My approach to Universal Cables rendering power. They render with

transparency proportional to the base 10 log of power, to compensate
for the wide range of power that can be transmitted, and minimise client
update packets.

common/mekanism/client/EnergyClientUpdate.java

@@ -0,0 +1,41 @@
+package mekanism.client;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import mekanism.api.Object3D;
+import mekanism.common.EnergyNetwork.NetworkFinder;
+import mekanism.common.IUniversalCable;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.world.World;
+
+public class EnergyClientUpdate
+{	
+	public NetworkFinder finder;
+	
+	public World worldObj;
+	
+	public double energyScale;
+	
+	public EnergyClientUpdate(TileEntity head, double power)
+	{
+		worldObj = head.worldObj;
+		energyScale = power;
+		finder = new NetworkFinder(head.worldObj, Object3D.get(head));
+		System.out.println(power);
+	}
+	
+	public void clientUpdate()
+	{
+		List<Object3D> found = finder.exploreNetwork();
+		
+		for(Object3D object : found)
+		{
+			TileEntity tileEntity = object.getTileEntity(worldObj);
+			if(tileEntity instanceof IUniversalCable)
+			{
+				((IUniversalCable)tileEntity).setEnergyScale(energyScale);
+			}
+		}
+	}
+}

common/mekanism/common/EnergyNetwork.java

@@ -12,6 +12,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import cpw.mods.fml.common.FMLCommonHandler;
+
 import mekanism.api.IStrictEnergyAcceptor;
 import mekanism.api.ITransmitterNetwork;
 import mekanism.api.Object3D;
@@ -19,6 +21,8 @@ import mekanism.api.TransmitterNetworkRegistry;
 import net.minecraft.tileentity.TileEntity;
 import net.minecraft.world.World;
 import net.minecraftforge.common.ForgeDirection;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.Event;
 import net.minecraftforge.event.ForgeSubscribe;
 import net.minecraftforge.event.world.ChunkEvent;
 import buildcraft.api.power.IPowerReceptor;
@@ -32,9 +36,11 @@ public class EnergyNetwork implements ITransmitterNetwork
 	public Set<TileEntity> possibleAcceptors = new HashSet<TileEntity>();
 	public Map<TileEntity, ForgeDirection> acceptorDirections = new HashMap<TileEntity, ForgeDirection>();
 	
+	private double lastPowerScale = 0;
 	private double joulesTransmitted = 0;
 	private double joulesLastTick = 0;
 	private int ticksSinceCreate = 0;
+	private int ticksSinceSecond = 0;
 	private boolean fixed = false;
 	
 	public EnergyNetwork(IUniversalCable... varCables)
@@ -210,6 +216,14 @@ public class EnergyNetwork implements ITransmitterNetwork
 				}
 			}
 		}
+		
+		double currentPowerScale = getPowerScale();
+		if(FMLCommonHandler.instance().getEffectiveSide().isServer())
+		{
+			lastPowerScale = currentPowerScale;
+
+			MinecraftForge.EVENT_BUS.post(new EnergyTransferEvent(this, currentPowerScale));
+		}
 	}
 
 	public void merge(EnergyNetwork network)
@@ -393,6 +407,19 @@ public class EnergyNetwork implements ITransmitterNetwork
 		}
 	}
 	
+	public static class EnergyTransferEvent extends Event
+	{
+		public final EnergyNetwork energyNetwork;
+		
+		public final double power;
+		
+		public EnergyTransferEvent(EnergyNetwork network, double currentPower)
+		{
+			energyNetwork = network;
+			power = currentPower;
+		}
+	}
+	
 	public static class NetworkLoader
 	{
 		@ForgeSubscribe
@@ -436,6 +463,19 @@ public class EnergyNetwork implements ITransmitterNetwork
 				fixMessedUpNetwork(cables.iterator().next());
 			}
 		}
+		
+		double currentPowerScale = getPowerScale();
+		if(currentPowerScale != lastPowerScale && FMLCommonHandler.instance().getEffectiveSide().isServer())
+		{
+			lastPowerScale = currentPowerScale;
+
+			MinecraftForge.EVENT_BUS.post(new EnergyTransferEvent(this, currentPowerScale));
+		}
+	}
+	
+	public double getPowerScale()
+	{
+		return joulesLastTick == 0 ? 0 : Math.min(Math.ceil(Math.log10(getPower())*2)/10, 1);
 	}
 	
 	public void clearJoulesTransmitted()

common/mekanism/common/IUniversalCable.java

@@ -45,4 +45,6 @@ public interface IUniversalCable
 	 */
 	public void fixNetwork();
 
+	public void setEnergyScale(double energyScale);
+
 }

common/mekanism/common/Mekanism.java

@@ -17,6 +17,7 @@ import mekanism.api.InfuseType;
 import mekanism.api.InfusionInput;
 import mekanism.api.Object3D;
 import mekanism.client.SoundHandler;
+import mekanism.common.EnergyNetwork.EnergyTransferEvent;
 import mekanism.common.FluidNetwork.FluidTransferEvent;
 import mekanism.common.IFactory.RecipeType;
 import mekanism.common.MekanismUtils.ResourceType;
@@ -1214,6 +1215,14 @@ public class Mekanism
 		logger.info("[Mekanism] Mod loaded.");
 	}
 	
+	@ForgeSubscribe
+	public void onEnergyTransferred(EnergyTransferEvent event)
+	{
+		try {
+			PacketHandler.sendPacket(Transmission.ALL_CLIENTS, new PacketTransmitterTransferUpdate().setParams(TransmitterTransferType.ENERGY, event.energyNetwork.cables.iterator().next(), event.power));
+		} catch(Exception e) {}
+	}
+	
 	@ForgeSubscribe
 	public void onGasTransferred(GasTransferEvent event)
 	{

common/mekanism/common/TileEntityUniversalCable.java

@@ -4,6 +4,10 @@ import java.util.HashSet;
 
 import mekanism.api.Object3D;
 import mekanism.api.TransmitterNetworkRegistry;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.network.INetworkManager;
+import net.minecraft.network.packet.Packet;
+import net.minecraft.network.packet.Packet132TileEntityData;
 import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.AxisAlignedBB;
 import net.minecraft.world.World;
@@ -22,6 +26,8 @@ public class TileEntityUniversalCable extends TileEntity implements IUniversalCa
 	/** The energy network currently in use by this cable segment. */
 	public EnergyNetwork energyNetwork;
 	
+	public double energyScale;
+	
 	public TileEntityUniversalCable()
 	{
 		powerHandler = new PowerHandler(this, PowerHandler.Type.STORAGE);
@@ -40,12 +46,6 @@ public class TileEntityUniversalCable extends TileEntity implements IUniversalCa
 		return getNetwork(true);
 	}
 	
-	public float getEnergyScale()
-	{
-		//TODO: Let the client know how much power's being transferred
-		return 1.F;
-	}
-	
 	@Override
 	public EnergyNetwork getNetwork(boolean createIfNull)
 	{
@@ -161,4 +161,29 @@ public class TileEntityUniversalCable extends TileEntity implements IUniversalCa
 		invalidate();
 		TransmitterNetworkRegistry.getInstance().pruneEmptyNetworks();
 	}
+	
+	@Override
+	public void setEnergyScale(double scale)
+	{
+		energyScale = scale;
+	}
+
+	@Override
+	public Packet getDescriptionPacket()
+	{
+		energyScale = getNetwork().getPowerScale();
+		NBTTagCompound nbtTag = new NBTTagCompound();
+		nbtTag.setDouble("energyScale", energyScale);
+		return new Packet132TileEntityData(this.xCoord, this.yCoord, this.zCoord, 1, nbtTag);
+	}
+
+	public void onDataPacket(INetworkManager net, Packet132TileEntityData packet)
+	{
+		setEnergyScale(packet.customParam1.getDouble("energyScale"));
+	}
+	
+	public float getEnergyScale()
+	{
+		return (float)energyScale;
+	}
 }

common/mekanism/common/network/PacketTransmitterTransferUpdate.java

@@ -3,6 +3,7 @@ package mekanism.common.network;
 import java.io.DataOutputStream;
 
 import mekanism.api.EnumGas;
+import mekanism.client.EnergyClientUpdate;
 import mekanism.client.GasClientUpdate;
 import mekanism.client.FluidClientUpdate;
 import net.minecraft.entity.player.EntityPlayer;
@@ -18,6 +19,8 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
 	
 	public TileEntity tileEntity;
 	
+	public double power;
+	
 	public String gasName;
 	
 	public FluidStack fluidStack;
@@ -36,6 +39,9 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
 		
 		switch(activeType)
 		{
+			case ENERGY:
+				power = (double)data[2];
+				break;
 			case GAS:
 				gasName = ((EnumGas)data[2]).name;
 				break;
@@ -57,6 +63,17 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
 		int z = dataStream.readInt();
 		
 		if(transmitterType == 0)
+		{
+			double powerLevel = dataStream.readDouble();
+			
+			TileEntity tileEntity = world.getBlockTileEntity(x, y, z);
+			
+			if(tileEntity != null)
+			{
+				new EnergyClientUpdate(tileEntity, powerLevel).clientUpdate();
+			}
+		}
+		else if(transmitterType == 1)
 	    {
     		EnumGas type = EnumGas.getFromName(dataStream.readUTF());
     		
@@ -67,7 +84,7 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
     			new GasClientUpdate(tileEntity, type).clientUpdate();
     		}
 	    }
-	    else if(transmitterType == 1)
+	    else if(transmitterType == 2)
 	    {
     		TileEntity tileEntity = world.getBlockTileEntity(x, y, z);
     		FluidStack fluidStack = new FluidStack(dataStream.readInt(), dataStream.readInt());
@@ -90,6 +107,9 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
 		
 		switch(activeType)
 		{
+			case ENERGY:
+				dataStream.writeDouble(power);
+				break;
 			case GAS:
 				dataStream.writeUTF(gasName);
 				break;
@@ -102,6 +122,7 @@ public class PacketTransmitterTransferUpdate implements IMekanismPacket
 	
 	public static enum TransmitterTransferType
 	{
+		ENERGY,
 		GAS,
 		FLUID
 	}