Formerly dominated by high-pressure sodium (HPS), metal halide (MH), fluorescents and induction lamps, parking garage lighting is now a common application for LEDs. Their benefits often include energy efficiency and whiter light. On the other hand, LEDs have been known to have glare and poor light distribution.
When evaluating LEDs for your garage, consider the following factors.
Safety and Security
Key requirements for parking garages include safety and security. An effective parking garage lighting fixture should provide excellent uplighting to eliminate “cave effect.” Fixtures should have good sidelighting to illuminate columns and signage. Standards specify no more than a 10:1 variance in lighting from a max/min ratio. In other words, no garage section can have more than 10 times the minimum lighting level of any other point in a garage. The garage also should have a 5.0 footcandle minimum lighting level for proper illuminance.
Traditionally mounted at just 8 feet high, parking garage lighting is particularly challenging for directional lighting like LEDs. The glare of many early LED fixtures was dangerous, distracting and a huge potential legal liability if a mishap occurred due to temporary impairment of a person’s vision. LED suppliers have responded with low or no glare designs. Fixtures with double refraction/reflection spread their light effectively and have revolutionized parking lighting. It is also critical to specify that LEDs be shielded with more than a directional TIR (total internal reflection) optic. Virtually all manufacturers of LED parking lighting have shielded options. You must insist on them.
In terms of efficiency, you should not consider an LED fixture that doesn’t have an effective output of at least 100 lumens per watt. Also, you should consider fixture-mounted motion and photocell sensors. Coupled with this technology are and parking guidance systems that can help guide customers quickly to empty spaces.
The structure of a parking garage affects lighting. If your garage is constructed of precast concrete double tees, be sure that lights are installed properly for effective distribution. This structure can be identified in the field by its many deep, upright tees in the ceiling. Fixtures should not be mounted up in the tee because they tend to overilluminate one tee and underilluminate others. Instead, fixtures should be dropped below or nearly below the tee. Garages built of cast-in-place concrete typically have flat ceilings that allow fixtures to be mounted directly to them. For both types, concrete that is light colored or painted in a light color improves light distribution.
With any LED proposal, test the aesthetics. Arrange for your contractor to install a series of at least four units so you can test the lighting in between fixtures. If you don’t like them, try others. Also, insist on certification. Design Lights Consortium (DLC) is the LED standard for lighting. Utilities won’t give rebates unless the fixture selected is DLC listed. You can view the list of certified, high-quality lamps at www.designlights.org.
Do the Math on Savings
A typical garage includes about 300 lighting fixtures. A high percentage of existing garages use 150-watt HPS (with characteristic yellow light) or a 175-watt MH (white light). Let’s consider the economics of the very popular 175-watt MH.
A 175-watt MH consumes about 208 watts (including ballast).
300 fixtures x 208 watts = 62,400 watts or 62.4 kW.
A new LED fixture can replace the 175-watt MH and draw only 45 watts.
300 fixtures x 45 watts = 13,500 watts or 13.5 kW.
The savings in total kW usage is 62.4 kW – 13.5 kW = 48.9 kW.
Most parking garage lighting fixtures operate 24 hours per day. Assume a national average of utility costs to be $.11/kWh.
Annual energy savings by going to the LED:
48.9 kW x 8,760 hours per year (24/7/365) x $.11/kWh = $47,120.
Assume annual maintenance savings by using the new LED over the MH to equate to about 1/4 of the energy savings:
$47,120 energy savings + ($47,120 x .25) maintenance savings = $58,900 total savings!
A typical installed replacement cost using new low or no glare fixtures is approximately $475 per fixture. Assume a national average of a $100 utility rebate per fixture results in the total installed fixture cost to be only $375.
Installed price of $375 x 300 fixtures = $112,500.
The simple payback = $112,500/$58,900 = 1.91 years.
LEDs can be very attractive on energy savings, but insist on glare-free fixtures, test them in place, and by all means don’t delay. Even for garages using T8 fluorescents, great solutions are available to reduce lamp wattage from 32 watts to 18 watts with or without leaving the existing ballast in place.
I want to thank Jeff Pinyot for his contribution to this article. Jeff is Founder and President of ECO Lighting Solutions and ECO Parking Lights. He can be reached at firstname.lastname@example.org or 317-501-2892.
Eric A. Woodroof, Ph.D., is the Chairman of the Board for the Certified Carbon Reduction Manager (CRM) program and he has been a board member of the Certified Energy Manager (CEM) Program since 1999. His clients include government agencies, airports, utilities, cities, universities and foreign governments. Private clients include IBM, Pepsi, GM, Verizon, Hertz, Visteon, JP Morgan-Chase, and Lockheed Martin. In August 2014, he was named to the Association of Energy Engineers (AEE) Energy Managers Hall of Fame.