My Wife and I live in a 4 Room Detached house in Perth.
We pay about $150 ~ $180 for 2 months for the electric bill, which included use of the aircon in the evenings during summer. During winter, its about $200 -220 due to the use of the dryer, and electric heater.
You don't have to pay for the water unless you go over the limit. we pay an average of $150 for 6 months as we go a little overboard with the watering of the garden.
For Gas, you'll be looking at around 75~80 a month.