It is said a Dragon can evaporate a whole lake.
To be a lake it needs to be at least 2 acres. That's 8,093.71 Meters Squared. Even if I lowball it to 2 Meter deep average that makes it 16,187.42 meters cubed.
That's 17,187,420 kilograms of water.
It takes 22,570 Joules to Evaporate 1 Kilogram of water.
All together that's 387,920,069,400 Joules or ~92.7 Tons of TNT. High-End City-Block Level.