11:38 AM EST on Monday, November 21, 2005

BY TIMOTHY C. BARMANN
Journal Staff Writer

Part seven of a series

Thomas Edison may have been a genius, but one of his most enduring inventions -- the light bulb -- is one of today's biggest wasters of energy.

Bracing for Winter

Hear and see more from Journal writer Tim Barmann

Keep up with the weekly multimedia series on how to cut home heating costs...

Only 5 percent to 10 percent of the electricity that powers traditional bulbs actually goes toward producing light. The rest is converted into heat.

Since about 20 percent of a typical household's electricity bill goes toward lighting, this represents a big source of waste.

Fortunately, there's an easy and cost-effective way to trim lighting costs: replace old bulbs with energy-efficient compact fluorescent bulbs.

These bulbs, which screw into traditional light sockets, use up to 75 percent less energy and can last up to 10 times longer than a traditional incandescent bulb, according to the Energy Star Web site of the Department of Energy.

Some simple math shows how cost-effective replacing these bulbs can be. A standard 60-watt incandescent bulb that's on for five hours a day will use $15.51 in electricity over the course of a year, based on the rates of National Grid, the main distributor of electricity in Rhode Island.

By contrast, a 15-watt compact fluorescent bulb, which gives off the same amount of light, would use only $3.81 a year in electricity, if kept on for five hours a day. By replacing six lights, your electric bill would be cut by $5.80 a month, or $70 a year.

Businesses and schools adopted fluorescent lights many years ago. But homeowners have been resistant because they like the warm, pleasing light given off by traditional bulbs. But newer compact fluorescent bulbs are now made that give off a warmer cast.

And until recently, compact fluorescent bulbs were expensive, costing $10 each or more. But prices have dropped dramatically over the past couple of years and the bulbs can now be found in discount stores, such as Building 19 or Benny's, for as little as 50 cents to $2 each.

They come in a variety of shapes, including some that are designed to look like traditional bulbs. Some even have reflectors so they can be used in place of outdoor spotlights.

Unfortunately, labeling on light bulbs can be confusing, leading to questions such as how a 15-watt fluorescent bulb can give off as much light as a 60-watt traditional one.

The answer lies with the common mistakeof associating wattage with brightness. A light bulb's wattage is a measure of how much energy it uses, rather than how much light it gives off. To measure brightness, newer bulbs are often labeled with how many "lumens" they give off.

A fluorescent bulb rated at 15 watts gives off about 900 lumens, about the same amount as a 60-watt incandescent bulb.

Another way to cut down on lighting costs is to replace traditional night-lights with the thin, electroluminescent type that plug directly into an outlet. They look like miniature flat-screen TVs and usually give off a green or blue glow.

These night lights typically use .03 watts of electricity, compared with 4 watts for a standard night-light. That's 99 percent less electricity.

Tips for buying compact fluorescent lights can be found at:

http://www.eere.energy.gov/femp/technologies/eep(underscore)compact(underscore)fluor(underscore)lamp.cfm

But as efficient as fluorescent bulbs are, new technology may eventually make them obsolete.

Developments in the semiconductor industry have led to advances in light emitting diodes, or LEDS, as a new lighting source.

These tiny lights, which are found in many appliances as a power indicator, are now being used in flashlights, traffic lights, store signs and a host of other applications.

Typically, several LEDs are bunched together to increase light output.

LED lights are said to be even more energy efficient than fluorescent lights, and they'll last longer.

But they are still relatively expensive, so it may be some time before they become a mainstream household lighting source.

Some companies now sell Christmas lights made from LEDs. A string of 100 mini LED lights was selling at an online store last week for $17.95. A similar string of traditional mini-bulb lights might run only $2.

The store advertises the lights as using 99 percent less electricity.

Timothy C. Barmann covers energy issues, utilities and technology. He can be reached at tbarmann@projo.com