diff --git a/backend/services/forecast_service.py b/backend/services/forecast_service.py
index d222b21..a950487 100644
--- a/backend/services/forecast_service.py
+++ b/backend/services/forecast_service.py
@@ -19,8 +19,11 @@ logger = logging.getLogger(__name__)
 
 
 def _db_azimuth_to_pvlib(surface_azimuth_db_deg: float) -> float:
-    """DB: 0=jih, 90=západ, -90=východ → pvlib (N=0, E=90, S=180, W=270)."""
-    return float((surface_azimuth_db_deg + 180) % 360)
+    """
+    EMS DB používá standardní azimut (kompasové stupně):
+    N=0, E=90, S=180, W=270 (stejně jako pvlib).
+    """
+    return float(surface_azimuth_db_deg % 360)
 
 
 async def fetch_pv_forecast(site_id: int, db) -> tuple[int, int]: