Australia (all of it!)
Most of South America: Chile (darkest on the map!), Bolivia, Argentina, Brazil.
Mexico and Cuba (everywhere), all of Central America
Western US
Africa (everywhere) Middle East (everywhere) Mongolia, North and Western China, Tibet
* The solar potential of a gloomy, northern locale like the UK is "only" half of somewhere sunny like Australia. Though I can imagine the swings between seasons are greater.
* Northern Canada has a surprising amount of potential, compared to European regions at the same latitude