diff --git a/openelectricity/client.py b/openelectricity/client.py
index c7d53b5..8fdf50b 100644
--- a/openelectricity/client.py
+++ b/openelectricity/client.py
@@ -530,24 +530,26 @@ async def get_network_data(
     async def get_facility_data(
         self,
         network_code: NetworkCode,
-        facility_code: str | list[str],
-        metrics: list[DataMetric],
+        facility_code: str | list[str] | None = None,
+        metrics: list[DataMetric] | None = None,
         interval: DataInterval | None = None,
         date_start: datetime | None = None,
         date_end: datetime | None = None,
+        unit_code: str | list[str] | None = None,
     ) -> TimeSeriesResponse:
         """Get facility data for specified metrics."""
         logger.debug(
             "Getting facility data for %s/%s (metrics: %s, interval: %s)",
             network_code,
-            facility_code,
+            facility_code or unit_code,
             metrics,
             interval,
         )
         await self._ensure_client()
         params = {
             "facility_code": facility_code,
-            "metrics": [m.value for m in metrics],
+            "unit_code": unit_code,
+            "metrics": [m.value for m in metrics] if metrics else None,
             "interval": interval,
             "date_start": date_start.isoformat() if date_start else None,
             "date_end": date_end.isoformat() if date_end else None,