Designing challenges for off-grid solar in Queensland include relatively short daylight hours. This means the battery bank should be bigger than in Victoria, where longer days are more advantageous. Major consumption comes from air cooling. Long hot nights can be very challenging for off-grid systems and affect costs, as the battery is the most expensive part of the system. However, charging batteries is not really a problem, as solar panels are very productive under the Queensland sun. The production of solar panels is very stable, even in June and July, the lowest point of the year, when 1 kW of solar produces an average of 4.5 kWh per day, and for the rest of the year, 5 to 6 kWh per kW of panel. Summer is the highest energy consumption time in Queensland, and this likely fits well with the panels’ generation capability at maximum.
For a family of three to live comfortably off-grid in Queensland, they should install a battery bank with a 24-hour capacity, which should be around 20 kWh. A 10 kW solar panel system would be plenty, and the inverter should definitely be around 10 kW to handle any cooking appliances. Check our off-grid calculator here. And systems prices here