Energy ratings currently only rate the energy efficiency of the building fabric ie they rate the amount of heating or cooling required to keep your house comfortable. They do not rate the efficiency of your hot water system, heating and cooling unit, or any appliances you have. It is anticipated that the 2022 update of the Building code will incorporate the efficiency of these other services and appliances within the total home energy rating.
Speak to an energy rater to do a preliminary energy rating on your design rather than just doing it at the end of the design process for building certification. Use the preliminary rating as a design assistance tool. Test the design's performance and aim to go higher than required minimum energy rating of 6 stars.
Australian NatHERS (National Home Energy Rating Scheme) residential energy ratings go up to a possible 10 stars. So the current minimum of 6 stars is really 6 out of 10 stars. Just better than a pass!
A 10 star house means no energy is required to heat or cool a house. In terms of energy this is effectively a passive house.
Industry consensus is that 7.5 - 8 stars is readily achievable with good passive design (smart room, window, and shading placement) and good well installed glazing and insulation, without being an overly significant impact on cost.