UFC 3-530-01
22 August 2006
sources. (Figure 2-7 can also be used to interpolate multipliers.) The
values obtained are listed in the Effectiveness Multiplier row.
Step #3: Calculate Illuminance: AGI calculated the illuminance shown in
the next line of the comparison. This value is based on the initial lamp
lumens for each source as published by the lamp manufacturer. However,
because different light sources provide varying levels of visibility at night,
effective values are a better metric for comparison.
Step #4: Determine the effective illuminance: The effective illuminance is
listed in the fourth line for each light source. This is simply the product of
the illuminance and the effectiveness multiplier. As shown in the table,
metal halide provides higher effective illuminance and better effective
uniformity than an HPS system. This is true even though the metal halide
lamp has fewer initial lumens than HPS.
PARKING LOT LIGHTING
AVG
MAX
MIN
AVG/MIN
MAX/MIN
250 Watt Metal Halide (150' spacing)
Step 1: Luminance
0.74
2.1
0.36
2
6
Step 2: Effectiveness Multiplier
1.4
1.3
1.5
Step 3: Illuminance
1.17
2.43
0.5
Step 4: Effective Illuminance
1.64
3.04
0.75
2
4
250 Watt HPS (150' spacing)
Step 1: Luminance
0.81
2.5
0.36
2.3
7.1
Step 2: Effectiveness Multiplier
1
1
1
Step 3: Illuminance
1.28
3.27
0.58
Step 4: Effective Illuminance
1.28
3.27
0.58
2
6
Economic Comparison
The next table summarizes an economic comparison of these two light sources for the
same parking area. The analysis considered the initial cost of the lighting equipment,
the energy costs incurred during the analysis period, and the lamp replacement costs.
(The complete cost analysis for HPS, metal halide, and induction lamps can be seen in
Appendix D.) The table illustrates that the metal halide source is more expensive for
this particular application.
Summary of Total Cost for Analysis Period
Difference for
Total Cost for 20 Year
Average
Analysis
Annual
Analysis
Luminaire
Difference
Period
Quantity
Equipment Energy
Replacement Period
Light Type
,528
High Pressure Sodium
16
,120
,808
,600
,860
Metal Halide
16
,280
,220
,360
-,331
-7
Equipment Cost: Metal halide lamps are slightly more expensive than
HPS lamps, increasing the equipment cost.
7-5
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