Effective mass theory and variation method are used to calculate the ground state energies of excitons in coupled three-quantum dot (3-QD) systems. To calculate multicenter integrals involving two particle wave functions, a series of spheres are used to cover the coordinate space and further approximation has been made when the radii of the integral spheres are suitably selected around the three spherical QDs in near equal radius. The results obtained from the calculation of In0.5Ga0.5As/GaAs and GaAs/Al0.2Ga0.8As coupled 3-QD systems are basically in agreement with the experiments. Based on the energy level schemes in these systems, we make suggestions for the application of far-infrared and/or terahertz sources.