On a new home, my advice is to fit at least 6.6kW of solar with a 5kW inverter. This is the maximum you are allowed to install on a single phase home in most parts of Australia, and is usually the best value per kW due to the way the rebate works.
If you want more than this (up tp 20kW) then you need to ask your builder to install a 3 phase power supply.
A solar system can generate about 150W per m² of roof. So for 6.6kW you want about 50m² of roof space. Ideally North facing, but East and West can work too, or a combination.
When you are taking to your architect or home builder these are the things to discuss to ensure your solar system works at max capacity:
Is there room next to the switchboard for the solar inverter? Will this be shaded from full sun? An alternative is to place the inverter in the garage.
Where will be a good place to add a future battery? Ideally this should be close to the switchboard and inverter.
Where will the drain vent pipe exit the roof? Will this shade the solar? Can it go on the south facing roof - out of the way. Can you should specify an 'Air Admittance Valve' instead of a roof penetration?
Where will your TV aerial go? Can it also go on the south roof out of the way of any solar?
If using rooftop wireless internet, where will your internet transceiver go? South facing roof again please!
If the sparky is laying new cables to the street, can he make them thicker than normal to avoid voltage drop issues? Tell the sparky you want a voltage drop less than 20V when pushing 6.6kW into the grid.
I strongly advise pre-installing the wiring for your solar system during the build. The installers can really easily and neatly pre-wire the house for solar before the walls are gyp-rocked. If the installers save time and money then the savings can be passed to you.
Get a solar-ready electricity meter installed from the outset. Then you won't have to replace it. This will save you hundreds of dollars. Ensure the builder's sparky knows to do this. By default you'll get a non-solar meter!
If you’re building a multi-storey house put your solar panels on the roof before the scaffolding comes down. You don't want to pay for scaffolding twice.
Get A Firm Quote (or quotes) 3-4 months before handover - this timing is usually ties in nicely wih get the walls pre-wired before the gyprocking happens.