There are three types of lights. Incandescent are the most popular and found in many homes. They are glass spheres filled with a gas such as argon or nitrogen. When heated by an electric current, a tungsten filament glows, causing the bulb to incandesce and the tungsten to produce visible white light. Since 90% of the energy produced by incandescent bulbs is wasted as heat, they aren’t very efficient, emitting around 15 lumens per watt. They also emit about one quarter the light as the same wattage fluorescent bulb. Halogen bulbs are about 30% more efficient than incandescent bulbs.
|This is a compact fluorescent light (CFL) bulb on the left and a common incandescent bulb on the right. It takes roughly 9 of the incandescent bulbs to emit the same light and last the same amount of time as the one fluorescent bulb on the left.
Halogen uses a tungsten filament as well but in a smaller quartz bulb (glass would melt). The gas is of the halogen family and combines with the tungsten atoms as they evaporate. This thermal radiation produces the light. Halogen bulbs run very hot and inefficiently and tend to give uneven light. Fluorescent bulbs produce light without heat. Electrodes at both ends of the fluorescent tube flow a mercury gas which gives off ultraviolet light when ionized. The ultraviolet light collides with the phosphor coating inside the tube, creating visible light. Since they don’t use heat to produce light, they are energy efficient and provide great illumination to light up the workspace. They can also produce 50-100 lumens per watt.
|Think you need a lot of light? Griot’s Garage sells this four tube fluorescent light.that emit a color temperature of 5000 degrees Kelvin, which is about as close to natural light as possible. These will set you back about $250, which is why they’re not in my garage right now!
Fluorescent bulbs are sold as T bulbs with T8 and T12 bulbs being the most popular. T8 bulbs use 20% less energy to deliver the same lumen output but can emit 27% more light per watt than a T12. They can last up to twice as long, are 90% quieter, and emit better color than T12’s. T8 bulbs have a slower lumen depreciation as well. After 10,000 hours, T8 lamps are still emitting 95% light output versus only 85% for T12 bulbs. Although the initial investment is slightly higher, the energy efficient T8 bulbs save money each month on the electricity bill.