Lighting : Safety and Security : Sustainability :

How do LED and Metal Halide Fixtures compare once installed?*

Energy efficiency is an important consideration in the parking structure management.

During the construction of a new facility in 2009, TimHaahs compared the lighting quality of an actual installation of LED and metal halide lighting. The lighting manufacturer commissioned a point-by-point lighting analysis to determine the number of LED fixtures required to replace the 175-watt metal halide fixtures. The lighting engineer for the LED fixtures determined that each metal halide fixture could be replaced by 1.5 50-watt LED fixtures. The photo below illustrates the results.



The LED fixtures appear in the foreground and the metal halide fixtures in the background. The team noted a spotty “checkerboard” pattern on the floor from the LEDs and the lack of illumination on the side walls. Compare the foreground lighting to the metal halide fixtures in the background; the metal halide fixtures have significant lateral and up-light throw, illuminating the walls and the ceiling. We found, in this case, that the metal halide fixtures resulted in the feeling of a more open and uniformly lit space.

While these two lighting configurations were comparable on paper, the reality was significantly different than the analysis. LED illumination at the floor surface was 8 footcandles directly under the fixtures while the metal halide fixtures illuminated to a level of 18 footcandles at floor level at the midpoint between two fixtures.