Abstract The energy process model with geometric distributed lag (GDL) demand, called the energy GDL process model, often distinguishes several regions. This paper presents a new decomposition approach, based on the Dantzig–Wolfe principle, to decompose such a model by region in order to provide a more manageable tool for long-run energy planning and energy-related environmental protection decision making. The new decomposition approach is required because most energy GDL process models cannot be converted into optimization problems, so that the existing linear or nonlinear decomposition principles cannot be applied to such models directly. A two-region energy GDL process model of supplies and demands of oil, gas, electricity, and coal in Canada is presented and solved with the new decomposition approach, to aid in understanding the performance of the new decomposition procedure.