How much land for solar power for Australia?

As a good rule of thumb, we need 100 sq ft for 1 kW of panels.  That's 9.3 sq metres.  So for 1 MW (of capacity) we'd need 100,000 sq ft, or roughly 2.5 acres, or 9,300 sq m.  1 sq metre = one millionth of a square kilometre. [Update 7/9/21:  this link here says that in Australia we need 3.4 square metres for 1 kW of panels.  So we'd need even less land than I estimate in the calcs below]

Total peak demand is 33,941 MW.  Assuming a solar capacity factor of 30%, that means we'd need capacity of 113,137 MW, or 1052 sq km.  So a 32 by 32 km area, somewhere in western NSW, could supply all of Australia's electricity, ignoring rooftop solar, wind and hydro.  NSW's total area is roughy 800,000 sq kms.

A 1 GW (1000 MW) solar farm would require 9.3 sq km, or a piece of land 3 kms by 3 kms.  We'd need 113 solar farms.

Of course, we wouldn't just build out solar.  We'd have wind too, because it's complementary with solar, and we'd have rooftop solar, increasingly with storage, and hydro (+-8% of Oz's supply).

We've got plenty of space to put in all the solar farms we'll ever need.

Sunraysia NSW solar farm