The best way to save money is not to spend it in the first place!
Have you considered external influences on design and simple things you can do to reduce the workload on your air conditioner.
Shading is one area often overlooked when air-conditioning your house particularly in the hot Perth Climate.
Shading of the building and outdoor spaces from direct sunlight can block up to 90 percent of this heat, this in turn can reduce your energy bill as your air conditioner will not have to work as hard.
Shading of glass to reduce unwanted heat gain is critical. Unprotected glass is often the greatest source of unwanted heat gain in a home. Make sure if building a new home you include eaves, have outdoor blinds or blockout curtains. This simple task will improve performance of your aircon as heat from the sun is blocked before it can enter your house.
Radiant heat from the sun passes through glass and is absorbed by building elements and furnishings, which then re-radiate it. Re-radiated heat has a different wavelength and cannot pass back out through the glass as easily. In most climates, ‘trapping’ radiant heat is desirable for winter heating but must be avoided in summer.
Shading of wall and roof surfaces is important to reduce summer heat gain, particularly if they are dark coloured and/or heavyweight.
Suggested shading below;
View http://www.yourhome.gov.au/technical/fs44.html for more suggestions