Unity energy bar example

energy-bar.cs

using UnityEngine;
using System.Collections;

public class PlayerHealth : MonoBehaviour {
	Vector2 pos = new Vector2(10, 10);
	Vector2 size = new Vector2(200, 16);

	float barFill = 0.8f;
	string barText = "Health";

	public GUIStyle progress_empty;
	public GUIStyle progress_full;
		
	void OnGUI () {
		// Create a group container to make positioning easier
		GUI.BeginGroup(new Rect(pos.x, pos.y, size.x, size.y));
		
		// Draw the background and fill
		GUI.Box(new Rect(0, 0, size.x, size.y), barText, progress_empty);
		GUI.Box(new Rect(0, 0, size.x * barFill, size.y), barText, progress_full);
		
		GUI.EndGroup();
	}

	void Update () {
		// Poll the player's health from stats object here
		// barFill = 8 / 10;
	}
}