Types of Light Bulbs
Modern residential lighting falls into four types:
1. Incandescent bulbs are the most commonly used light bulbs. Incandescent bulbs give off a warm-colored light. They are the least expensive to buy, but are inefficient because they lose much of their energy as heat instead of light.
2. Halogen bulbs are a type of incandescent, but they are more efficient and last longer than traditional incandescent bulbs. They are particularly useful for spot or task lighting since they give off an intense, focused light.
3. Fluorescent tubes have been commonplace in institutional settings for many years. Newer compact fluorescent tubes and bulbs are smaller, quieter, and emit a better color of light, and are gaining acceptance in residential applications. There are still issues with installing them outdoors in cold environments and with using them with dimmers. Fluorescent lighting is the most energy-efficient lighting, but the bulbs are more expensive to buy. However, they last 3 to 4 times longer than standard bulbs.
4. LEDs (light emitting diodes) are small solid bulbs which are extremely efficient, durable and long-lasting. Because they don't have a filament, they are not easily damaged. They can stand up to incredible abuse. They also last 10 times longer than compact fluorescents and well over a hundred times longer than typical incandescent bulbs. At present, their common application seems to be limited to single bulb use in such things as electronics, instrument panels and more recently Christmas tree lights. Many cities are replacing incandescent traffic lights with LED arrays because they can reduce electrical consumption by as much as 80 percent. At this point they are not commonly used to replace every day lighting. The cost is still prohibitive, but will become more affordable over time.
Saving Energy
The efficiency of lights is typically expressed as lumens per watt (lpw) which is the amount of light given off per unit of energy. Halogen bulbs top out at 22 lpw, whereas fluorescent can go as high as 80 lpw. So if 10 percent of your energy bill is lighting (a typical number according to the US Department of Energy) and you can reduce that by 60 percent by changing to compact fluorescent lights, you could save $60 on a $1000/year bill.
You can also save energy by using only as much light as you need and by turning lights off when you leave the room (leave fluorescent lights on if you will return within 15 minutes). Putting lights on timers or motion sensors can also save energy while providing safety.
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