diff --git a/python/asteria/simulation.py b/python/asteria/simulation.py
index 9084673..6b1f6e2 100644
--- a/python/asteria/simulation.py
+++ b/python/asteria/simulation.py
@@ -312,11 +312,14 @@ def compute_energy_per_vol(self, *, part_size=1000):
             idx = 0
 
             # Perform integration over spectrum
-            if part_size < self.time.size:
+            if part_size <= self.time.size:
                 for idx in np.arange(0, self.time.size, part_size):
                     spectrum = self.get_combined_spectrum(self.time[idx:idx + part_size], self.energy, flavor,
                                                           self._mixing)
                     result[idx:idx + part_size] = np.trapz(spectrum, self.energy.value, axis=1)
+            else:
+                spectrum = self.get_combined_spectrum(self.time, self.energy, flavor, self._mixing)
+                result = np.trapz(spectrum, self.energy.value, axis=1)
 
             result *= (
                 H2O_in_ice *  # Target Molecule (H2O) density