A 6.6kW system is the magic number in the industry. It is the most quoted system size and is the largest sized system that can be installed on a single-phase property based on network distribution solar inverter rules. On single phase supply, any solar system installed above 6.6kW will be export limited by the DNSP, NOT the retailer.
A 6.66kW system is generally recommended for a household of 4-5 people with high energy usage (around 10-16kWh per day) costing approximately $150 per month (this is an approximation and will depend on individual circumstances). It can produce an estimated 14-16kW per day in winter and 26-30kW – even up to 40kW – per day in summer. You would need enough space on your roof to fit 16 -20 panels, depending on the panel output or watt size.