  Neutron stars in low-mass X-ray binaries are thought to be heated up by
accretion-induced exothermic nuclear reactions in the crust. The energy release
and the location of the heating sources are important ingredients of the
thermal evolution models. Here we present thermodynamically consistent
calculations of the energy release in three zones of the stellar crust: at the
outer-inner crust interface, in the upper layers of the inner crust (up to the
density $\rho \leq 2\times 10^{12}$ g cm$^{-3}$), and in the underlying crustal
layers. We consider three representative models of thermonuclear ashes
(Superburst, Extreme rp, and Kepler ashes). The energy release in each zone is
parametrized by the pressure at the outer-inner crust interface, which encodes
all uncertainties related to the physics of the deepest inner-crust layers. Our
calculations allow us, in particular, to set new lower limits on the net energy
release (per accreted baryon): $Q\gtrsim0.28$ MeV for Extreme rp ashes and
Q~0.43-0.51 MeV for Superburst and Kepler ashes.
