Aside from the HVAC system, the lighting will likely be the largest user of electricity in a building . It is one of the most noticeable and essential systemstw 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 numbers 12, 8 & 5 represent the diameter of the lamp to the 8th of an inch. Along with the changes in diameter, there is a change in the technology driving the lamps. The ballasts have also changed 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, such as 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.