  Several systems display an equilibrium condensation transition, where a
finite fraction of a conserved quantity is spatially localized. The presence of
two conservation laws may induce the emergence of such transition in an
out-of-equilibrium setup, where boundaries are attached to different and
subcritical heat baths. We study this phenomenon in a class of stochastic
lattice models, where the local energy is a general convex function of the
local mass, mass and energy being both globally conserved in the isolated
system. We obtain exact results for the nonequilibrium steady state (spatial
profiles, mass and energy currents, Onsager coefficients) and we highlight
important differences between equilibrium and out-of-equilibrium condensation.
