We give necessary and sufficient conditions for the existence of a positive solution with zero boundary values to the elliptic equation Lu = σu q + µ in Ω, in the sublinear case 0 < q < 1, with finite generalized energy:where γ = 1 corresponds to finite energy solutions.Here Lu := − div(A∇u) is a linear uniformly elliptic operator with bounded measurable coefficients, and σ, µ are nonnegative functions (or Radon measures), on an arbitrary domain Ω ⊆ R n which possesses a positive Green function associated with L.When 0 < γ ≤ 1, this result yields sufficient conditions for the existence of a positive solution to the above problem which belongs to the Dirichlet spaceẆ 1,p 0 (Ω) for 1 < p ≤ 2.2010 Mathematics Subject Classification. Primary 35J61, 42B37; Secondary 31B10, 31B15.