In this work we discuss the limitations of the localized transmission of electromagnetic energy at microwaves. The nondiffractive features of localized pulses are evaluated in terms of the main spot size over both the propagating and the transverse axis. By defining an original theoretical framework, we show that, even in the nondispersive case, it is not always possible to efficiently confine electromagnetic pulses. Results show that the considered fractional bandwidth plays a key role in the confinement properties of such pulses, posing well-defined constraints to the practical realization of localized pulses in the microwave range.