COMPARING DIFFERENT KINDS OF LAMPS

INSTRUCTIONS

Entering a lamp into a row:

• Enter the values for one kind of lamp and application into any row.
  1. Enter the name of the product in the "PRODUCT NAME (manufacturer/model)" space.
  2. Enter the rated power (not the equivalent-brightness power) in the "RATED POWER (watts)" space.
  3. Enter the rated brightness of the lamp in lumens in the "BRIGHTNESS (lumens)" space.
  4. Enter the rated average life from the package in the "AVERAGE RATED LIFE (hours)" space.
  5. Enter the type of lamp from the table above in the "TYPE (BCDFHILNOS)" space.
  6. Enter the color temperature (In Kelvins) in the "COLOR TEMP (K)" space.
     • If the color temperature is not specified, use the chart above.
  7. Enter the price of one bulb in the "UNIT PRICE ($)" space.
     • For a package deal, divide the group price by the number of bulbs. Include any sales tax.
  8. Enter the avg number of hours the lamp is used each day in the "DUTY CYCLE (hr/day)" space.
  9. Enter the avg number of times the lamp turns on each day in the "DAILY CYCLES (start/day)" space.
  10. Do not enter values under the "RESULTS" heading. This page will calculate those.
  11. At the bottom, enter the charge per kilowatt-hour (KWh) in the "Power cost ($ / KWh)" space.
      • Include any relevant taxes.
  12. Enter the avg number of power dropouts (sags) per year in the "Power dropouts: (sags/year)" space
• You may enter up to 4 lamps at a time.

Comparing different lamps:

• Enter up to four different kinds of lamps, with identical operating conditions.

Comparing different operating conditions:

• Enter the same kind of lamp into each row with different operating conditions.

Comparing artificial light sources to light from the sun:

• Enter an "S" in the "TYPE" space on one line. No other entries are needed in that row.

Starting the calculation:

• Click on the CALC button to start the calculation.

Interpreting the results:

• "EFFICIENCY (Lm/W)" gives the lamp's efficiency of converting electricity into light.
• "DAILY COST ($/day)" gives the dollar cost of operating the lamp.
• "BREAK EVEN (min)" shows how long the lamp is left on to equal the cost of starting the lamp.
  • This includes the cost of replacing the lamp because starting it shortened its life.
• "RELAMP PERIOD (years)" is the expected time between lamp burnouts and replacements.
• "COLOR MATCH (%)" is the percentage of the color rendering and readability of sunlight.

Factors affecting the cost of operating an electric lamp:

• The efficiency of the conversion of electricity into light determines part of the operating cost. More efficient lamps use less electricity to produce the same light.
• The price of the replacement lamp, needed when the lamp burns out, adds to the operating cost of the lamp.
• Anything that shortens the life of a lamp increases the cost of operating it.
• The lives of some types of lamps shorten each time they are turned on.
• The break-even point is the point where the use of electricity exceeds the shortened-life cost of starting the lamp. To save money, leave the lamp on if it will be needed again within the break-even period.
• Costs not included in the table include union-scale labor rates to have the bulb changed, and temperature effects on lamp life.
• Rates often go down after so many Kilowatt-hours (KWh) are used.

Factors affecting the life of a lamp:

• Incandescent lamps:
  • The primary limiting factor for the life of an incandescent lamp is the time it is left burning.
  • The higher the wattage, the shorter the life of the lamp.
  • The size and design of the envelope can affect the lamp life.
  • Operating an incandescent lamp at a voltage higher than the rated voltage sharply reduces its life.
  • Operating an incandescent lamp at too low a voltage extends its life.
  • Operating an incandescent lamp at a temperature higher than room temperature reduces its life.
  • Operating an incandescent lamp at too low a temperature can extend life, but can also cause early failure.
  • Using a lamp of higher wattage than the fixture is rated for shortens the life of both.
  • Starting the lamp shortens its life by about a minute.
  • A power sag can slightly lengthen the life of the lamp.
  • A power surge can cause sudden failure of the lamp, or can shorten its life sharply.
  • A power failure can cause a lamp burnout, or greatly shorten its life.
  • Vibration can shorten the life of an incandescent lamp.
• Halogen lamps:
  • The primary limiting factor for the life of a halogen lamp is the time it is left burning.
  • The higher the wattage, the shorter the life of the lamp.
  • The size and design of the envelope can affect the lamp life.
  • Operating a halogen lamp at a voltage higher than the rated voltage sharply reduces its life.
  • Operating a halogen lamp at too low a voltage also shortens its life.
  • Operating a halogen lamp at a temperature higher than room temperature reduces its life.
  • Operating a halogen lamp at too low a temperature reduces its life.
  • Using a lamp of higher wattage than the fixture is rated for shortens the life of both.
  • Starting the lamp shortens its life by about a minute.
  • A power sag can slightly shorten the life of the lamp.
  • A power surge can cause sudden failure of the lamp, or can shorten its life sharply.
  • A power failure can cause a lamp burnout, or greatly shorten its life.
  • Vibration can shorten the life of a halogen lamp.
• Fluorescent, gas-discharge, and metal-vapor lamps:
  • The primary limiting factor for the life of a gas-discharge lamp is the number of times the lamp is started.
  • This kind of lamp usually lasts an average of about 6500 starts.
  • Operating this kind of lamp at a voltage higher than the rated voltage sharply reduces its life.
  • Operating this kind of lamp at a voltage lower than the rated voltage sharply reduces its life.
  • Operating this kind of lamp at a temperature higher than room temperature might reduce its life.
  • Operating this kind of lamp at a temperature lower than the rated temperature sharply reduces its life.
  • Installing the wrong lamp type can cause quick failure, and can destroy the ballast. It can also cause failure to start.
  • Installing the lamp wrong can destroy it.
  • Starting the lamp shortens its life by one start.
  • A power sag shortens the lamp life by one start.
  • A power surge can cause sudden failure of the lamp, or can shorten its life sharply.
  • A power failure can cause a lamp burnout, or can shorten its life by one start.
  • Vibration can shorten the life of this kind of lamp.
• Light-emitting diodes (LEDs) and electroluminescent lamps:
  • The primary limiting factor for the life of a semiconductor lamp is catastrophic failure.
  • This kind of lamp usually lasts until something breaks it.
  • Operating this kind of lamp at a voltage higher than the rated voltage can cause sudden failure.
  • Operating this kind of lamp at a voltage lower than the rated voltage can keep the lamp from turning on.
  • Operating this kind of lamp at a temperature higher than room temperature might cause a sudden failure.
  • Operating this kind of lamp at a temperature lower than the room temperature has no effect.
  • Installing the wrong lamp type can cause quick failure, and can destroy the ballast. It can also cause failure to start.
  • Installing the lamp wrong can destroy it.
  • Starting the lamp has no effect on its life.
  • A power sag has no effect on the lamp life.
  • A power surge can cause sudden failure of the lamp. This is the usual cause.
  • A power failure can cause a lamp burnout.
  • Vibration can shorten the life of this kind of lamp.

Typical values:

• 60 W light bulb (standard bulb):
  • 60 W, 870 Lumens, 1000 hours, 2700 K, $0.19
• 60 W equivalent compact fluorescent:
  • 13 W, 800 Lumens, 6000 hours, 6000 K, $2.49
• 60 W equivalent LED:
  • 2 W, 750 Lumens, 10000 hours, 6500 K, $100.00
• Typical power company charge:
  • $0.080 / KWh