An incandescent lamp uses about 80 percent of the electricity consumed to produce heat and only about 20 percent to provide light, whereas a fluorescent lamp is just the opposite.
Wattage rating does not indicate light intensity...
To fully understand the energy-saving opportunities with lighting systems, we need to first understand that the wattage rating of a lighting device refers only to the amount of electricity consumed by the light.
The wattage rating gives no indication of the amount or intensity of the light produced by the device. The measure of the intensity of the light output is the rating of lumens. The light level reaching the target surface--whether it is a desktop, floor, or other work area--is the foot candles, as measured by a light meter. Always look for the ratings for watts and lumens on the packaging material for light bulbs when making purchases.
When selecting the type of lights to purchase for energy efficiency, make the selection on the basis of lumens per watt.
A compact fluorescent lamp (CFL) has a much higher lumens-per-watt rating than a standard incandescent light bulb.
- A CFL looks like a thin fluorescent tube wrapped around itself with an overall shape similar to an incandescent lamp.
- The CFL can be screwed into a standard incandescent socket, although in some cases the light shade or globe might not fit because a CFL is somewhat larger than an incandescent bulb.
- A CFL uses 20 to 25 percent of the amount of energy to produce the same amount of light as an incandescent lamp and they are sold in a variety of sizes.
- The life of a CFL is about ten times longer than a typical incandescent.
- The life for a CFL used for three to four hours per day is about seven years.
- A big disadvantage of the CFL is that the price is in the range of $3 to $4 per bulb, although the extra cost can be justified economically if the lamp is used at least three hours a day. Whenever purchasing a CFL, be sure to watch for store promotions and rebate coupons that will reduce the effective cost of these new lamps.
- Another disadvantage is a 15- to 30-second "warm-up time" for the CFL to get up to its full light intensity.
- Caution: Do not use CFL in a light fixture controlled by a dimmer switch, a fixture with totally enclosed globes, or a fixture exposed to the elements of weather.
The use of the higher efficiency lamps (metal halide, high-pressure sodium, and low-pressure sodium) is not an appropriate application for most homes.
- These lamps may be considered for farms and businesses based on the areas to be illuminated. Some of these lamps provided rather distorted colors of the images and this may present a problem for workers and/or animals.
- The low-pressure sodium lamp (although the most efficient) produces the greatest distortion of colors and the objects being illuminated appear white, shades of gray, or black. Check with a lighting consultant and experiment yourself with several lamps before selecting the lighting system for a new or existing facility.