Lighting, can be one of the largest usage of electricity in a building besides the HVAC systems. It is one of the most noticeable system as everyone must have light to see the task at hand. Lighting technology has come a long way from the first incandescent lamp. Fluorescent lamps have progressed from T12 to T8 to T5. The ‘T’ stands for Tube while the 12, 8 & 5 is the diameter of the lamp in 8th of an inch. Along with the changes is diameter the technology driving the lamps, the ballasts, have also changed therefore making the T8 more energy efficient that T12 and the T5 more energy efficient than the T8. There are many different lamps for many different uses, like High Intensity Discharge (HID) lamps for exterior and warehouse lighting. The HID lamps have also gone through many variations to many to discuss her, but needless to say each iteration has become more energy efficient with the lamp being the preferred current lamp to use.