If we take, for example, the Ripack 3000 heat shrink gun, its consumption per hour sits between 2.9 and 4.9 kg (continued usage). With an average of 3.5 kg/h (average pressure), it is possible to shrink wrap around 120 pallets.
This is merely an indicative figure; a thick cover, the operating pressure and the dimensions of the pallet are other factors that will vary the performance.