diff --git a/domain/modelling/generators/heating_recommendation.py b/domain/modelling/generators/heating_recommendation.py
index dab016843..f4f7375dc 100644
--- a/domain/modelling/generators/heating_recommendation.py
+++ b/domain/modelling/generators/heating_recommendation.py
@@ -159,7 +159,10 @@ def select_ashp_pcdb_id(design_heat_loss_kw: float) -> int:
     `design_heat_loss_kw`: the smallest ladder rung whose rated output meets the
     load (PSR >= 1.0), capped at the largest rung when the load exceeds the
     domestic aroTHERM plus range (ADR-0049)."""
-    raise NotImplementedError
+    for max_output_kw, pcdb_id in _ASHP_SIZING_LADDER:
+        if max_output_kw >= design_heat_loss_kw:
+            return pcdb_id
+    return _ASHP_SIZING_LADDER[-1][1]
 
 
 # --- Gas boiler upgrade (Heating/HW expansion): replace an existing wet boiler