How to Choose The Power Value for Outdoor LED Parking Lot Lights?


When we discuss parking lot lighting, we are making reference to the pole-mounted lights frequently seen in parking lots. These outdoor lighting fixtures, if converted to LED can provide excellent benefits to both building owners and facility managers alike.

Outdoor LED Parking lot lights are important for vehicular and especially pedestrian safety, for protection against assault, theft, and vandalism, for the convenience of the user,  and in some cases for business attraction. Important lighting design criteria for parking areas are source/task/eye geometry, shadows, direct and reflected glare, peripheral detection, modeling of faces and objects, light pollution and trespass, and vertical illuminance.

So how to decide the power of led parking lot lights? Let’s show you as below step by step.


Energy Efficiency Metrics

A primary motivator for any business owner is cost & energy savings. There are different energy efficiency metrics for outdoor led parking lot lights. Although there are several metrics to describe energy effi­ciency, here we consider three lighting-specific metrics: efficiency (very simple), efficacy (simple), and lighting power density (complex). This guide primarily focuses on efficacy and demonstrates how efficacy incorporated with other elements can reduce power densities.

Efficiency (LE)

Efficiency is a measure of how effectively a device converts the input into the output. Luminaire efficiency (LE) is the light leaving the luminaire divided by the light generated by the bare lamp (light bulb) when operated outside of the luminaire. Because both values (the light leaving the luminaire and the light generated by the light source[s]) have the same unit, luminaire efficiency is, therefore, a unitless ratio.

Different luminaires will have different efficiency values. This is up to the light loss of the fixture. As for led parking lot street light, the luminaire efficiency can get above 95% because it is the only from the loss of optical lens. 


Efficacy (LPW)

Efficacy is the capacity to produce an effect. In lighting, efficacy is measured in lumens per watt (lm/W, also abbreviated LPW). Efficacy can apply to light sources or luminaires. The greater the efficacy, the more light is generated for the same watts. Most people are familiar with this metric related to vehicles; for example, a car that gets 30 miles per gallon is more efficacious than a car that gets 25 miles per gallon.

Lightide’s outdoor led parking lot lights can get 130~150 lumens per watt because of the excellent chip used. So 120W-150W LED can replace 400W metal halide lamps. 


Lighting Power Density (LPD)

Lighting power density (LPD) is the total input power (i.e., including the driver or ballast) multiplied by the total number of luminaires divided by the area in which the equipment is installed. Many energy codes use this metric; however, it does not actually focus on energy. Energy is power multiplied by time, so it is important to distinguish between power (watts) and energy (watt-hours). Lighting power density calculations do not indicate any energy savings as a result of the use of lighting controls.

Illuminance recommendations for active lots open to the public, customers, or employees. The illuminance should be measured, or calculated, on clear pavement, without any parked vehicles. The maximum and minimum values are maintained illuminances. This condition occurs just prior to lamp replacement and luminaire cleaning.


LED Parking Lot Lighting System Performance  

A. Lighting Zone

To provide as much information about the area lighting zone, both the ASHRAE/IESNA Std. 90.1 and IES RP-33 exterior lighting zone definitions are combined below for zones where area lighting is expected to be applied. Lighting Zone-0 (LZ0) is not expected to include area lighting as described in this specification but is described here for reference.

1. Lighting Zone-2 (LZ2) 

Areas predominantly consisting of residential zoning, neighborhood business districts, light industrial with limited nighttime use, and residential mixed-use areas. Lighting may typically be used for safety and convenience but it is not necessarily uniform or continuous. After curfew, lighting may be extinguished or reduced as activity levels decline.

2. Lighting Zone-3 (LZ3)

Areas not classifiable under the other four Lighting Zones. Areas of human activity where the vision of human residents and users is adapted to moderately high light levels. Lighting is generally desired for safety, security, and/or the convenience and it is often uniform and/or continuous. After curfew, lighting may be extinguished or reduced in most areas as activity levels decline.

3. Lighting Zone-4 (LZ4) 

High activity commercial districts in major metropolitan areas as designated by the local jurisdiction. Areas of human activity where the vision of human residents and users is adapted to high light levels. Lighting is generally considered necessary for safety, security, and/or the convenience and it is mostly uniform and/or continuous. After curfew, lighting may be extinguished or reduced in some areas as activity levels decline.

Lighting Zone Description
Zone 1 Developed areas of national parks, state parks, forest land, and rural areas
Zone 2 Areas predominantly consisting of residential zoning, neighborhood business districts, light industrial with limited nighttime use and residential mixed-use areas
Zone 3 All other areas not classified as lighting zone 1, 2 or 4
Zone 4 High-activity commercial districts in major metropolitan areas as designated by the local land use planning authority


B. Exterior LED Parking Lot Lights Power Choice

1. Energy Conservation

Outdoor LED Parking Lot lighting must meet the following lighting power density (LPD) requirements (paved area of site defines the applicable area) based on the exterior zone location for the project.
a. Lighting zone (LZ-2) – LPD maximum of 0.05 W/SF
b. LZ-3 – LPD maximum of 0.06 W/SF
c. LZ-4 – LPD maximum of 0.08 W/SF

2. Allowances include a base allowance plus tradeable allowance

Outdoor led parking lot lights power limits come in up to three types for most building energy codes. These include watts per square foot, watts per linear foot, and watts per location or application. The exterior power limits are divided into two categories based primarily on the critical nature of the application. The first category includes tradable applications that function like interior LPDs where it is the total watts used across all lighted applications that must not exceed the combined allowance for those applications. The second category includes non-tradable applications that are provided an allowance that can only be used for that application. Any unused watts cannot be applied to other applications. For these non-tradable applications, the allowances are truly used it or lose it.

3. Allowances Sheet
Allowance Location Zone 1 (LZ-1) Zone 2 (LZ-2) Zone 3 (LZ-3) Zone 4 (LZ-4)
Base Site Allowance ————— 350W 400W 500W 900W
 Tradeable Allowance                                                                                            Uncovered Parking Areas
Parking areas and drives 0.03W/ft2 0.05W/ft2 0.06W/ft2 0.08W/ft2
                                                                                                   Building Grounds
Walkways and ramps less than 10 feet wide 0.5W/linear foot 0.5W/linear foot 0.6W/linear foot 0.7W/linear foot
Walkways and ramps10 feet wide or greater Plaza areas, Special Feature Areas 0.10W/ft2 0.10W/ft2 0.11W/ft2 0.14W/ft2
Building facades No allowance 0.075 W/ft2 of gross above-grade wall area 0.113 W/ft2 of gross above-grade wall area 0.15 W/ft2 of gross above-grade wall area
Automated teller machines (ATM) and night depositories 135 W per location plus 45 W per additional ATM per location

Uncoveredentrances and gatehouse inspection stations at guarded facilities 

0.5W/ft2 of area
Uncoveredloading areas for law enforcement, fire, ambulance and other emergency service vehicles 0.35W/ft2 of area
Drive-up window and doors 200 W per drive-through
Parking near 24-hour retail entrances

400 W per main entry

Get A Professional Lighting Assessment 

LED technology is continually and rapidly improving. And the price of commercial outdoor LED parking lot lights continues to drop. If you’re considering a switch to LED lighting, but you’re still unsure whether the cost savings,  justify what could be a substantial investment, schedule a complimentary, no-hassle Quality Lighting Assessment from Lightide. We will perform a complete cost savings analysis and ROI timetable based on an evaluation of your current system.  And projected cost estimates for our recommended lighting solutions.

Lightide Manufactory Co., Ltd.  


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