The function of the fixture is to efficiently direct light without causing glare or discomfort. T-5 fluorescent lamps are also becoming more common. For more in-depth information, refer to the SmarterEnergy technical article on Compact Fluorescents . Poorly suited for most commercial and industrial applications and very inefficient. There are also new HIDs which are smaller and suitable for retail display lighting.
Mercury vapor is an older technology and is the least efficient.
A new technology for use in very large scale commercial or industrial applications like malls and convention centers. They offer efficacies approaching 100 lumens per watt, the highest of any commercial energy source. For more in-depth information, refer to the SmarterEnergy technical article on Sulfur Lamps . The efficacies of common lamps are shown in the Figure 1. All fluorescent lights use a power conditioning device called a ballast that amplifies line voltage to start the lamp, and limits current to maintain its arc.