Gremban, an electrical engineer and committed environmentalist, spent several months and $3,000 tinkering with his car.
Like all hybrids, his Prius increases fuel efficiency by harnessing small amounts of electricity generated during braking and coasting. The extra batteries let him store extra power by plugging the car into a wall outlet at his home in this San Francisco suburb -- all for about a quarter.
He's part of a small but growing movement. "Plug-in" hybrids aren't yet cost-efficient, but some of the dozen known experimental models have gotten up to 250 mpg.
Nicole and I figured up (before gas got above $2) that it would take about 10 years of using a hybrid to start making money from using it (as in it would be cheaper after 10yrs to buy a hybrid model instead of a normal car, for the same model). If the efficiency can be bumped up to even half this for normal cars, and prices decline or even hold for the cars, soon not getting a hybrid car would be stupid. Huzzah!