diff --git a/nowcasting_datamodel/read/read_gsp.py b/nowcasting_datamodel/read/read_gsp.py
index 44d06518..d5b05a0c 100644
--- a/nowcasting_datamodel/read/read_gsp.py
+++ b/nowcasting_datamodel/read/read_gsp.py
@@ -1,4 +1,5 @@
 """ Read pv functions """
+import logging
 from typing import List, Union
 
 from sqlalchemy import desc
@@ -6,6 +7,8 @@
 
 from nowcasting_datamodel.models import GSPYieldSQL, LocationSQL
 
+logger = logging.getLogger(__name__)
+
 
 def get_latest_gsp_yield(
     session: Session, gsps: List[LocationSQL], append_to_gsps: bool = False, regime: str = "in-day"
@@ -47,6 +50,8 @@ def get_latest_gsp_yield(
     # get all results
     gsp_yields: List[GSPYieldSQL] = query.all()
 
+    logger.debug(f"Found {len(gsp_yields)}  latest gsp yields")
+
     if not append_to_gsps:
         return gsp_yields
     else:
@@ -58,16 +63,20 @@ def get_latest_gsp_yield(
 
             gsp_systems_with_gsp_yields.append(gsp)
 
+        logger.debug(f"Found {len(gsp_systems_with_gsp_yields)} gsps with yields")
+
         # add pv systems that dont have any pv yields
         gsp_systems_with_gsp_yields_ids = [gsp.id for gsp in gsp_systems_with_gsp_yields]
 
         gsp_systems_with_no_gsp_yields = []
         for gsp in gsps:
-            if gsp.gsp_id not in gsp_systems_with_gsp_yields_ids:
+            if gsp.id not in gsp_systems_with_gsp_yields_ids:
                 gsp.last_gsp_yield = None
 
                 gsp_systems_with_no_gsp_yields.append(gsp)
 
+        logger.debug(f"Found {len(gsp_systems_with_gsp_yields)} gsps with no yields")
+
         all_gsp_systems = gsp_systems_with_gsp_yields + gsp_systems_with_no_gsp_yields
 
         return all_gsp_systems