There's always bio-diesel, of course.

Unfortunately several "studies" indicate that the fertilizer to grow the corn required to make the biodiesel actually consumes more petroleum than would be required to make a quantity of petro-diesel equal to what the corn will produce. And growing corn requires enormous amounts of water - compared to other crops, and can't be grown productively on much of the available "farmland" for that reason.

Probably the main "wild card" in the hybrid game is the performance of the batteries being used in most of them. (Performance includes cost and useful life, of course.) There's little actual experience with any of them in the specific kinds of service required, but most agree that "better" is needed.

Most of the "informed opinion" I've seen indicates that current hybrids are most useful for those who make mostly short distance use, with about 40 miles (64 km) per day being the limit of really effective use. There are several choices of hybrids, with slightly different range capabilities, of course; but the intended use has a strong effect on how much one saves. Efficiently doesn't terminate abruptly if one exceeds the "magic numbers," but does tend to wither away as daily mileage increases.

My "home town" has bragged about a report showing that it ranked number 10 (of 500 medium to large) US cities for "shortest average daily commute to work" at 38.7 miles (round trip). Even those commuting "only" 39 miles for work are likely to run an errand or two almost daily, so even here average miles driven daily would likely be (much) over 40 miles. The currently available hybrids seem ill-suited to most US drivers' usage on the basis of useful range.

(Note also that in many of the US places where the commuting distance is less than here no kind of personal vehicle is really useful since there's no place to park at most destinations.)

The progress being made is encouraging, but one must have the situation that fits the available performance before it becomes an economic advantage to have a hybrid. Performance is good enough for many people to use a hybrid, but for most drivers here the "just because I want one" factor has to weigh in pretty strongly.

John