diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index af8af3bce..4b4558718 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -114,6 +114,19 @@ def test_electric_boiler_decodes_to_191_and_drags_electricity() -> None:
     assert simulation.heating.main_fuel_type == 29
 
 
+def test_electric_cpsu_decodes_to_192_electric_on_an_off_peak_meter() -> None:
+    # An electric "Boiler: A rated CPSU" was funnelled into mains-gas Gas CPSU
+    # (120). Electric CPSU is SAP Table 4a 192, electric (29), charging overnight on
+    # a Dual off-peak meter (§12 Rule 1, 10-hour) — ADR-0045.
+    simulation = main_heating_overlay_for("Electric CPSU", 0)
+
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.sap_main_heating_code == 192
+    assert simulation.heating.main_fuel_type == 29
+    assert simulation.heating.meter_type == "Dual"
+
+
 @pytest.mark.parametrize(
     ("main_heating_value", "code"),
     [