I've blogged about this topic often before. Replacing the energy we currently use in terms of gasoline is not going to be any easy trick. It will involve generating at least 1400 GW (yes, gigawatts) of electricity. Solar panels on your roof and windmill farms simply are not going to cut it, as far as generating that sort of energy goes. Until we can produce that sort of energy, we will be dependent on oil.
Furthermore, we can't simply become more efficient until we stop needing that energy. The productivity of modern civilization, our freedom from medieval grinding poverty, and our ability to sustain our population is directly proportional to the extent which we can get our machines to do work for us. Machines don't work if they don't have energy, and there are sharp diminishing returns in terms of efficiency for increasing device complexity and cost. The bare minimum energy to perform a task (move material across the country, for example) will always be there, and the thermodynamic limits of efficiency aren't going to allow us much leeway in that department either. Trying to improve efficiency is like looking for loose change under your sofa to make your student loan payments.
Whatever form the storage method for the energy takes, hydrogen, boron-hydrides (one of my favorites), or batteries, the energy itself must be supplied. Currently, I don't think there are many alternatives to oil other than massive nuclear and hydroelectric generation.
