How Many Lights Do I Need For My Parking Lot?
When creating a safe work environment, for customers or employees, one of the first spots you need to consider is your parking lot lighting. When the visitors and the employees come and go, they are at risk of any hazards or safety issues posed by your parking lot. Often, it potentially leaves you open to litigation for accidents that may occur in areas without adequate parking lot lighting. Sometimes, dark spots in the parking areas can encourage a criminal element. As such, the importance of adequate parking lot lighting cannot be overstated. But when you have decided to transform your parking lot with the LED lighting technology, how many lights will you need?
Focus On Footcandles On The Ground And Uniformity.
Footcandles are the most common unit of measurement used by lighting experts to calculate light levels in outdoor spaces and businesses. A foot-candle, by definition, is the illuminance of a one square foot surface from a uniform source of light. It is, therefore, a measure of the amount of light that reaches a surface area. From a candela light source, light falling on one square foot of area equals one lumen per square foot.
One functional determinant for the adequate light level is the activeness of the area. Sometimes .5 fc can be enough in low activity areas, while in high activity areas, five fc is standard. However, it is not uncommon to find parking lots with a low foot-candle level below the recommendation of lighting experts, which essentially means poor visibility and appeal. Lighting experts recommend a minimum light level of 1 fc throughout the desired area and 2 to 4 fc being more desirable for appeal and optimal visibility.
Lighting uniformity (which translates to the human perception of how evenly illumination is distributed throughout the parking lot) is expressed as the ratio of maximum-to-minimum illumination levels (lowest light level reading and average light level of a specific area). Currently, the recommended ratio for most outdoor parking lot applications is 3:1. With the LED technology, there is excellent uniformity generated due to the inherent quality of these lights. Typically, when lighting lacks uniformity, it is a result of space between the fixtures. Often, other landscaping, such as trees, get in the way, which complicates the uniformity.
Pole Height
LED Parking Lot lights are typically pole top lights or pole-mounted shoebox lights between 15 feet and 40 feet high. The choice of the mounting height, pole placement, number of lights, and beam angles determines your parking lot illumination quality. Before designing the lighting for your space, you must determine whether the area where your company is located has maximum height allowances. The information is available to commercial property owners. The location of your business also determines the height of the poles. If you neighbor other property, you might have to consider the height to prevent glare to other individuals beyond your lot.
Mounting heights for parking lot lights can range from 12ft. to 20 ft. but, in some cases, the poles can go as high as 35 ft. The size of the parking lot will determine the recommended height of your poles. For large areas, taller poles are preferred, and vice versa.
15ft: use 2-4 per pole
Typically, a 15 ft. pole is used with a type 3 lighting pattern, or 2-4 light heads per pole. With a 15 ft. light pole and a three-light pattern, the coverage area on the ground will be about 15ft. on each side and 15 ft. forward. The figures are not exact, but they give you a way of estimating your light heights and coverage area using the type 3 light pattern.
Once the mounting height is determined, you can then decide on the spacing of your fixtures. The rule of thumb as far as this is concerned is: the higher the mounting height, the fewer the poles you need. (assuming you get your beam angles correct) The following are different spacing set-ups with a 15-foot pole.
Use 150 watts for standard at 60 ft.
In replacing old 400 watt HID parking lot lights with LED, conversions are made based on the current wattage for your halide lamps. LED Parking lot lights typically utilize wattages between 100 W and 450 W. 150 watt parking lot light LED generates about 20 000 lumens. 60 ft. spacing is a common choice that generates average brightness commonly used in areas without the need for optimal visibility. Lightly used back lots require such a set-up.
Use 150 watts for bright at 40ft spacing.
If you reduce your spacing with a 150 watt light head to about 40 ft., the lighting coverage is better with more brightness. A brighter lighting plan creates more appeal and illumination and eliminates any shadowy areas that could act as black spots. Smaller spacing creates overlap in the lighting and enhances visibility. Small-sized parking lots such as in homes or small retail joints may require such a set-up.
20 ft. use 2 to 4 light fixtures per pole
A 20 ft. pole is ideal for a medium to large-sized parking lot. Each pole can be fixed with 2-4 light fixtures. At 20ft., the light is dispersed further than a 15 ft. pole, making it better for a bigger parking lot. At this height, the following lights and spacing are commonly used.
1. Use 300 watts for standard at 60 ft.
A 300 watt parking lot light fixture generates about 40,000 lumens. At a spacing of 60 feet, with 2-4 light fixtures at 20 ft. high, there is more brightness than a 150 watt light fixture at the same spacing. However, the spacing is still big enough for optimal brightness and visibility needed in a commercial setup. Every spot in the parking lot demands a bright and optimal view, such as a car dealership yard.
2. Use 300 watts for bright at 40 ft. spacing.
In this set-up, the spacing is minimized at the same height and lumens per light fixture. Therefore, the illumination is brighter. There is an enhancement of visibility and appeal of the parking lot. It is ideal for medium-to-large sized parking lots which demand more appeal and brightness, such as a big retail outlet. More light reaches the ground and covers a greater area. Most medium to large-sized parking lots uses this set-up.
3. 25ft--try and use 4 per pole: the most cost-effective
Using four fixtures in a pole is the most effective lighting design. It ensures cross over lighting from multiple directions, which eliminates bright spots and reduces shadowing. At 25 ft., the light poles are pretty high, and only a few of them are needed to light up a large area. Therefore, fewer parking lot lights are used, saving on utility costs.
Use 300 watts for standard at 60 ft., with four each
This is a widely-spaced set-up where a few parking lot lights are used, with tall poles. It is commonly utilized in large commercial parking lots lights and in areas that are scarcely populated. It is a cost-effective choice utilizing only a few poles.
Use 300 watts for bright at 40ft., spacing with 4 each
When the spacing is reduced to 40 feet, with four fixtures on each pole, the illumination is brighter, and visibility is enhanced. It is ideal for large commercial parking lots. Retails and sports courts also require such bright lighting.
Make Sure Your Coverage Is Even
The most typical parking lot light pattern is a type III, which has been the standard for long. While determining the coverage for light is complicated, the coverage must be even to provide uniformity in lighting. Designing the lighting pattern calls for an expert. Be sure to contact us for an expert opinion on your parking lot lighting needs.
Consider Motion Sensors
A good way to reduce energy and improve security is to go with motion sensors. Microwave based motion sensor parking lot lights now reach far enough to be used at up 30' poles. Best used at under 22 for larger distance away.
