diff --git a/packages/domain/src/domain/sap/tables/table_12_cert_calibration.py b/packages/domain/src/domain/sap/tables/table_12_cert_calibration.py
index 576307ae..48c8564c 100644
--- a/packages/domain/src/domain/sap/tables/table_12_cert_calibration.py
+++ b/packages/domain/src/domain/sap/tables/table_12_cert_calibration.py
@@ -100,13 +100,19 @@ def _build_cert_calibration_table():
     `PriceTable` value at validation-script init time."""
     from domain.sap.rdsap.cert_to_inputs import PriceTable
 
-    # Cert-calibration empirically extends the E7 off-peak set to
-    # direct-electric codes (191-196) — the cert assessor applies the
-    # off-peak rate to these even though SAP 10.2 Table 12a says 90%
-    # high-rate. Confirmed by hand-tracing cert 0800-1364 (Detached
-    # bungalow, code 191, actual SAP 71, predicted 37 before this fix).
+    # Cert-calibration empirically extends the E7 off-peak set:
+    #   191-196  direct-electric (boilers etc) — S-B11 finding
+    #   401-409  electric storage heaters (spec-correct)
+    #   421-425  high-heat-retention storage (spec-correct)
+    #   691-696  electric room heaters — S-B14 finding (cert 0340-2394:
+    #            73m² mid-floor flat, code 691, actual SAP 75, predicted
+    #            56 before this; cert software applies off-peak to all-
+    #            electric dwellings regardless of heating typology).
     cert_calibration_e7_codes = frozenset(
-        list(range(191, 197)) + list(range(401, 410)) + list(range(421, 426))
+        list(range(191, 197))
+        + list(range(401, 410))
+        + list(range(421, 426))
+        + list(range(691, 697))
     )
     return PriceTable(
         unit_price_p_per_kwh=unit_price_p_per_kwh,