The amount of energy that goes into making ethanol far exceeds the amount of energy you can extract just by burning the entire plant. Electricity produced at reasonable scales extracts 1/2 of the energy from combustion. The waste heat is often used for heating either municipalities or industrial chemical processes. Thermodynamically, you do not get better efficiency than 50%. Once its converted to electeicity, the energy is delivered to your battery at nearly 100% (yes i know its less, but for argument's sake it might as well be). Lithium ion batteries, a true modern miracle, have very very low energy loss during charging, storage and discharge.
With alcohol, if you were 1% efficient you'd be lucky; this if you include solar energy conversion to plant sugars, chemical spraying, harvesting, drying, mashing, distilling and delivery.