[en] The electronic excitations of 2H-TaSe_2 and related single crystalline systems have been investigated using electron energy-loss spectroscopy. These systems consist of hexagonal layers with weak interlayer van-der-Waals bonding. We show the influence of alkali metal intercalation on the energy position and the dispersion of the charge-carrier plasmon. Further we demonstrate how the slope of dispersion is affected by the additional charge and the change of charge-carrier density in consequence. Our results indicate a universal evolution of the plasmon dispersion independent of the intercalant (Na, K) and the dichalcogenide (TaSe_2, TaS_2, NbSe_2).