Osmosis, simply put, is just the diffusion of water molecules. Just like diffusion, it requires no energy from ATP, it is not a metabolic process like active transport (transfer of molecules AGAINST a potential gradient). However, dead potato cells still have cell walls and cell membranes, hence, osmosis, transfer of water molecules still occurs between cells. For instance- from 0kPa to -4000kPa. within plant cells.
It is just a process like diffusion, to attain an equilibrium, so no energy is required, all follows the flow of a higher water potential to one of lower water potential (across a potential gradient)