Definition
Solar Unit = the solar power striking the earth as a whole averaged throughout the day and throughout the year. (200W/m2)
Energy Consumption in solar units
1 “boiling water” 10-1 “tropical climate” 10-2 absolute upper limit 10-3 U.S. level
Source
A global view of solar energy in rational units. originated by A. Rose Phys. stat. sol (a) 56, 11 1979.