So I looked into this more.
Solar storms arent just solar flares but include Coronal Mass Ejections. But the once in a 1000 year super storm bit means we can use high ends
Coronal Mass Ejections - up to
10^32 ergs | 1e+25 Joules | 1.39 Petatons of TNT (Continent level)
Solar flare - up to
1e25 Joules (page 2)
In short, generally continental (Was Kal not joking when he said hes as strong as the sun), considering their battle does affect far away locations globally (global storms have a common feat at Low 6-B too), this is consistent, and supes kinda scales cause King Shazam only goes all out after wards.
Arguably this energy output needs to be divided by 4 since Hawkman said all that was
happening from the 3 of them fighting like crazy rather than it all being King Shazam.
It does make Tornado Mode + Nth Metal Mace Kal being 5-B a little less crazy of a Jump although its still a big jump
I may make a calc for Steel's hammer being powered by a neutron star. Its made of Promethium, but if the star is literally only the diameter of the head of the hammer it'd still be pretty heavy