Based on a recently developed algorithm for the exploration of ground states in bond-diluted lattice spin glasses, we determine the scaling of defect energies with system size for Ising spin glasses at the bond percolation threshold p c . The results can be related by well-known scaling relations to the shape of the transition temperature T g ∼ ( p - p c ) φ between the paramagnetic and glassy regime for p → p c . The numerical results in three dimensions are consistent with rather old experimental data for ( Fe x Ni 1 - x ) 75 P 16 B 6 A 3 , suggesting that new experimental work may be able to put those numerical predictions to the test.