22 August 2006
Energy Cost: Even though the lamps are the same wattage, the actual
ballast input wattage for metal halide is lower than HPS. This gives metal
halide a small energy cost savings.
Lamp Replacement Cost: The metal halide lamps (with the recommended
color temperature of 3000K) have a lower life than HPS. This results in a
more frequent replacement of metal halide lamps.
The net additional expense of metal halide may be acceptable if the improved visibility
is required for better reaction time or improved security. This analysis compares an
equal number of poles and luminaires. Metal halide may become the more cost
effective choice as applications increase in size. Because metal halide provides
improved illuminance and uniformity, spacing may be increased over a comparable
HPS design. If a row of equipment can be reduced with the increased spacing, metal
halide will provide savings in all of the cost categories shown in the table.