diff --git a/OpenRa.Game/Graphics/WorldRenderer.cs b/OpenRa.Game/Graphics/WorldRenderer.cs
index ec9ba83177..41bcfebd4e 100644
--- a/OpenRa.Game/Graphics/WorldRenderer.cs
+++ b/OpenRa.Game/Graphics/WorldRenderer.cs
@@ -107,7 +107,7 @@ namespace OpenRa.Game.Graphics
 				Game.OreTime * 1000,
 				Game.LocalPlayer.Cash,
 				PerfHistory.items[ "nodes_expanded" ].LastValue,
-				Game.LocalPlayer.Power
+				Game.LocalPlayer.GetTotalPower()
 				), new int2(5, 5), Color.White);
 
 			PerfHistory.Render(renderer, lineRenderer);
diff --git a/OpenRa.Game/Player.cs b/OpenRa.Game/Player.cs
index c3b08fdc17..76d43c7e59 100644
--- a/OpenRa.Game/Player.cs
+++ b/OpenRa.Game/Player.cs
@@ -11,7 +11,8 @@ namespace OpenRa.Game
 		public Race Race;
 		public readonly int Index;
 		public int Cash;
-		public int Power;
+		int powerProvided;
+		int powerDrained;
 
 		public Player( int index, int palette, string playerName, Race race )
 		{
@@ -20,7 +21,20 @@ namespace OpenRa.Game
 			this.PlayerName = playerName;
 			this.Race = race;
 			this.Cash = 10000;
-			this.Power = 0;
+			this.powerProvided = this.powerDrained = 0;
+		}
+
+		public void ChangePower(int dPower)
+		{
+			if (dPower > 0)
+				powerProvided += dPower;
+			if (dPower < 0)
+				powerDrained -= dPower;
+		}
+
+		public int GetTotalPower()
+		{
+			return powerProvided - powerDrained;
 		}
 
 		public float GetSiloFullness()
diff --git a/OpenRa.Game/Traits/Building.cs b/OpenRa.Game/Traits/Building.cs
index 4f1890680a..0894e00baf 100644
--- a/OpenRa.Game/Traits/Building.cs
+++ b/OpenRa.Game/Traits/Building.cs
@@ -26,7 +26,7 @@ namespace OpenRa.Game.Traits
 			UnitInfo.BuildingInfo bi = self.unitInfo as UnitInfo.BuildingInfo;
 			if (bi == null) return;
 
-			self.Owner.Power += bi.Power;
+			self.Owner.ChangePower(bi.Power);
 		}
 	}
 }