[mjard]

Volumetric energy density. Either you'd fill up more often or dedicate more vehicle space to energy storage.

Diesel: 10,722.2 W hours / Liter

Gasoline: 9,500.0 W hours / Liter

CNG (3600 psi): 2,500.0 W hours / Liter

NG: 10 W hours / Liter

Source: https://en.wikipedia.org/wiki/Energy_density