Local, discrete models of self-interacting multisite adsorption cells have been shown to be able to provide a coarse-grained representation of equilibrium properties of small molecules adsorbed in nanoporous materials at the mesoscopic scale. In the present work we show how the essential statistical properties of a host cell of structured sites with multiple adsorption energies and particle-particle interactions (that is the partition function, the average energy, and the average number of guests close to the windows connecting the cell to its surroundings) can be reproduced by a less-structured cell with two occupancy-dependent adsorption energy levels.