Regarding fuel consumption, we always talk about the pricing of natural gas on a gasoline litre or diesel litre equivalent. Natural gas and gasoline have very comparable efficiencies in terms of how much fuel is burned in the engine. So if it's 12 litres per 100 kilometres, it would be 12 gasoline litre equivalents per 100 kilometres. There is pretty much parity on the efficiency side, but you need more volume on the vehicle to hold the same amount of energy. That's the difference.
On May 17th, 2012. See this statement in context.