diff --git a/domain/epc_prediction/historic_conditioning.py b/domain/epc_prediction/historic_conditioning.py
index a0c884e0b..82fb082b4 100644
--- a/domain/epc_prediction/historic_conditioning.py
+++ b/domain/epc_prediction/historic_conditioning.py
@@ -84,6 +84,19 @@ _FUEL_CODES: dict[str, int] = {
 
 _NOT_COMMUNITY_SUFFIX = " (not community)"
 
+# Pre-RdSAP-17 lodgements carry a deprecation rider after the fuel name; the
+# fuel named is the same physical fuel. Dominant in the pre-2012 dump (a
+# 65-shard scan: 636/663 otherwise-unresolved values were these variants).
+_LEGACY_SUFFIX = " - this is for backwards compatibility only and should not be used"
+
+# SAP-style lodgements prefix the category; map the known forms to the base
+# description the code table keys on.
+_LEGACY_ALIASES: dict[str, str] = {
+    "Gas: mains gas": "mains gas",
+    "Electricity: electricity, unspecified tariff": "electricity",
+    "dual fuel - mineral + wood": "dual fuel (mineral and wood)",
+}
+
 
 @dataclass(frozen=True)
 class HistoricConditioning:
@@ -105,6 +118,8 @@ def _wall_construction(description: str) -> Optional[int]:
 
 def _main_fuel(description: str) -> Optional[int]:
     base = description.strip().removesuffix(_NOT_COMMUNITY_SUFFIX)
+    base = base.removesuffix(_LEGACY_SUFFIX)
+    base = _LEGACY_ALIASES.get(base, base)
     return _FUEL_CODES.get(base)