If your house is single phase power, the amount of rooftop solar PV that you can install will depend  on your electricity network provider, as each electricity network provider has different rules.

In almost all instances, you can install more inverter capacity than what the electricity network provider says, so long as you grid export limit your solar PV system.  Note:  Not all inverters have grid export limit capability. 

Below is a table showing the allowed capacity (inverter capacity and your grid export limit), for each of the electricity network providers for single phase households:

SA Power Networks (SA) max 10kW inverter capacity, 5kW export limit
Powercor (VIC) no inverter limit, 5kW export limit
CitiPower (VIC) no inverter limit, 5kW export limit
Ausnet Services (VIC) max 10kW inverter capacity, 5kW export limit
United Energy (VIC) max 10kW inverter capacity, 10kW export limit
Jemena (VIC)  max 10kW inverter capacity, 10kW export limit
Energex (QLD) max 10kW inverter capacity, 5kW export limit
Ausgrid (NSW) max 10kW inverter capacity, 10kW export limit
EVO Energy (ACT) max 10kW inverter capacity, 5kW export limit