Lamp color temperature is rated in Kelvin degrees, and the term is used to describe the “whiteness” of the lamp light. In incandescent lamps, color temperature is related to the physical temperature of the filament.

In fluorescent lamps where no hot filament is involved, color temperature is related to the light as though the fluorescent discharge is operating at a given color temperature. The lower the Kelvin degrees, the “warmer” the color tone. Conversely, the higher the Kelvin degrees, the “cooler” the color tone.

Incandescent lamps provide pleasant color tones, bringing out the warm red flesh tones similar to those of natural light. This is particularly true for the “soft” and “natural” white lamps.

Tungsten filament halogen lamps have a gas filling and an inner coating that reflects heat. This keeps the filament hot with less electricity. Their light output is “whiter.” They are more expensive than the standard incandescent lamp.

Fluorescent lamps are available in a wide range of “coolness” to “warmth.” Warm fluorescent lamps bring out the red tones. Cool fluorescent lamps tend to give a person’s skin a pale appearance.

Fluorescent lamps might be marked daylight D (very cool), cool white CW (cool), white W (moderate), warm white WW (warm). These categories break down further into a deluxe X series (i.e., deluxe warm white—deluxe cool white), specification SP series, and specification deluxe SPX series.

Typical color temperature ratings for lamps are 2800K (incandescent), 3000K (halogen), 4100K (cool white fluorescent), and 5000K (fluorescent that simulates daylight). Note that a halogen lamp
is “whiter” than a typical incandescent lamp.Catalogs from lamp manufacturers provide detailed information about lamp characteristics.

Fluorescent lamps and ballasts are a moving target. In recent years, there have been dramatic improvements in both lamps and electronic ballast efficiency.

First, the now-antiquated T12 fluorescent lamps (40 watts) were replaced by energy-saving T8 fluorescent lamps. These original T8 lamps are becoming a thing of the past. The latest T8 high efficiency, energy saving (25 watts vs. 32 watts) lamps have an expected 50% longer life than the original T8 lamps.

The newer T8 lamps use approximately 40% less energy than the older T12 lamps. At $0.06 per kWh, one manufacturer claims a savings of $27.00 per lamp over the life (30,000 hours) of the lamp. At $0.10 cents per kWh, the savings is said to be $45.00 per lamp over the life of the lamp. Using the newer T8 lamps on new installations and as replacements for existing installations makes the payback time pretty attractive.

One electronic ballast can operate up to four lamps, whereas the older style magnetic ballast could operate only two lamps. For a three- or four-lamp luminaire, one ballast instead of two results in quite a saving. Some electronic ballasts can operate six lamps.

Hard to believe! You now can have reduced power consumption and increased light output using electronic ballasts. Today’s high-efficiency ballasts are available with efficiencies of from 98% to 99%.

The only way you can stay on top of these rapid improvements is to check out the Web sites of the various lamp and ballast manufacturers. Today’s magnetic and electronic ballasts handle most of the fluorescent lamp types sold, including standard and energy-saving preheat, rapid start, slimline, high output, and very high output. Again, check the label on the ballast.


The market for magnetic (core and coil) ballasts is shrinking! The National Appliance Energy Conservation Amendment of 1988, Public Law 100-357 prohibited manufacturers from producing ballasts having a power factor of less than 90%.

Ballasts that meet or exceed the federal standards for energy savings are marked with a letter “E” in a circle. Dimming ballasts and ballasts designed specifically for residential use were exempted.

Today’s electronic ballasts are much lighter in weight and considerably more energy efficient than older style magnetic ballasts (core and coil). Energy saving ballasts might cost more initially, but the payback is in the energy consumption saving over time.

Old-style fluorescent ballasts get very warm and might consume 14 to 16 watts, whereas an electronic ballast might consume 8 to 10 watts. Combined with energy-saving fluorescent lamps that use 32 or 34 watts instead of 40 watts, energy savings are considerable. You are buying light, not heat.

When installing fluorescent luminaires, check the label on the ballast that shows the actual volt amperes that the ballast and lamp will draw in combination. Do not attempt to use lamp wattage only when making load calculations because this could lead to an overloaded branch circuit.

For example, a high-efficiency ballast might draw a total of 42 volt-amperes, whereas an old-style magnetic ballast might draw 102 voltamperes.

The higher the power factor rating of a ballast, the more energy efficient. Look for a power factor rating in the mid to high 90s.

Various line currents, volt-amperes, wattages, and overall power factor for various single-lamp
fluorescent ballasts.

Ballast Line Current Line Voltage Line Volt-Amperes Lamp Wattage Line Power Factor
No. 1   0.35                120                              42                    40                    0.95(95%)
No. 2   0.45                120                              54                    40                    0.74(74%)
No. 3   0.55                120                              66                    40                    0.61(61%)
No. 4   0.85                120                              102                  40                    0.39(39%)
No. 5   0.22                120/277                       26                    30                    0.99(99%)