Aloe Terra - Lawrence Tech University 2007 Solar Decathlon Team

Incandescent light bulbs are the least efficient of the four mentioned. The light created by these bulbs is merely a byproduct of heating up a metal filament. Only about 5% of the energy consumed by incandescent bulbs is actually used to produce light! Because of their inefficiency, incandescent light bulbs are slowly being replaced by fluorescent bulbs and LEDs. Incandescent light bulbs remain popular, however, because of their low initial cost and their voltage variety.

Halogen light bulbs are slightly more efficient than incandescent light bulbs. Like incandescent bulbs, halogen bulbs produce light by heating up a metal filament. Unlike incandescent bulbs, halogen bulbs contain a halogen gas that maintains equilibrium inside the bulb. This equilibrium increases the longevity and the light intensity of the bulb. In addition to lasting longer than incandescent light bulbs, halogen bulbs are favored because they are designed to fit most fixtures.

Fluorescent light bulbs do not use heat to produce light, making them inherently more energy-efficient than incandescent bulbs and halogen bulbs. Instead of using heat, fluorescent light bulbs channel electricity through a gas-filled tube. When the electricity and gas collide, an ultraviolet radiation is produced. This radiation causes a phosphor coating on the inside of the tube to generate light.

A fluorescent light bulb is more expensive than an incandescent bulb and a halogen bulb but will generally last 10 times longer and is significantly less expensive to use. Because of their efficiency, fluorescent light bulbs are actually less expensive per watt than incandescent bulbs and halogen bulbs.

The most efficient light currently on the market is a light-emitting diode (LED). LEDs have been available for years, but were traditionally used for their ability to produce bright red, green, and yellow. In recent years, technology has enabled LEDs to create a bright white light that is practical for residential lighting. Unlike incandescent light bulbs, LEDs do not contain a filament that can burn out or create light from heat. LEDs are illuminated by electrons moving in a semiconductor material. The efficiency of LEDs is higher than that of any other light on the market today. They can last for years and be used in a number of different applications. Like fluorescent light bulbs, LEDs save on energy cost due to their efficiency and longevity.

• Replace incandescent and halogen light bulbs with fluorescent lights or LEDs.
• Turn lights off when they're unnecessary.
• Consider occupancy sensors that automatically turn lights on and off.
• Install dimmers to light switches.
• Let the sunshine illuminate your home.