  We estimate the fraction of the total energy in a Gamma-Ray Burst (GRB) that
is radiated in photons during the main burst. Random internal collisions among
different shells limit the efficiency for converting bulk kinetic energy to
photons. About 1% of the energy of explosion is converted to radiation, in
10-1000 kev energy band in the observer frame, for long duration bursts
(lasting 10s or more); the efficiency is significantly smaller for shorter
duration bursts. Moreover, about 50% of the energy of the initial explosion
could be lost to neutrinos during the early phase of the burst if the initial
fireball temperature is about 10 Mev or greater. If isotropic, the total energy
budget of the brightest GRBs is about $10^{55}$erg, a factor of more than 20
larger than previously estimated. Anisotropy of explosion, as evidenced in two
GRBs, could reduce the energy requirement by a factor of 10-100. Putting these
two effects together we find that the energy release in the most energetic
bursts is about 10$^{54}$ erg.
