What size tank do I need for solar hot water (average family home)?

What size tank do I need for solar hot water (average family home)?

-       As a rule of thumb, a relatively water efficient household is looking at a system size of 75 litres per person. A typical solar hot water panel is 2 square metres and will supply 150 litres. So a typical 4 person family will need a system sized at 300 litres which has 2 panels.

https://www.solarquotes.com.au/hot-water/size/