| Online Lighting Calculator |
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TBC = to be calculated
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Factor |
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Initial lamp output (lumens) |
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Design (40% of life) lamp output (lumens) |
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Lamp life (hours) |
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Fixture quantity |
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Fixture input power (watts) |
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Total kilowatts |
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Fixture efficiency (%) |
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Design lumens from fixture(s) (lumens) |
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Conversion factor, standard lumens to pupil (lumens)a |
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Net design pupil lumens from fixture(s) (lumens) |
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Annual operating hours |
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Annual electricity consumption (kilowatt-hours per year) |
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Annual savings (kilowatt-hours per year) |
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Electricity cost per kilowatt-hour ($) |
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Annual kilowatt-hours cost ($) |
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Annual savings ($) |
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Cost of retrofit ($) |
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Simple payback period (years) |
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NA = not applicable |
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Notes:
a. Use data from Table 2 for the appropriate conversion factor. Use values of 1.0 to do the calculation without considering pupil lumens |
Table 2: Conversion factors for lumens to pupil lumensCorrection factors applied to conventional values of lumens per watt yield a value for pupil lumens per watt, which is a measure of how effectively the eye sees the light that is emitted. The pupil is more receptive to light at the blue end of the spectrum. |
| Light source |
Conventional lumens per watt
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| Low-pressure sodium |
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| 5,000-K T5 fluorescent |
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| 4,100-K T8 fluorescent |
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| Clear metal halide |
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| 5,000-K pure triphosphor fluorescent |
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| 3,500-K triphosphor fluorescent |
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| 50-watt high-pressure sodium |
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| 2,900-K warm white fluorescent |
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| Daylight fluorescent |
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| 35-watt high-pressure sodium |
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| 5,000-I 90 CRI fluorescent |
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| Vitalite fluorescent |
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| Deluxe mercury vapor |
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| Standard incandescent |
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| Tungsten halogen |
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Notes: K = Kelvin; CRI = color rendering index. |