Variability in energy deposition caused by intrinsic statistical fluctuations is quantified for specific radiation environments. Differences in effective flux are observed for minimally ionizing particles, typically leading to a decrease in predicted soft error rate, the magnitude of which depends on the threshold LET. When compared to spectra accounting for energy-deposition fluctuations, predictions with traditional LET spectra in CREME96 are found to lead to conservative estimates in almost all situations.