Better lighting with less energy

The lighting section of a typical hardware store now contains a bewildering selection of light bulbs in various shapes, sizes, types, light colors and energy usage amounts.  But the average homeowner should be choosing between three types of light bulbs: incandescent, compact fluorescent (CFL) and light-emitting diode (LED).  Most light bulbs currently available are these types. 

There are four primary considerations when deciding which light bulbs to purchase.

Bulb wattage:
  The wattage of the bulb indicates how much energy the bulb uses.  The wattage used to also be a measure of the amount of light a bulb produced.  With the advent of CFL and LED light bulbs, lumens began to be more widely used as a measure of the amount of light a bulb produced.  This was necessary because CFL and LED bulbs use far less energy (wattage) to produce the same amount of light (lumens) as an incandescent bulb.

Lumens:  This is a measure of the amount of light produced by a bulb, or the brightness of a bulb.  It’s hard for me to adjust to using lumens instead of watts, because I have a sentimental attachment to the term watts as an indication of brightness.  Throughout my life, I’ve been told by numerous woman that I look best in very low wattage lighting.

Estimated life of a bulb:  This is usually measured in hours.  It’s an important number to know for understanding the costs associated with replacing bulbs.   All light bulbs fail or “burn-out”.  Some just do so much quicker and more frequently than others.  The life of  individual bulbs can vary from the estimated bulb life.   Incandescent bulbs have an estimated life of between 750 and 1,000 hours,  CFL bulbs have an estimated life between 6,000 and 15,000 hours, and LED bulbs have an estimated life between 25,000 hours and 50,000 hours.

Light color:  Light color is measured on the Kelvin scale.  A lower number on the Kelvin scale means a more yellow (or warmer) light.  A higher number on the scale means a whiter (or cooler) light.  The Kelvin scale ranges from 1,000 degrees  (reddish-orange color) up to 8,000 degrees (bluish-white color).  On this scale, degrees is a measure of light; it has nothing to do with heat.  Incandescent bulbs have a light color range on the Kelvin scale from about 2,700 to 3,200 degrees.  CFL bulbs have a light color range on the Kelvin scale from about 2,700 to 6,500 degrees.  LED bulbs have a light color range similar to CFL bulbs.

Light bulb basics:

Incandescent light bulbs:  Incandescent bulbs have been around for over 125 years.  Incandescent bulbs work by electricity heating the metal (tungsten) filament to a temperature where it glows.  Obviously, a light bulb that produces light by heating a metal strip so much that it glows is a lot better at producing heat than producing light.  The bulbs also get dimmer over time because the heat of the filament vaporizes the tungsten, which coats the inside of the bulb with a dark film.   Halogen bulbs are similar to incandescents, except the tungsten filament is encased in a glass tube.

CFL light bulbs:  The spiral-shaped CFL bulb that can be screwed into regular light fixtures was invented by a General Electric engineer in 1976.  CFL bulbs work from an electric current electrifying the argon and mercury gases in the bulb.  CFL bulbs use less than one-fifth of the energy of incandescents and typically last 8 to 15 times as long as incandescents.   

The EPA Energy Star program recommends that fixtures containing CFL bulbs be left on when leaving a room for less than 15 minutes, because frequently turning a CFL bulb on and off will dramatically shorten the lifespan of the bulb.

LED light bulbs:  The first visible-spectrum LED was developed by General Electric in 1962.  LED bulbs were originally used as a long-lasting, energy-efficient, solid state component for electric equipment.  The technology has been steadily improved over the years.  LED bulbs use less energy than incandescent bulbs and CFL bulbs, and last much longer than either of them. 

Light bulb economics:

I think we can all reasonably agree that incandescent bulbs are cheaper to purchase than CFL and LED bulbs.  A CFL bulb can cost $3 to $4 more than an incandescent bulb and and a LED bulb can cost $18 to $29 more than an incandescent bulb.

But before you get sticker shock on the initial purchase price, it’s important to consider it within the overall costs of the bulbs.  Buying CFL and LED bulbs should be thought of as investments with long-term payouts in lower energy costs and fewer bulb replacements.

Remember the estimated bulb lifespan ranges noted earlier in this article: incandescent bulbs typically last between 750 and 1,000 hours, with a range midpoint of 875 hours; CFL bulbs generally last between 6,000 and 15,000 hours, with a range midpoint of 10,500 hours; LED bulbs typically last between 25,000 and 50,000 hours, with a range midpoint of 37,500 hours.

Using those range midpoints, CFL bulbs could be expected to last 12 times longer than incandescent bulbs.  Buying the additional 12 bulbs at a cost of $0.50 each is $6 in replacement bulb costs.

LED bulbs could be expcted to last a whopping 43 times longer than incandescent bulbs.  Buying the additional 43 bulbs at $0.50 each is $21.50 in replacement bulb costs. 

And the energy savings during the life of those bulbs is even more dramatic. Using an electricity rate of $0.086 per kWh, a CFL bulb might be expected to save $43 in electricity costs.  Using the same rate, a LED bulb might be expected to save a stunning $163 in electricity costs. 

The approximate total energy savings and bulb replacement savings that could be anticipated from the purchase of each bulb is:  CFL bulb: $49, and LED bulb $184.  Wouldn’t you put your money in an investment that provided that kind of return?  

Technology has provided us an opportunity to buy light bulbs that use a fraction of the energy of the old, incandescent light bulbs, need far fewer replacements and are available in a much broader range of light colors.  Perhaps unsurprisingly, consumer demand for incandescent bulbs has dropped 50% in the past 5 years as people have figured out the benefits of CFL and LED light bulbs.

About the Author

Mark H. Witte is a strong proponent for energy efficiency and renewable energy, and believes individuals should have more control over how the energy for their homes is produced.