"The US Navy has committed to having half of its energy needs provided by non-fossil fuel sources by 2020 for its combat ships, aircraft and land vehicles."
Another comparison I will add: the Air Force is the biggest consumer of fossil fuels in the whole U.S military.
Australian Defence will have a lot of work ahead of them if pressed to burn less fossil fuel.
Clean energy efforts are useful but it won't make up for the frightful fuel consumption of some of our current and future weapons systems planned by Australian Defence.
As an aside for force structure planning: Australia will never have credible weapons systems that can take on high end threats. So any green force structure has to be based around the idea of second tier-threat war fighting.
For fossil fuel consumption the path ahead does not look good.
To illustrate, we just retired the F-111 for no valid reason. This aircraft had distance and persistence and growth room for more modern air-to-ground weapons. This aircraft would use less or no air-to-air refueling assets to perform its mission. Traditional fighter aircraft cannot beat the F-111 for its utility.
(click image to make larger-source: http://www.ausairpower.net)
How about fighter aircraft? Australia has scores of second-tier, short range fighters that burn a lot of fuel. The F-18 family of fighter aircraft are the shortest range in their class and will require more tanker gas. Fuel is always more expensive (per liter/gallon) when air refueling.
Australia doesn't need air warfare destroyers and large amphibious ships. These ships will burn more fuel than frigates and smaller (scalable) amphibious transports.
Australia acquired used M-1 tanks from the U.S.; to use for what I am not sure. This particular class of tank with its turbine engine burns up fuel at an alarming rate.
The helicopter road map for Defence (If it is big, bloated, under-tested, risky and slow to field to the warfighter it must be good) also is hard to take seriously in the area of consuming less fossil fuel.
I am not convinced that--besides platitude and side-show--Australian Defence has a handle on its fossil fuel use. Any claims to be more fuel efficient will need significant proof.