International Dark-Sky Association (IDA)

3545 N. Stewart Ave., Tucson AZ 85716 U.S.A.

E-mail: crawford@darksky.org

WWW: http://www.darksky.org

Operating Data and the Economics of Different Lamps

Information Sheet 4, January 1990

Assume:

4100 hours of use per year (average nighttime hours, dusk to dawn)
8¢ as the cost per KWH (Kilowatt hour, the power rate)

Low Pressure Sodium

 180W 135W 90W 55W 35W 18W
 -----------------------------------------------
Initial Lumens 33000 22500 13500 8000 4800 1800 
Mean Lumens 33000 22500 13500 8000 4800 1800
Lamp Wattage 180 135 90 55 35 18
Circuit Wattage 220 180 125 80 60 30
Intial Lum/watt 150 125 108 100 80 60
Mean Lum/watt 150 125 108 100 80 60
Annual KWH Use 902 738 513 328 246 123
Annual Oper Cost 72ドル.16 59ドル.04 41ドル.00 26ドル.24 19ドル.68 9ドル.84

High Pressure Sodium

 400W 250W 200W 150W 100W 70W 50W
 ------------------------------------------------------
Initial Lumens 50000 27500 22000 16000 9500 6000 4000
Mean Lumens 45000 24750 19800 14400 8550 5500 3600
Lamp Wattage 400 250 200 150 100 70 50
Circuit Wattage 465 294 246 193 130 100 66
Intial Lum/watt 108 94 89 83 73 60 61
Mean Lum/watt 97 84 80 75 66 55 55
Annual KWH Use 1907 1205 1009 791 533 410 271
Annual Oper Cost 152ドル.52 96ドル.43 80ドル.69 63ドル.30 42ドル.64 32ドル.80 21ドル.65

Mercury Vapor

 1000W 700W 400W 250W 175W 100W
 ----------------------------------------------
Initial Lumens 55000 36400 20500 11850 7850 4100 
Mean Lumens 46200 29850 18570 10540 7140 3230
Lamp Wattage 1000 700 400 250 175 100
Circuit Wattage 1090 765 455 285 205 135
Intial Lum/watt 50 48 45 42 38 30
Mean Lum/watt 42 39 41 37 35 24
Annual KWH Use 4469 3137 1866 1169 841 554
Annual Oper Cost 357ドル.52 250ドル.92 149ドル.24 93ドル.48 67ドル.24 44ドル.28

Metal Halide

 Incandescent
 1000W 400W 250W 175W | 300W 200W 150W
 -------------------------------|----------------------
Initial Lumens 110000 34000 19500 14000 | 6360 4000 2880
Mean Lumens 88000 25600 17000 10800 | 6360 4000 2880
Lamp Wattage 1000 400 250 175 | 300 200 150
Circuit Wattage 1140 465 295 220 | 300 200 150
Intial Lum/watt 96 73 66 64 | 21 20 19
Mean Lum/watt 77 55 58 49 | 21 20 19
Annual KWH Use 4674 1907 1210 902 | 1230 820 615
Annual Oper Cost 373ドル.92 152ドル.52 96ドル.76 72ドル.16 |98ドル.40 65ドル.60 49ドル.20

Most columns are lined up at nearly equal lumen output, to show the relative energy & cost savings.

This material is copyrighted (©) by the IDA, or others as noted. It may be reproduced for non-commercial usage provided that credit is given to IDA. Provided here by NELPAG via permission by IDA, to aid in the availability of this important information.

A key source for information on outdoor night lighting is the International Dark-Sky Association (IDA).