Ultimately, the most straightforward source of power for transportation is sunlight converted to electricity. However, there are two major problems with current technology. One, we cannot convert the sunlight to electricity efficiently enough to replace fossil fuels and two, batteries that could conceivably store enough power for cars are way too expensive. While it's good to see progress being made in both of these areas, it will be at least 5 years before some of the recent breakthroughs reach the automobile industry.
Plug-in hybrid cars fill that 5 or more year gap in three important ways.
The immediate benefit is that the fossil fuel engine (normally a gasoline powered internal combustion engine (ICE) in the US) can be optimized for a narrower range of RPMs while the much more efficient electric power source can take up the load where needed. You don't hear much about it but electric motors are up to three times as efficient as the same power producing ICE. So, once we have converted a fuel source to electricity, converting the electricity to mechanical work is very efficient (obviously, it is the creation and storage of the electricity where we lack efficiency).
Secondly, hybrids allow us to realize better efficiency in the automobile without needing a whole new fuel distribution system. Yes, this is a stop-gap measure, but it is something that we can do now for pretty much the same cost (spending money up front for a hybrid instead of for gas over the life of the car). And it has the added benefit of reducing our dependency on oil immediately.
Lastly, but very very important, a plug-in hybrid will allow us to leverage both electricity from the grid and improving solar electricity conversion over the coming years. It is very likely that within 5 years home solar (and wind) electricity production will become affordable. At some point, not only will you be able create your own home electricity but (if you install enough power generation) you will be able to charge up your plug-in hybrid as well for no additional cost. Sized correctly, you could eliminate the need for gasoline for local driving. How much do you pay for gas annually? Right now, I pay more than $6,000 per year for local driving (two cars). A rough estimate of the equivalent cost for electricity at the current high local utility cost is $4,000 annually. So, without solar power generation I could save $2,000 per year if my cars could cruise around town on battery power. If I were to create enough of my own electricity at the house, I could save up to the full $6,000 cost for local driving, as well as the electricity the house uses (around $1,800 per year). That means over the life of the power system (assume 10 years), I could save $78,000, which would more than cover the cost of the installation even at today's prices (and this assumes the cost of energy doesn't go up during that 10 years).
To conclude, coupling plug-in hybrids with home electricity generation is a revolution in the making. Is this unrealistic? I don't think so. I plan to use this blog to search for and record the necessary things to make this happen. My goal is to replace both cars with plug-in hybrids within 5 years, and to install solar (and possibly wind) electricity generation over the same 5 years.