The average Melbourne house produces almost 12tonnes of CO2 per year from its energy use.
Between 1/3 to 1/2 of a houses energy use goes on heating and cooling. This can mostly be removed by good passive solar design. That still leaves a large amount of impact to address if you are trying to create a Positive House. Luckily its pretty easy to choose energy efficient appliances thanks to the Energy Rating Labelling scheme. The scheme covers the major appliances in the house: the fridge, tv/computer monitor, washing machine, dishwasher, airconditioner, and dryer. The rule of thumb is that the more stars, the less energy the appliance will use, and the cheaper it will be to run. This can lead to hundreds or even thousands of dollars of savings over the usual 10 year life of the appliance. With careful selection on all appliances you can quite easily also save a couple of tonnes of CO2 per year, without any change to useage patterns! Appliance choice is very important, and should not be forgotten.
We would also suggest, that before you go shopping, go to http://reg.energyrating.gov.au/comparator/product_types/ There they have a database of products, and you can search by energy effiency. For many of the appliances you can also put in how often you are likely to use the item and work out the yearly running cost, and cost savings of choosing more efficient models.