  We examine the distribution of injected energy in three-dimensional,
adaptive-grid simulations of the heating of cooling flows. We show that less
than 10 percent of the injected energy goes into bubbles. Consequently, the
energy input from the nucleus is underestimated by a factor of order 6 when it
is taken to be given by PVgamma/(gamma-1), where P and V are the pressure and
volume of the bubble, and gamma the ratio of principal specific heats.
