The Fluorescent Lighting System

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Section 8: Fluorescent Lighting Energy Savings and Product Comparisons

Fluorescent Light Efficiency Versus Incandescent

Here is the answer: Fluorescent lighting produces more light, consumes less power, and lasts longer than incandescent lamps. If the lamp wattages are identical (which means that consume the same amount of power), a fluorescent lamp can produce five times more light and still last eight to thirty times times longer than an incandescent lamp.

The problem, or problems that have caused consumer resistance to using fluorescent lighting are about as resolved as they will ever be. Key improvements made since 1995 include:

The most significant remaining problem is initial cost. The typical purchaser still has a hard time grasping the long-term cost savings in both electricity and lamp life that flourescent lamps provide, and so the buyer tends to only consider the purchase price. When you do consider these "big picture" items, the fluorescent lamp is the big winner.

Is the flourescent light the most efficient system available? No. Light Emitting Diodes (LEDs) are the most power-efficient lighting system available, found today in some traffic signal heads and holiday lighting as well as electronic equipment. However, for use as a general lighting system, LEDs currently have a high initial cost. The cost is expected to improve dramatically in the next several years. Until then, flourescent lighting is where the cost savings are.

To demonstrate, here are some bare facts on a few types of competing types of lamps:
(background colors in this table represent lamps of similar categories, not the color of light produced by the listed lamp)

Lamp Example Lamp Type Power Consumed Per Lamp (in Watts) Light Produced
(in Lumens)
Average Initial Cost (US) Average Life Per Lamp (in Hours) Power Cost per 24 hours of use (Assuming $0.12 US per /KWH) Cost to Own and Operate for 20,000 hours
#1 Screw-in Incandescent 60 800 $0.60 1,000 $0.1728 (20 new lamps X $0.60) + $144 power = $156 US
#2 Screw-in Compact Fluorescent (CFL) Warm White (2670K) 13 900 $2.50* 10,000 $0.03744 (2 new lamps X $2.50) + $31.20 power = $36.20 US
#3 Screw-in Incandescent Halogen (Clear Glass) 60 900 $3.00 3,000 $0.1728 (7 new lamps X $3.00) + $144 power = $165 US
#4 Screw-in Compact Fluorescent (CFL) Warm White (2600K) 23 1600 $4.00* 8,000 $0.06624 (3 new lamps X $4.00) + $55.20 power = $67.20 US
#5 Screw-in Compact Fluorescent (CFL) Warm White (2700K/82CRI) 26 1580 $5 10,000 $0.07488 (2 new lamps X $5) + $62.40 power = $72 US
#6 Screw-in Incandescent 40 490 $0.60 1,000 $0.1152 (20 new lamps X $0.60) + $96 power = $108 US
#7 Traditional Four Foot Fluorescent Warm White or Cool White 40 3200 $4.00 20,000 $0.1152 (1 new lamp X $4.00) + $96 power = $100 US
#8 Screw-in Incandescent Halogen PAR 38 Flood 100 1,400 $5.00 2,000 $0.288 (10 new lamps X $5.00) + $240 power = $290 US
#9 Screw-in Compact Fluorescent PAR 38 Flood 23 1,300 $5.00* 6,000 $0.06624 (4 new lamps X $5.00) + $55.20 power = $75.20 US
(Information on printing color tables on color printers can be found here.)

Lamp #2 (13 watt compact fluorescent) in the table above produces a little more light than Lamp #1 (traditional 60 watt incandescent), Lamp #2 lasts ten times longer than Lamp #1, and Lamp #2 costs less than 25% of what it costs to operate the Lamp #1. Lamp #2 also generates less heat than Lamp #1, which can also reduce air conditioning costs.

Lamp #3 (60 watt incandescent lamp with halogen) produces more light than lamp #1 and the same amount of light as #2, and lamp #3 has longer life than normal incandescent lamps, but produces less light than lamp #4 (23 watt compact fluorescent) or lamp #5 (26 watt compact fluorescent) and lamp #3 won't last as long. Halogen incandescent lamps do produce a "whiter" light than normal incandescent lamps, and in situations where more light is needed and fluorescent lamps cannot be used (such as on magnetic dimmers or emergency power circuits), halogen incandescent lamps are a possible solution. Be aware that halogen incandescent lamps are the most expensive lamps available (considering purchase price with operating costs) for the light produced.
Tip: If you are stuck using incandescents in certain fixtures and the fixture has a lamp shade or contains frosted glass, consider using unfrosted incandescent lamps. Unfrosted incandescent lamps emit 10-20% more light than frosted ones, and if used in a fixture where the bulb is obscured, take advantage of the extra amount of light you will get, and no one will know that the lamp isn't frosted. You may even be able to use a lower wattage lamp and save some energy.

Lamp #4 (23 watt compact fluorescent) produces considerably more light than Lamp #1 (60 watt incandescent) and still consumes about a third of the electricity. Currently, this is my favorite lamp size to use in place of 60 watt incandescents. It can also brighten-up a light fixture that could not use a 75 watt or larger incandescent, but if the compact fluorescent lamp will physically fit, it is an excellent substitute. Highly recommended for use in bedrooms, closets and hallways that are currently lit with one to three 60 or 75 watt incandescent lamps.

Lamp #6 (40 watt traditional incandescent) and lamp #7 (40 watt fluorescent lamp), both consume the same amount of power, but the fluorescent lamp produces over six times the amount of light for the same electrical cost. You would also have to purchase and install 20 incandescent lamps to last as long as the one fluorescent lamp, making the cost savings of using fluorescent lighting that much greater.

Indoor/Outdoor flood lamps #8 and #9 produce about the same amount of light, but the compact fluorescent lamp lasts about three times longer and costs 25% of what the incandescent lamp costs to own and operate. The Incandescent lamp is superior for producing a more focused light (despite being a "flood" lamp), and the incandescent offers "instant on" total brightness (not all compact fluorescents provide full brightness when turned on), but if you do not need either of these things, the compact fluorescent flood is very servicable alternative to incandescent flood lamps.

Note: Some Compact Fluorescent Lamps (CFLs) have some limitations that should be considered. Some lamp models are physically larger than the incandescent lamps they are meant to replace, some take minutes before they reach the operating brightness EACH time you turn them on, and prices on identical lamps vary significantly depending on where you buy them and in what quantity. These and other issues related to Compact Fluorescent Lamps are discussed in Section 7: Compact Fluorescent Lighting.

* The lamp prices shown are a very rough average taken between chain retail stores and "wholesale club" stores. The lowest costs with the smallest selection can be found at the "wholesale club" stores. For example, Lamp #2 above is sold in 8-packs at "Costco" for $12.72 US, or $1.59 US per lamp. Lamp #4 is sold in 4-packs at "Costco" for $10.59 US, or $2.48 US per lamp. Lamp #9 is sold in 3-packs at "Costco" for $14.98 US, or $4.99 US per lamp.

Identical or virtually identical lamps are also sold at Home Depot/Lowes in smaller quantities (including quantity one packaging) for prices between two and three times the Costco quantity price, and you may be offered a choice of light shades while the "wholesale clubs' usually offer only one light shade. The prices at Walmart or Target are perhaps two times higher than the Lowes/Home Depot price. When possible, always buy fluorescent lamps in quantity to save money. (Prices updated 7-Feb-2005)

To calculate power costs youself, use this formula:

(watts of lamp divided-by 1000) times 24 hours times cost of electricity per KWH
For example, if your area electricity costs are $0.12 per KWH and you want to know how much it will cost to run a 75 watt lamp (of any type) for 24 hours, the cost would be (75 / 1000) x 24 x 0.12) == $0.216, or 21.6 cents per day.

You can then multiply that figure ($0.216) by 30 for the average number of days in a month, and you have $6.48 to run that 75 watt lamp continuously for a month.

By comparison, a 17 watt compact fluorescent lamp that would produce more light than a 75 watt incandescent would cost 4.9 cents a day to operate, or a $1.47 a month, if you left it on all the time.

The higher the cost of electricity, the less significant the initial cost of buying fluorescent lamps becomes.

Fluorescent Light Efficiency and Marketing Trickery

Without a doubt, a fluorescent light is more efficient than any incandescent system available, including those using halogen or other gas invasion-fighting methods. (The smallest gas atoms are able to seep into incandescent light bulbs right through the glass, greatly reducing the lamps operational life, so a gas that won't react with the burning filament is placed in the lamp under high pressure to keep other gasses from migrating into the bulb, or as some lamp makers prefer to call it, the "capsule".)

However, just because a fluorescent lamp is 48 inches long and 1.5 inches in diameter doesn't mean it consumes 40 watts or produces 3200 lumens of light. (It used to, but not any more.) The lowest cost 48" fluorescent lamps may still consume 40 watts, but produce half of the light of a lamp that costs a little more to initially purchase. (The same problem of low quality lamps also exists for incandescent lamps, with a standard 60 watt incandescent lamp producing anywhere from 900 down to 450 lumens, depending on how poorly made the lamp is.) Always check the watts and lumens rating when buying any type of lamp!

Then there are the so-called "energy saving" 34 watt lamps that might only produce 50% to 66% of the light of the best 40 watt lamps, while only saving 15% of the electricity. That reduction of light may be so significant as to cause additional fixtures to be installed to compensate for the low light levels, completely defeating the energy savings of using these lamps with lower light quality and quantity in the first place. Also, some energy-saving lamps only last half as long as other models, increasing the cost of ownership. (Having been the victim of a couple of building-wide conversions from 40 watt lamps to 40 watt lamps with 34 watt "power-saver" devices, then to 34 watt lamps with the "power-saver" devices removed, the expense and hassles were simply not worth it, and the lower light levels caused many complaints. Executive office areas had to be re-lamped at the full 40 watt level so that they would stop complaining.)

These variations in power consumption, light quality and quantity, and operating life all mean that you have to be alert when selecting fluorescent lamps and make sure you are getting the lamp with the maximum amount of light that you want in the color shade that you want.

Fluorescent Light Efficiency (straight-line lamps)

The following table contains some lamp models from various vendors. Note that for the same color shade there are substantial differences in the amount of light generated between models of lamps, even though the lamps consume the same amount of electricity.

This is by no means a complete list of all available lamps in this category. Also, if a manufacturer made it hard to collect all the shown information on their lamps, lamps from that maker were not listed.

Lamp listings are divided by lamp color temperature and by power consumed. In each category, lamps are sorted by lumen output. This means that the lamps that generate the most light for the smallest amount of power consumed in a given color category appear first. Retail price was not considered.

The background color for each entry is an exaggerated indication of the color temperature of the lamps.

Lamp Maker Model Name Part Number Color Temperature and Color Rendition Index, See Note 1 Average Life (in Hours) Power Consumed (in Watts), See Note 2 Light Produced (in Lumens), See Note 3 Percent of the light compared to the brightest lamp, See Note 4

Warm White Lamps that consume 40 watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Sylvania Designer Warm White Plus F40/DWWP 3,000K (80) 20,000 40 3,300 100%
Philips Advantage F40T12/ADV30/
3,000K (85) 20,000 40 3,250 98.5%
Sylvania Designer Warm White F40/DWW 3,000K (80) 20,000 40 3,200 96.9%
Sylvania Warm White Plus F40/WWP 3,000K (70) 20,000 40 3,000 91%
Philips Home Light Warm Deluxe F40/HL WX/
3,000K (85) 20,000 40 2,970 90%
Philips Kitchen & Bath F40/KB/
3,000K (85) 20,000 40 2,970 90%
Philips Ultralume F40/30U/
3,000K (85) 20,000 40 2,970 90%
Philips SPEC F40/SPEC30/
3,000K (70) 20,000 40 2,880 87%
Sylvania Warm White Deluxe F40/WWX 3,000K (85) 20,000 40 2,130 64%
Philips Advantage F40T12/ADV35/
3,500K (85) 24,000 40 3,250 98.5%
Philips Ultralume F40/35U/
3,500K (85) 20,000 40 2,970 90%
Philips SPEC F40/SPEC35/
3,500K (73) 20,000 40 2,880 87%
Philips Home Light Warm F40/HL Warm/
3,500K (73) 20,000 40 2,880 87%
Philips Natural F40/N 3,700K (90) 20,000 40 1,870 56.7%

Cool White Lamps that consume 40 watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Sylvania Designer Cool White Plus F40/DCWP 4,100K (80) 20,000 40 3,300 100%
Philips Advantage F40T12/ADV41/
4,100K (85) 24,000 40 3,250 98.5%
Sylvania Designer Cool White F40/DCW 4,100K (70) 20,000 40 3,200 96.9%
Sylvania Cool White Plus F40/CWP/CVP 4,100K (70) 20,000 40 3,000 91%
Philips Ultralume F40/41U/
4,100K (85) 20,000 40 2,970 90%
Philips SPEC F40/SPEC41/
4,100K (70) 20,000 40 2,880 87.3%
Philips Home Light Cool F40/HL Cool/
4,100K (70) 20,000 40 2,880 87.3%
Sylvania Cool White Deluxe F40/CWX 4,100K (87) 20,000 40 2,250 68%
Philips Deluxe Cool White F40/CWX/
4,200K (89) 20,000 40 1,800 54.5%

Full Spectrum Lamps that consume 40 watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Philips Advantage F40T12/ADV50/
5,000K (85) 24,000 40 3,250 100%
Philips Ultralume F40/50U/
5,000K (85) 20,000 40 2,950 90.8%
Sylvania Sunstick F40/Sunstick 5,000K (90) 20,000 40 2,200 67.7%
Philips Colortone 50 F40/C50 5,000K (85) 20,000 40 1,915 58.9%

Daylight Lamps that consume 40 watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Sylvania Daylight F40DX 6,500K (88) 20,000 40 2,180 100%
Philips Daylight Deluxe F40/DX/
6,500K (84) 20,000 40 2,025 92.9%

7500K Lamps that consume 40 watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Philips Colortone 75 F40/C75 7,500K (95) 20,000 40 1,720 79%

Warm White Lamps that consume 34 or fewer watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Philips Ultralume F34/30U/RS/
3,000K (85) 20,000 34 (85%) 2,600 100.0% (78.7%)
Philips SPEC F34/SPEC30/RS/
3,000K (70) 20,000 34 (85%) 2,520 96.9% (76.4%)
Sylvania Warm White Super Saver F34/WW/SS/ECO 3,000K (52) 20,000 34 (85%) 2,365 91% (71.7%)
Philips Warm White Energy Saver F34/WW/RS/
3,000K (53) 20,000 34 (85%) 2,350 90.4% (71.2%)
Philips Ultralume F34/35U/RS/
3,500K (85) 20,000 34 (85%) 2,600 100% (80%)
Philips SPEC F34/SPEC35/RS/
3,500K (73) 20,000 34 (85%) 2,520 96.9% (77.5%)
Sylvania White Super Saver F34/W/SS 3,450K (57) 20,000 34 (85%) 2,365 91% (72.8%)

Cool White Lamps that consume 34 or fewer watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Sylvania Cool White Energy Saver F40/CW/SS/
4,200K (62) 20,000 34 (85%) 2,650 100% (80%)
Philips Ultralume F34/41U/RS/EW/
4,100K (85) 20,000 34 (85%) 2,600 98% (78.8%)
Philips SPEC F34/SPEC41/RS/
4,100K (70) 20,000 34 (85%) 2,520 95% (76.4%)
Philips Lite White F34/LW/RS/
4,200K (51) 20,000 34 (85%) 2,400 90.6% (72.7%)
Philips Cool White F34/CW/RS/
4,100K (62) 20,000 34 (85%) 2,300 86.8% (69.7%)
Sylvania Cool White F25T12/CW 4,200K (62) 12,000 25 (62.5%) 1,860 70.2% (56.4%)
Philips Deluxe Cool White F34/CWX/RS/EW 4,200K (89) 20,000 34 (85%) 1,580 59.6% (47.9%)

Full Spectrum Lamps that consume 34 or fewer watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Philips Ultralume F34/50U/RS/
5,000K (85) 20,000 34 (85%) 2,580 100% (79.4%)

Daylight Lamps that consume 34 or fewer watts of electricity (T12 lamp design)
(Requires a T12-40 Watt Rapid Start Ballast)

Philips Daylight Deluxe F34/DX/RS/
6,500K (84) 20,000 34 (85%) 1,775 100% (81.4%)

Warm White Lamps that consume 32 watts of electricity (T8 lamp design)
(Requires a T8-32 Watt Instant Start Ballast, See Note 5)

Philips TL 80 3000K F32T8/TL830 PLUS/ALTO 3,000K (86) 24,000 32 (80%) 2,800 100%
Philips TL 80, 3500K F32T8/TL835 PLUS/ALTO 3,500K (86) 24,000 32 (80%) 2,950 100%
Sylvania Octron 735 F032/735 3,500K (75) 20,000 32 (80%) 2,520 85.4%

Cool White Lamps that consume 32 watts of electricity (T8 lamp design)
(Requires a T8-32 Watt Instant Start Ballast, See Note 5)

Sylvania Octron 841 F032/841/ECO 4,100K (82) 20,000 32 (80%) 2,950 100%
Philips TL 741 4100K F32T8/TL741 ALTO 4,100K (86) 30,000 32 (80%) 2,850 96.6%
Philips TL 80 4100K F32T8/TL841 PLUS/ALTO 4,100K (86) 24,000 32 (80%) 2,800 94.9%
Sylvania Octron 741 F032/741 4,100K (70) 20,000 32 (80%) 2,800 94.9%
The information in this table was researched from January to March, 2002. Manufacturers may discontinue or replace products at any time, or make improvements to existing products that change their specifications. Check the manufacturers own specifications for the latest information. The author is not affiliated with any of the manufacturers listed and is not employed by the lighting industry.


[1] Color temperature is measured in Kelvin's and is a more precise indication of the color of the light produced than a lamp model name may convey. A lower number is a more-red color while a higher value is a more-blue or violet color.

[2] The power consumption and light output shown assumes that 40 or 34 watt bulbs are used with 40 watt ballasts, 32 watt lamps with 32 watt ballasts, and that there are no power-saving ballasts or other devices present. Such extra devices will reduce the light levels produced and may also alter the color temperature. 34 watt bulbs are generally required to be used with 40 watt ballasts and these lamps cannot be used in conjunction with 34 watt ballasts or other power-saving devices.

[3] Lumens ratings generally represent light output after the first 10 to 20 hours of initial operation. Light output usually declines slowly until the bulb reaches the end of its serviceable life. When provided by the lamp maker, the "Design Lumens" value is shown.

[4] The value shown is the percentage of light produced by a given lamp when compared to the brightest lamp of the same class (same watts and light temperature). On the "energy saver" lamps, the value in parentheses shows the percentage of light produced when compared to the best traditional 40 watt lamp of the same color temperature. Although lower power lamps invariably produce less light than the brightest 40 watt lamps, knowing the difference can be significant. For example, a 34 watt lamp uses 85% of the power consumed by a 40 watt lamp, but if a given lamp only produces 55% of the light that the best 40 watt lamp produces, that 34 watt lamp probably isn't a very good one.

[5] This next generation lamp design uses a T8 bulb (1" diameter), and requires a ballast specifically designed for these instant start lamps. 32 watt lamps are not interchangeable with the 40 and 34 watt lamps.

[6] Values that appear in bold were significantly higher or lower than the other lamps in that category. For example, if most lamps in a category had a life expectancy of 20,000 hours, a lamp with a 12,000 hour life expectancy would appear in bold. Lamps with unusually low light output or longer life expectancies also appear in bold.

As demonstrated in the table above, phrases like "Super Saver" and "Energy Saver" typically mean that the lamp consumes less than the traditional 40 watts, but also produces far less light, and in a few cases, such lamps have significantly shorter operating life. One of the most curious items found in researching this table was that the Sylvania lamps that include the word "Deluxe" produce far less light than almost all other models including other lamps from Sylvania, making the use of "deluxe" somewhat misleading.

When buying fluorescent lamps at "home improvement" stores, frequently the least efficient lamps are the ones most prominently displayed. The lamps placed next to "shop fixtures" tend to have the lower light output, and less desirable light quality. Usually, these are also the least expensive lamps, while those that produce more light or better quality light might cost up to 50% more than those other lamps. However, for the higher light quantity and quality, the best lamps may be worth it to you.

The tables above have a lot of information, but it really comes down to this: Most lamp packaging provides at least some of the information shown above, which will let you do on-the-spot comparisons. This small table provides a general rule of thumb for getting the best brightness value from the four lamp color categories for 48" 40 watt lamps:

Lamp Color Color Temperature Watts Minimum Acceptable Lumens Best Available Lumens
Warm White 3,000K to 3,500K 40 2,880 3,300
Cool White 4,100K to 4,200K 40 2,880 3,300
Full Spectrum 4,800K to 5,500K 40 2,950 3,250
Daylight 6,000K to 7,000K 40 2,000 2,180

Some lamps have color temperatures just beyond the ranges shown. For example, some compact fluorescent lamps have a color temperature of 2700K and call themselves "Warm Color" rather than "Warm White". These tend to have a red to pink tint rather than the more orange to yellow tint of typical Warm White lamps.

T8 Versus T12: New Fixtures and Conversions

A lot of fluorescent lamp, fixture and ballast makers are really marketing the 48" T8 lamp systems as the preferred new installation lighting system over the existing T12 48" lamp systems. They are also marketing conversion packages to re-work existing T12 fixtures with T8 lamps and ballasts.

As demonstrated above, even the best T8 48" lamps still produce less light than the best T12 48" lamps, but the T8 lamps also use less power. If you are looking at this simply from the point of view of which system will give me the most light for the amount of electricity consumed without considering cost, use this formula:

Lumens divided by Watts = Lumens per Watt
3,300 / 40 = 82.5 Lumens per watt (for best T12 40 watt fluorescent lamp)
2,650 / 34 = 77.9 Lumens per watt (for best T12 34 watt fluorescent lamp)
2,950 / 32 = 92.19 Lumens per watt (for best T8 32 watt fluorescent lamp)
Based on that formula alone, the best T8 lamps available produce about 10% more light for the power consumed, as compared to the best T12 40 watt lamps available. However, converting existing systems may not be cost effective in the short term, and the lower total light output that will occur if replacing 40 watt lamps may be a problem.

If you are building a facility from scratch (or installing new fixtures) AND are willing to buy the T8 system (which will be more expensive, both in lamps and in fixture cost), the savings will eventually be recovered, but it will take several years. The price of the fixture and parts will dictate when T8 will be cheaper than T12. (If your landlord has to install the fixtures and lamps anyway in space you are leasing, and then you pay the monthly electric bill, get the landlord to install T8.)

If you are in an existing facility and are considering replacing existing existing "energy saving" 34 watt T12 lamps and ballasts with T8 lamps and ballasts, the result will be a small power savings (2 watts per lamp), and a 15% light output increase. However, the cost recovery per fixture will take many years.

For example, a T8 ballast (all of which are solid state devices) that is capable of operating one to four lamps will cost about $30 US in single quantities, plus T8 48" lamps, at $4 US each, plus electrician costs to alter the wiring in the fixture. (This is because T12 and T8 fixture wiring is slightly different and must be changed.) The cost to overhaul a four lamp fixture will be in the neighborhood of $46, not including electrician charges.

The best possible power savings from an existing fixture conversion would be 8 watts per lamp (from 40 watt to 32 watt lamps), or 32 watts per four-lamp fixture. If your local electricity costs $0.08 US per kilowatt hour, the savings in power consumption for 8,760 hours (the lamp burning constantly for a year), would be $22.43 US per year for that fixture. The cost recovery for just the ballast and parts would be about two years if the fixture is illuminated all the time. With a more typical eight-hour per day use of the fixture, it would take six years to recover just the parts cost of the conversion of each fixture, not counting the cost of the electrician needed to rework the fixtures.

If your building maintenance people have already installed T12 34 watt lamps, converting to T8 32 watt lamps would only save eight watts per four-lamp fixture, and it would take over twenty-five years (assuming eight-hour use) to recover the conversion costs, but you will get more light. Recently, T8 25 watt lamps appeared on the market, but their light quality is so poor that I cannot recommend them in replacement configurations.

Another thing to consider is that a fixture containing 40 watt T12 lamps that is converted to 32 watt T8 lamps will be producing a little less light than before, which may require fixtures to be repositioned or additional fixtures may need to be added to compensate. Cases where the brightest T12 lamps were already installed and were replaced with second-best light producing T8 lamps will enlarge the difference in light output between the two systems.

Fixtures with just two or three 40 watt T12 lamps that are converted to T8 systems are the ones most likely to reduce lower light levels so much that it becomes objectionable. Existing fixtures contaning T12 34 watt lamps that are converted to T8 32 watt lamps will actually see a light output and quality of light improvement. If T8 25 "energy savers" are used in fixtures that formally had 34 or 40 watt lamps, the new light level will undoubtedly be unacceptable.

T8 Versus T12: Fixture Replacement instead of Conversion

It should also be mentioned that in cases where a fixture containing T12 40 or 34 watt lamps is completely replaced with a modern fixture designed for T8 32 watt lamps, the usable light levels could be the same or improved, as fixture designs have improved and would have newer materials, and so less light is lost in the fixture compared to older equipment.

I personally tried this at home in June of 2007, replacing a fixture that used four T12 40 watt lamps probably made 15 to 20 years ago with a new fixture of the same style made by the same manufacturer. This new fixture used four T8 32 watt lamps. In my case, the lamps being replaced were an average of 3,000 lumens, and the new T8 lamps were 2,850 lumens. Therefore, the new lamps emit about 95% of the light emitted by the old lamps. However, thanks to a less-yellowed/cloudy plastic lens on the new fixture, the usable light of the new fixture and lower-power lamps is noticibly greater than the older fixture. In addition, the old fixture was a rapid start design so now I no longer have that start-up delay when I turn on the light switch for the room.

The only negative I found was the solid-state ballast in the new fixture noticbly interferes with reception of NTSC over-the-air channel 5. Despite that, the results were good enough to justify replacing two similar fixtures elsewhere in the house with T8 designs. I used Cool White lamps, particularly in laundry work areas and closets, because it is difficult to tell the difference between black and dark blue clothing under Warm White lighting. That is a personal preference, as I also prefer white wall paint over antique white.

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