The Resonance energy of Benzene is

Resonance energy is the amount of energy required to convert a delocalized structure into a stable form.

The heat of hydrogenation to reduce 1 double bond is around 120 kJ/mol and in benzene, there are 3 double bonds.

The total heat of hydrogenation of the benzene expected is 120×3=360kJ/mol
But the experimental value of heat of hydrogenation of benzene is 208kJ/mol.
So the difference between the heat of hydrogenation is due to resonance energy.

So, Resonance energy = 360-208=152kJ/mol.=36Kcal/mol.