Keep in mind that deserts are cold at night and hot in the daytime, and that Australia does have changing seasons.   Bearded Dragons will naturally brumate when the weather gets cooler, this usually begins the dragons second winter. 

Brumation is similar to hibernation in that it is a shutdown period for them.  However, Bearded Dragons will still be somewhat active, and will eat.  They should be provided with foods on the same daily schedule.  However, you will notice a decrease in the amount of food ingested.  Some dragons may go a few days without eating, however food should be available to them should they want it.

Brumation Resources:

Brumation information.pdf

• During the winter months (generally October or November through February) you should keep the day time temperatures the same (85*F ambient, and 105-10*F basking)

• You might find that in the winter months you need to swap out your main heat bulbs with a higher wattage bulb in order to keep your enclosure temperatures correct because the room temperature is lower.

• If it is your dragons' second winter and beyond, then daylight hours during winter months should be reduced to 8-10 hours on per day (from summer settings of 12-14 hours on per day).  This is especially important if you're planning on breeding.

  Don't forget to switch back in the spring! 
  

• If your house temperature drops below 50*F, you may want to provide a small amount of heat at night using low wattage ceramic heat emitters during very cold spells or if the enclosure is kept in a particularly cold area of the house. 

NOTE:  Under tank heaters/pads and hot rocks should not be used, because they have been known to cause burns and internal organ "cooking."  Reptiles do not thermo-regulate through their bellies, because their heat normally comes from the sun (above).

Reptiles do absorb heat from rocks, pavement, and dark surfaces, but that surface cools as the reptile basks, therefore intestinal cooking and burns are avoided, however with electronic heat sources, they don't cool down, they just keep heating, well if the lizard can't tell the temp then the lizard just hangs out there, and then they get burned or end up with intestinal issues.

Instead of a heat pad or heat rock, Kricket's Kritters recommends that you use a dome and a basking bulb for your heat.  Depending on the size of the enclosure will depend on the wattage of basking bulb.  You'll need to use whatever allows you to get the basking and ambient temperatures correct for your kritter.