be huge, and it wouldn't take long for the changes to be felt.
We are at or near peak oil production, and the only thing that can stave off relatively rapid rises in oil prices is a reduction in demand. We can't increase supply so we need, absolutely, to reduce demand.

I would expect that GM is doing their typical boast and botch approach. You can get 40 miles all electric on a prius today by reprogramming it, but it will definately cause battery pack replacement much, much sooner. the deeper you draw the less life they have. Chevy can assume the battery tech will be much better by then, or maybe they are expecting the Volt to be like the Vega, a disposable car that people wont mind tossing in three years when the battery is toast.

The rationale, outlined by Toyota Executive Vice President Kazuo Okamoto in a presentation on the company’s technology strategies to investors in Tokyo on 3 Sep [...]

Toyota investors have been hearing about the Volt for a while now, and likely want to know why GM appears to be stealing a march on them. Toyota needs to downplay the Volt as much as possible to keep the investors quiet while (a) hoping the Volt fails, and (b) kicking their engineering into high gear to beat it. The fact that they're pushing their 8-mile Prius as a better solution suggests that GM may have caught them with their pants down.

The series is a better approach it seems.

I wonder if Toyota simply doesn't want to ditch technology that they have a significant investment and lead in?

Either way, GM has a lot to prove. I question people saying it's total vaporware. GM can't afford not to release this car, it's the best PR they've had in years.

8 miles range on the plug, that pitiful! Need at least 40 miles which is what the volt is intended to have. To get that range you need a bigger battery and powerful electric motors, if your motor(s) can push you around with good acceleration there is no need for an engine drive transmission: a little engine generator plus larger electric motor(s) is less expensive compared to a big engine with transmission and generator plus larger electric motor(s). Sure your long range driving might be less efficient in serial mode then a parallel setup, but now you’ll have enough space and money left over for bigger batteries and greater plug in range.

Toyota has already slapped together and are testing a PHEV Prius with a range of 8 miles. I'm not sure what the extra cost would be, but doubling the pack size, modifying the ECU/s, and slapping an inverter in there can't be that expensive. GM otoh has nothing more than a mockup with a few lead acid batteries, an electric motor, and a laundry detergent bucket...
http://sirymarketing.blogspot.com/2007/03/more-on-volt.html

Provided affordable and suitable batteries do become available in a few years, I don't see why Toyota wouldn't have access to them as well and upgrade their range accordingly. Unless there's some back room government of corporate advantage GM has that Toyota doesn't?

Considering that the total typical mid-size drive train weight would be almost the same for both technologies, i.e.:

1) Parallel = 50 Kg bat + 450 Kg mech = 500 Kg

2) Series = 300 Kg bat + 175 Kg mech = 525 Kg.

the long distance highway mpg should be about the same. However, the short distance (40 miles) mpg should be much better with the series setup (no gas required) unless the parallel unit uses the same 300 Kg battery pack. Adding another 250Kg would make the latter much heavier and make highway mpg even worse.

A series 40+ miles PHEV with the smallest, very light E-flex onboard genset seems to be best way to go.

Aussie: I guess that would depend on the ratio of up to down and how efficient the regen would be on the down. I would hope that the Volt would have a "long range" mode that would tell the genset to start running right from the start of the trip.