This article was originally published in the November/December 1994 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
| Home Energy Home Page | Back Issues of Home Energy |
Home Energy Magazine Online November/December 1994
Energy-Efficient Lighting for the Home
This guide can help consumers find their way through the wide array of energy-efficient lighting choices available today.
by Jeanne Byrne
The incandescent light bulb has been the proud symbol of good ideas since the time of Edison. Most of us have used these same pear-shaped A-lamp incandescents for as long as we can remember. Over the years they have helped us to cook, read, work, and play, and even have provided security and mood. But the standard A-lamp gets a D in energy efficiency when compared to new fluorescent (and some improved incandescent) energy-saving bulbs.
What are these energy-efficient light bulbs? How much energy do they save? What quality of light do they produce? How much do they cost? How long do they last? Where do you find them?
In the following pages we'll answer some common questions about energy-efficient light bulbs, and present the information you need to buy the best light bulbs for your home. As you read, note that the word lamp generally refers to the light bulb itself. When referring to fixtures, we will use more specific terms like table lamp.
What's Out There?
There are several incandescent bulbs that are more efficient and/or last longer than standard bulbs. Reduced-wattage light bulbs are 1%-5% more efficient than standard incandescents, but most of their potential for energy savings is from lower wattages (for instance, 67 watts instead of 75 watts). When substituted for the higher-wattage equivalents, the light output decreases, but not very noticeably. In effect, a 10%-15% energy savings can be achieved with these bulbs, although only a fraction of that savings is from greater efficiency. These lamps are sometimes marketed as energy-savers or watt-misers.
Try to avoid the so-called long-life incandescents. They do last a little longer because the filament operates at a lower temperature than in standard incandescents, but they produce less light and are less efficient.
Tungsten halogen (sometimes called quartz or quartz halogen) incandescents are more efficient than standard bulbs and last three to four times longer. The filament is enclosed in a quartz glass capsule with halogen gas. The gas reacts with the tungsten evaporated from the filament, then redeposits it, improving efficiency and lifetime. Unfortunately, many popular tungsten halogen fixtures use 300-watt or even 500-watt lamps--these certainly won't save energy compared to a 60-150-watt standard incandescent! Instead of buying these fixtures, look for A-line halogens to replace standard incandescents, and reflector halogens to replace standard flood and spot lamps.
Some halogens have an infrared-reflective coating (sometimes called HIR) that makes them even more efficient. These lamps are currently available only in reflector (flood and spot) versions.
Compact fluorescents use one-quarter to one-third as much electricity to give the same light output as a standard bulb, and last up to 10,000 hours, compared to 1,000 for the typical incandescent. Even most long-life incandescents would have to be replaced several times during the lifetime of a compact fluorescent.
Compact fluorescent bulbs and ballasts (for an explanation of ballasts see Lighting Basics) can be purchased either separately (modular) or as an integral unit (self-ballasted). The self-ballasted units are cheaper up front and more readily available. The advantage to buying ballast and bulb separately is that the ballasts have lifetimes ranging from 50,000 to 70,000 hours, several times the lifetime of the bulb. So you can replace just the bulb (by far the cheaper of the two parts) five to seven times, saving money and needless waste. Your choices in modular compact fluorescents may be more limited, however--only recently did units become available with electronic ballasts. It may also be difficult to find replacement bulbs (or impossible if the model is discontinued during the lamp's lifetime).
There are several different sizes and shapes of compact fluorescent bulbs--generally they consist of phosphor-coated tubes, folded or curled to increase the surface area. Quad tube lamps have two u-bent sections (not technically separate tubes, although that's what it looks like) and tend to have higher output than single twin tube models. New triple tube models have three tube sections to give higher light output from a shorter bulb. Sometimes you can see the tubes; on other lamps they are enclosed in a glare-reducing casing (cylindrical or globe-shaped) that makes them look more like large incandescents.
The circline is not technically a compact fluorescent. It's more like a linear tube bent into a circle. Circlines tend to have poorer color rendition (except some of the newer ones) but are available with higher light output then most true compacts.
All of these lamp types come in models that can screw into existing sockets. But you will get the most out of a compact fluorescent, circline or tungsten-halogen bulb if it's used in a fixture specially designed for the bulb's shape, size and temperature sensitivity. Installing a new fixture is a permanent retrofit--there's no standard Edison socket to screw a standard incandescent bulb into. The fixtures can be expensive but replacement bulbs are much cheaper than new screw-in lamps.
For many home lighting needs the most efficient light for the job is a linear fluorescent. Many people use them in bathrooms, kitchens and garages because a single fixture can brightly light a relatively large area. The most common of these linear fluorescents is the four foot T12 that we associate with offices. (T12 means that the diameter of the bulb is 12-eighths of an inch.) T8 lamps are more efficient--they are narrower (one inch in diameter) and most have better color rendition than the T12s. To replace a T12 lamp with a T8, you must buy a special ballast--for the highest efficiency, use an electronic ballast. You may have difficulty finding T8 lamps and ballasts in stores that cater to residential customers. Smaller (one or two feet long) T5 linear lamps can be mounted under cabinets or over sinks for efficient task lighting. All linear fluorescent fixtures need to be hard-wired by an electrician.
Flood and Spot Lamps
Reflector (flood and spot) lamps, used to illuminate outside areas around homes or highlight walls or artwork indoors, have reflective coatings to direct the light in a wide or narrow beam. The three major types are common reflector (R), parabolic aluminized reflector (PAR), and ellipsoidal reflector (ER). Many R and PAR lamps will be effectively banned by new efficiency standards that take effect November 1, 1995. The standard incandescent 75- and 150-watt PAR lamps most commonly used for outdoor area lighting are among those that will no longer be available. Good replacements for these include halogen PARs and compact fluorescent reflector lamps (make sure they are rated for outdoor use). Halogen PARs with an infrared (IR) coating are far more efficient than the standard halogen PARs.
Many people distrust compact fluorescent lights because they believe the quality of light will not be as good as that of an incandescent. The fears used to be justified--the cold-looking fluorescent tubes we know from office buildings, schools, and factories can appear stark and institutional--but the newer compact fluorescents and even the full-size tube models are looking better and better.
It may be surprising, but fluorescent lamps can recreate the warm feel of standard incandescent bulbs. Manufacturers use rare earth, tri-chromatic phosphors in these fluorescent tubes to produce better quality light and color rendition.
Which fluorescent lamp gives the most pleasing light? Your own taste will decide. From one fluorescent model to another you will find variation in the color of the light and the way objects look under it. Try to find a store that has the energy-efficient alternatives on display with the lamps turned on, or ask to see a particular light powered up. But even if you don't have the opportunity to see the light or to compare various models by sight, you can still get a sense of which light will look better. Two numbers are included in lamp specifications that tell us approximately what the light will look like. They are the correlated color temperature or CCT, and the Color Rendering Index or CRI (see Lighting Basics). Using the values for standard incandescents as a reference, you can compare these numbers to get a rough idea of the quality of light to expect. And you can choose a compact fluorescent with either warm or cool color temperature. (Linear fluorescents come in neutral, too.)
The quality of light given off by incandescents is not necessarily the most desirable type of illumination. One lighting scientist who has replaced the incandescent bulbs in his home with energy-efficient lights prefers the whiter light that he selected and believes the colors in his home are now more vibrant. Incandescent lighting looks dirty and too yellow to him now. When people first switched from candles and kerosene lamps to electric lights, the incandescent light surely must have looked unnatural. Yet from years of use, that light is now the standard. As compact fluorescents become more prevalent, they may replace incandescent lights as the glow of choice!
Flicker and Buzz
Do fluorescent lights flicker? The question is more complex than it may seem. Fluorescent lights need a ballast to operate and there are two kinds of ballasts--magnetic and electronic.
The glow from a fluorescent lamp with a magnetic ballast actually dims momentarily every 1/120th of a second because of normal oscillations in the alternating current. Although this variation is not actually visible as a flashing of the light, it may cause eye-strain, headaches, or other problems for some people. Fluorescent lights that clearly flicker even after they are warmed up, perhaps a few times per second or slower, are simply defective.
Compact fluorescents are much less likely than their full-sized relatives to present such problems. Using lamps with electronic ballasts eliminates the possibility of a flicker. These ballasts raise the frequency of the lamp current far above the rate of change that the eye can perceive.
Occasionally a magnetic ballast will emit an unnerving hum. This ballast is a piece of iron with wires wrapped around it and the electricity passing through the ballast can cause audible vibrations (often when the ballast is old and needs to be replaced). Electronic ballasts stay quiet because of their higher frequencies.
Compact fluorescent lights with magnetic ballasts may blink a few times when you first turn them on, and many models (including those with electronic ballasts) take up to a minute to come to full brightness. This doesn't mean they're defective. In fact, the bulbs that come to full brightness more slowly are likely to last longer, and will probably suit most of your lighting needs just as well.
Which One Goes Where?
Which lamps should you replace with energy-efficient bulbs? There are several factors involved in determining whether retrofit is appropriate for a given fixture.
How Much Are the Lights On?
You will save the most energy by replacing lights that are on many hours per day. A light that is on less than a couple of hours per day will take a long time to pay back the initial investment. For instance, if you have a 60-watt A-line incandescent closet light that is on only 5 minutes per day, the simple payback time (at an electricity rate of 8.7 cents per kWh) for a $19.00, 15-watt compact fluorescent replacement is 160 years! But use that same bulb five hours per day, and the payback falls to about two and a half years.
Most residential lighting fixtures in the United States are intended for standard incandescent lamps. While many compact fluorescent lamps are designed to screw into the same sockets, the bulbs tend to be bigger and heavier than the incandescents they replace. Because of this, ordinary incandescent fixtures are sometimes too cramped for some compact fluorescents. Choose the shape and size of the new lamp according to the fixture's dimensions.
If a fluorescent is too large to fit inside a lamp shade harp (the metal bracket that holds the shade above the bulb), harp extenders can be purchased at a hardware store that will solve the problem by both widening and heightening the space available for the bulb. Fortunately, the harp extenders are a one-time, small ($1-$2) investment. Some lamps arrive with plastic harp extenders in the package. One problem with harp extenders, however, is that they raise the lamp shade, which may partially expose the lamp to view.
A circular compact fluorescent may be the solution if the double or triple tube models are too tall for a lampshade. The harp fits between the ballast and the circular lamp, making the height unimportant, although you may still need harp extenders to widen the space for the ballast. Circular fluorescents are also available in higher wattages than the truly compact fluorescents, making it easier to replace incandescents of 100-watts or greater.
The extra weight of compact fluorescents may make some standing lamps too top-heavy or unbalance hanging fixtures. Newer compact fluorescents with electronic ballasts are smaller and lighter than magnetic models.
Location Can Affect Light Output
Even if a compact fluorescent and an incandescent bulb have the same rated lumen output (see Comparing Light Output), they may produce different amounts of light at the point of use, depending on the shape and color of the lamp shade or fixture lens. In general, light from fluorescents tends to be more diffuse than incandescents since light is emitted from the phosphors all along the bulb. Incandescents, with glowing filaments, are more of a point source. Also, when compact fluorescents are installed base down, the wide ballast blocks some of the light from shining directly underneath the bulb.
Reflectors are sometimes built into recessed can fixtures to direct more light out of them. These reflectors may be designed for a specific shape of bulb, as one energy-conscious homeowner discovered when he changed all the bulbs in recessed ceiling fixtures to tungsten-halogen bulbs. The new bulbs were more efficient than the previous ones but were also considerably shorter. Since the reflectors in the fixtures were designed to project light from a certain point in the bulb, using a shorter bulb drastically cut the light leaving the fixtures. In this case, the improvement in efficacy of the bulb was swallowed up in the greater loss of efficacy of the bulb and fixture together.
Another phenomenon not widely known is that the light output from (and thus the efficacy of) many compact fluorescents decreases when they are installed base-down instead of base-up. This means that if you put your compact fluorescent in a ceiling fixture hanging down, it may emit more light (lumens) than if you put the same lamp right-side up in a table lamp. The base-down lamp will still be more efficient than an incandescent, but you may need a higher-wattage compact fluorescent than you would choose from a simple comparison of rated lumen output. Circlines and certain shapes of compact fluorescents are less likely to have this problem. Once new labeling requirements go into effect, manufacturers will have to indicate whether the position of the bulb affects its light output (see New Labels).
Ambient Temperature and Humidity
Many fluorescent lamps are unsuitable for outdoor use in cold climates. They may not function at all at low temperatures because the ballasts won't start the lamp below a certain temperature. In this regard, electronic ballasts perform much better than magnetic ballasts. Typical magnetic ballasts won't start below 40deg.F; electronic ballasts function down to 0deg.F.
Cold can also affect the light output of the lamps. An exposed compact fluorescent at 0deg.F burns only faintly. If the bulb is housed in a sealed fixture, the lumen output will improve because the bulb will warm itself. Choosing a bulb with higher lumen output will help, both because the bulb is intended to produce more light and because it will heat the fixture to a higher temperature. Make sure an enclosed fixture has ventilation slots, however, because too much heat build-up can also affect the bulb's performance.
Look on the package to see if there are temperature and humidity restrictions on a particular light you want to buy. Generally, the newer models of compact fluorescents are less temperature-sensitive.
If a light is on a dimmer switch, fewer energy-saving retrofits can be used. In general, dimming rules out compact fluorescents, though a few exceptions are appearing on the market and are likely to become more common in the future.
If you have dimmable incandescent fixtures, adjusting the light level only as high as you need saves energy. But don't buy light bulbs that are brighter than you'll ever need at full power. You save more energy by replacing a 100-watt bulb with a 60-watt bulb than you do by dimming the 100-watt bulb to provide the lower light output.
Tungsten halogen incandescent bulbs will darken if they are always dimmed. Unlike most bulbs (incandescents and fluorescents), tungsten halogens maintain over 90% of their original lumen output throughout their lives. However, to do so they must operate at least part of the time at full power, so they can reach an adequate temperature for the bulb to be self-cleaning.
Even undimmed, some older models of tungsten-halogen bulbs that contain diodes may flicker noticeably. Some people can see a flicker at 60 times per second from these bulbs and may find it disturbing. Dimming the light makes the flicker more pronounced.
Keep in mind the accessibility of the light you are thinking of replacing. If it is difficult to reach, the importance of the lifetime of the lamp increases. Because of their long lifetime, compact fluorescents are a good retrofit for the lights that are both inaccessible and used many hours per day. Installing a compact fluorescent bulb can save you several trips up the ladder and awkward reaches. Don't be tempted by the long-life incandescent bulbs--they will cost more energy and money, because they are even less efficient than plain incandescents, and their lifetime is generally still quite short compared to compact fluorescents.
All fluorescent lights contain small amounts of mercury. The newer bulbs contain less, but mercury is essential to the operation of fluorescent lights. The mercury poses no threat while it's in the bulb, but it does cause an environmental hazard for disposal. If you break a bulb, try to avoid inhaling the mercury. Use a wet rag to collect the debris immediately and put it in a container with a lid for disposal. If you think you may have missed some, air out the room where the bulb broke.
Some compact fluorescents with magnetic ballasts also contain a small amount of short-lived radioactive isotopes. (Radioactive content will be listed on the label of any lamp that contains these elements.) The radioactivity would only be released if the lamp were completely crushed. Compact fluorescents with electronic ballasts, and most with magnetic ballasts, do not contain any radioactive materials.
As with any consumer product that contains hazardous materials, you shouldn't toss your old fluorescent light bulbs in the garbage. Find out if there is a recycling program for them in your community or, if necessary, dispose of them as hazardous waste with batteries, paints, and other household hazardous wastes.
Before condemning compact fluorescents on environmental grounds, consider that operating incandescent bulbs typically creates much more pollution from power plants (including mercury and long-lived radioactivity) than using the compact fluorescents that replace them.
Where do you find energy-saving lamps? Most stores that carry ordinary A-line incandescents, unfortunately, don't carry many energy-saving alternatives. You may see some reduced-wattage incandescent bulbs, but finding compact fluorescents and tungsten-halogens is not as easy.
Even if an energy-saving light bulb appears on the shelves of the local grocery store, check the yellow pages for a store that specializes in lighting to get a wider selection of brands and bulb types. It's easy to get dicouraged about compact fluorescents if your choices are limited to one or two models that don't fit in your fixtures or have poor color rendition. You can obtain a broad range of bulbs and fixtures by mail from catalog companies (see Mail Order Catalogs). Your utility may also offer rebates on lamps or fixtures, or even give away compact fluorescent bulbs.
Will My Utility Bill Be Lower?
Yes, but it may not be easy to observe due to fluctuations in electricity use patterns and length of meter-reading periods. The reduction will be most noticeable in cases where many lights, operating many hours per day, are replaced. Apartment building owners, for example, experience dramatic electricity savings after replacing incandescent bulbs in hallways with fluorescents. In addition, large cash savings are obtained in avoided purchases of new bulbs. In this section, we look more closely at costs and techniques for comparing the economics of different bulbs.
The purchase price of standard incandescent bulbs is considerably lower than that of energy-efficient lamps. However, the hidden costs of choosing incandescents--the long-term electricity costs and the costs of repeated replacements of these relatively short-lived bulbs--make standard incandescents more expensive over time. Even if you buy an energy-efficient lamp that sells for many times the price of the incandescent bulb (which they usually do), you will save money in the long run if the new lamp cuts electricity use enough and lasts long enough.
But what's enough? You can directly compare two bulbs that produce about the same amount of light but use different amounts of energy (different wattages) and last different amounts of time, by calculating the cost per 1,000 hours of use for each. This cost takes into account the purchase price of the lamp, the cost to operate it, and how long it lasts. If the bulb you are considering as a replacement gives a lower cost per 1,000 hours, then it's enough to save you money, no matter how much greater its purchase price may be. You can also use the purchase price and the savings per 1,000 hours to find out how many hours the compact fluorescent must be used before it will have paid for itself. This is called the simple payback time (see The Real Cost of Lighting).
When you examine a lamp package, put your greatest faith in solid facts like wattage, lumen output, and lifetime, rather than claims of percent of energy savings or dollars saved annually, which are meaningless unless you know the assumptions behind them.
Use Them Well and Wisely
As you seek out the best light bulbs for your home, consider that how you operate the lamps you install will probably make the biggest difference in your energy bill. Here are a few common-sense reminders:
How Light Is Produced
An incandescent lamp consists of a tungsten wire, or filament, encased in a glass housing. The filament heats up when electricity passes through it, just like the wires of a resistance heater do. In fact, ordinary bulb filaments are much more effective at producing heat than light. Most of the power to the bulb is wasted in radiated heat. (In commercial installations of many energy-efficient lamps, a secondary payoff is often a reduction in air-conditioning costs.)
Fluorescent lights work on a different principle. They contain two main parts: a lamp and a ballast. (Many compact fluorescents also have an adapter to enable them to be screwed into standard incandescent sockets. Often the ballast and adapter, or all three parts, are sold as an integrated unit). The lamp is filled with mercury gas that is ionized by electricity passing through it. The ionization generates ultraviolet light. The inside surface of the glass envelope is coated with phosphors--substances that give off a visible glow when bombarded with ultraviolet light. Fluorescent lights create much less waste heat for the amount of visible light they produce than do incandescents.
The ballast converts ordinary household 120V current to the high voltage needed to ionize the gas in the lamp. Then, once the lamp is aglow, the ballast limits the amount of current that flows through the lamp, since less is needed to maintain the process once it has started up. Magnetic, or core-coil ballasts, consist of loops of wire tightly wound around an iron core. Lamps with magnetic ballasts will flicker briefly when turned on. Solid-state electronic ballasts operate the lamp at a much higher frequency, start up immediately and are not as heavy as the magnetic ballasts.
The most familiar rating of a light is its input power, measured in watts. Visible light output is measured in lumens and the ratio of the number of lumens given off to the number of watts consumed is called the efficacy. The efficacy is a handy number for comparing the relative energy-efficiency of different lamps or lighting options. Efficacy is analogous to unit-pricing, which allows simple cost comparisons of different products even though their package sizes aren't identical. Higher efficacy means a more efficient product.
Two numbers that tell us about light quality are the color rendering index, or CRI, which is on a scale up to 100, and the correlated color temperature (CCT), expressed in the Kelvin (deg.K) temperature scale. Color temperature tells us how the light itself will look. Lights with color temperatures higher than 2,800deg.K, ironically called cooler lights (because they are bluer), look whiter than standard incandescents. Temperatures lower than 2,800deg.K make the lights warmer; that is, they appear more reddish.
As for the objects the light illuminates, CRI gives the clue. CRI values in the 80s and 90s indicate color rendering ability quite close to standard incandescents. The object will look natural or normal to someone accustomed to standard incandescent bulbs. If you choose lights with lower CRI values, be prepared for objects to take on an abnormal appearance. For reference, the older fluorescent lamps common in offices have a cool color temperature of about 4,000deg.K and a CRI in the 60s.
COMPARING LIGHT OUTPUT
The table below presents the wattage and rated light output of common incandescents and their nearest equivalents. These numbers don't tell the whole story--many factors affect a lamp's actual light output, including the characteristics of the fixture and sometimes even the lamp's positioning. Light output will also vary between different models with the same wattage, so be sure to check the package for a particular lamp's rated lumen output. The light output of both incandescent and fluorescent lamps decreases as they age.
Household Lamps Standard Compact fluorescent Reduced-wattage Tungsten halogen incandescent and circline* incandescent incandescent watts (lumens) watts (lumens) watts (lumens) watts (lumens) 25 (220) 5 (210-250) -- -- 40 (460-505) 7 (400) 34 (410) 42 (665) 60 (870-890) 13 (700-900) 52 (800) 52 (885) 75 (1,190-1,220) 18 (1,100-1,250) 67 (1,130) 72 (1,090-1,300) 100 (1,750) 27 (1,550-1,800) 90 (1,620) 100 (1,600-1,880) 150 (2,850) 32 (1,800-2,100) 135 (2,580) --
Flood Lamps Standard Infrared-reflective Compact incandescent Tungsten halogen tungsten halogen fluorescent PAR 38 PAR 38 PAR 38 reflector lamp watts (lumens) watts (lumens) watts (lumens) watts (lumens) 75 (750-765) 90 (1,270) 60 (1,150) 18 (800)* Wattages shown are for lamps only (ballast wattage is not included).
Sources: The Lighting Pattern Book for Homes, Russell P. Leslie & Kathryn M. Conway, Lighting Research Center, Rensselear Polytechnic Institute, Troy, NY, 1993.
Advanced Lighting Guidelines, 2nd Ed., California Energy Commission, Sacramento, CA, March 1993.
Fluorescent retrofits often do not achieve their given ratings for operating hours and light output. This is partially due to the lighting industry's meaning of a bulb's rated life--the number of hours of operation at which 50% of a tested sample of bulbs have burned out. Fluorescents under test are turned on for three hours and then off for 20 minutes in a continuous cycle. Incandescents, since they suffer less wear from each on-off transition, are left on 23 hours daily during testing. In many homes, fluorescent lamps are typically on less than three hours per start, so the bulbs' actual lifetimes are often lower than their ratings.
CHOOSING THE BEST LAMP FOR THE JOB
Efficacy Lifetime CRI Typical price (lumens/watt) (hrs) (color rendering index) per lamp** Standard incandescent (40-100 watts) 12-18 750-1,000 95+ $.75 Long-life standard incandescent (52-90 watts) 13-15 2,500 95+ $1.00-$1.50 Reduced-wattage incandescent (52-90 watts) 15-18 750-1,000 95+ $1.00 Tungsten-halogen incandescent A-lamp (40-100 watts) 16-19 2,250-3,500 95+ $4.00 Compact fluorescent* (5-27 watts) 35-60 7,500-10,000; 50-90 $6.00-$19.00 reusable ballasts can (includes ballast) last 50,000 to 70,000 Circular fluorescent screw-ins* (20-32 watts) 30-50 12,000 50-90 $7.00-$11.00 (includes ballast) 4-Foot linear fluorescent T-12* (40 watts) 62-80 20,000 62-70 $2.00-$6.00 4-Foot linear fluorescent T-8* (32 watts) 78-92 20,000 70-80 $5.50-$7.00 * Efficacy takes into account added energy use of ballasts.
** Prices may vary widely.
Sources: The Lighting Pattern Book for Homes, Russell P. Leslie & Kathryn M. Conway, Lighting Research Center, Rensselear Polytechnic Institute, Troy, NY, 1993. Advanced Lighting Guidelines, 2nd Ed., California Energy Commission, Sacramento, CA, March 1993.
Effective May 1995, all light bulb manufacturers will need to relabel their products to comply with new Federal Trade Commission rules. The new labels will include the lamp's rated lumens, watts and lifetime. For incandescent reflector lamps, light output must be given at beam spread and so indicated on the label. Also, if positioning affects a compact fluorescent's light output by more than 5%, it must be disclosed.
THE REAL COST OF LIGHTING
Use this worksheet to calculate the total cost per thousand hours of using any light bulb you are considering buying. The calculation accounts for the purchase price, energy cost and lifetime of the lamps. Compare the total cost per 1,000 hours to determine which option will cost less in the long run.
Example: Example: COST PER 1,000 HOURS 60 watt 18 watt Incandescent Compact Fluorescent (1) What price do you pay for $_____/kWh $ 0.09 /kWh $ 0.09 /kWh electricity per kilowatt-hour? (2) What is the wattage of the bulb? _____ watts 60 watts 18 watts (3) Multiply (1) by (2): $_____/kWh 2 _____ watts = $_____/1,000hrs $ 5.40/1,000hrs $ 1.62/1,000hrs (4) What is the rated lifetime of _____ hours 1,000 hours 10,000 hours the bulb? (5) Divide (4) by 1,000: _____hours / 1,000 = _____ 1 10 (6) What did you pay for the bulb? $_____ $ 0.75 $ 15.00 (7) Divide (6) by (5): $ _____ / _____ = $_____ $ 0.75 $ 1.50 (8) Add (3) to (7): $_____ + $_____ = $_____/1,000hrs $ 6.15/1,000hrs $ 3.12/1,000hrs Total Cost per 1,000 hours $___________ $ 6.15 $ 3.12 Since many compact fluorescents come as separate lamps and ballasts, you should add the prices for all the components into the purchase price. SIMPLE PAYBACK PERIOD Use this calculation to find out how quickly a replacement light bulb will repay its purchase price with energy savings.
Example: Replacing a 60 watt incandescent bulb with an 18 watt compact fluorescent (9) Purchase price for new $_____ $15.00 efficient bulb (10) Difference in energy cost $_____ $5.40 - $1.62 = $3.78 per 1,000 hours, from (3) above (11) Divide (9) by (10) and multiply by 1,000 hours: $_____ / $_____ x 1,000 hours = _____ hours 3,968 hoursIn this example, the $15.00 purchase price of the 18 watt compact fluorescent to replace the 60 watt incandescent would be paid back in saved energy costs in about 4,000 hours of use. Also, during that time, you would have avoided purchasing three incandescents at 75 cents each, and the new bulb would continue to save both energy costs and incandescent replacement costs for about 6,000 more hours of use.
MAIL-ORDER LIGHTING CATALOGS
Mail-order companies carry a larger selection of efficient lighting products than you typically find in local stores. Call or fax them for a catalog.
Alternative Energy Engineering P.O. Box 339 Redway, CA 95560 (800)777-6609 Fax: (707)923-3009
Energy Answers P.O. Box 24 Lake Bluff, IL 60044 (800)762-7325 Fax: (708)234-1431
Energy Federation, Inc. 14 Tech Circle Natick, MA 01760 (800)876-0660
Fowler Solar Electric, Inc. 226 Huntington Road P.O. Box 435 Worthington, MA 01098 (413)238-5974 Fax: (413)238-0203
Greater Goods 515 High Street Eugene, OR 97401 (503)485-4224 Fax: (503)485-8253
Lo-Volt Lighting 606 West 184th Street Gardena, CA 90248 (213)321-9693 Fax: (310)323-3907
Real Goods 906 Mazzoni Street Ukiah, CA 95482 (800)762-7325 Fax: (707)468-9486
S & H Alternative Energy RD 3, Box 312 Putney, VT 05346 (802)722-3704 Fax: (802)722-3704
Seventh Generation 49 Hercules Drive Colchester, VT 05446 (800)456-1177 Fax: (800)456-1139 or (802)655-2700
Related ArticlesBright Prospects for Lighting Retrofits (Hasterok) Fixing the Fixtures (Siminovitch and Mills) How to Keep 'Em Down Home in the Socket (Manclark) Lighting Makeovers: The Best is Not Always the Brightest (Conway) Putting Energy-Efficient Lighting in Its Place (Polsby) Remodeling Bathrooms: Let the Energy Savings Flow (Johnston) Remodeling Kitchens: A Smorgasbord of Energy Savings (Sullivan) Steps to Successful Lighting Programs (Fernstrom) Training Guide for 'Total Comfort' Professionals Understanding Power Quality (De Almeida) What to Do when the Lights Go Out (Polsby) Whatever Happened to the E-Lamp? (Atkinson)
| Back to Contents Page | Home Energy Index | About Home Energy | | Home Energy Home Page | Back Issues of Home Energy |
- FIRST PAGE
- PREVIOUS PAGE