The cross section preparation for reactor calculations produces few-group data libraries whose storage needs in memory increase severely when more physical output is requested. As a matter of fact, depletion chains with many isotopes are suggested for a more accurate isotopic inventory all along the fuel cycle, and coarse meshes are not suitable to compute finer distributions of reaction rates in highly heterogeneous systems. This work investigates the use of compression techniques on the power form factors to evaluate potential storage reduction for homogenized pin-by-pin data. The form factors are analyzed in several physical conditions of normal operation for Gd-poisoned UO2 and mixed-oxide fuel assemblies whose specifications come from a benchmark problem. Two numerical transforms are studied on two different applications, providing recommendations for general use in core calculations.