diff --git a/roseau/load_flow/models/buses.py b/roseau/load_flow/models/buses.py
index 08d3ad2b..928ff1e1 100644
--- a/roseau/load_flow/models/buses.py
+++ b/roseau/load_flow/models/buses.py
@@ -279,7 +279,8 @@ def get_connected_buses(self) -> Iterator[Id]:
                 to_add = set(element._connected_elements).difference(visited)
                 remaining.update(to_add)
 
-    def res_voltage_unbalance(self) -> float:
+    @ureg_wraps("percent", (None,), strict=False)
+    def res_voltage_unbalance(self) -> Q_[float]:
         """Calculate the voltage unbalance on this bus according to the IEC definition.
 
         Voltage Unbalance Factor:
diff --git a/roseau/load_flow/models/tests/test_buses.py b/roseau/load_flow/models/tests/test_buses.py
index b6f7586c..24fe9749 100644
--- a/roseau/load_flow/models/tests/test_buses.py
+++ b/roseau/load_flow/models/tests/test_buses.py
@@ -335,18 +335,18 @@ def test_res_voltage_unbalance():
 
     # Balanced system
     bus._res_potentials = np.array([va, vb, vc])
-    assert np.isclose(bus.res_voltage_unbalance(), 0)
+    assert np.isclose(bus.res_voltage_unbalance().m_as("percent"), 0)
 
     # Unbalanced system
     bus._res_potentials = np.array([va, vb, vb])
-    assert np.isclose(bus.res_voltage_unbalance(), 100)
+    assert np.isclose(bus.res_voltage_unbalance().m_as("percent"), 100)
 
     # With neutral
     bus = Bus("b3n", phases="abcn")
     bus._res_potentials = np.array([va, vb, vc, 0])
-    assert np.isclose(bus.res_voltage_unbalance(), 0)
+    assert np.isclose(bus.res_voltage_unbalance().m_as("percent"), 0)
     bus._res_potentials = np.array([va, vb, vb, 0])
-    assert np.isclose(bus.res_voltage_unbalance(), 100)
+    assert np.isclose(bus.res_voltage_unbalance().m_as("percent"), 100)
 
     # Non 3-phase bus
     bus = Bus("b1", phases="an")