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LIGHT MEASUREMENT FOR SOLAR STREET LIGHTING SYSTEMS
Solar street lights have three important brightness metrics: candela, lux, and lumens.
- Lumens represent the amount of light output.
- Lux represents the luminous flux per unit area.
- Candela represents the luminous intensity in a specific direction.
Methods for Measuring Brightness, Luminous Intensity, and Illuminance
Lumens: Lumen values are measured using an integrating sphere. The lumen value of a luminaire is typically labeled on the product packaging, allowing buyers to directly assess the brightness of the luminaire based on the lumen value.
Lux: Lux is measured using a lux meter.
Candela: For simple measurements, a portable photometer can be used. However, for engineering projects, a large professional radiometer is required to generate a complete report.
Here is a table summarizing the key points:
Metric | Definition | Measurement Method |
---|---|---|
Lumens | Total amount of light emitted | Integrating sphere |
Lux | Luminous flux per unit area | Lux meter |
Candela | Luminous intensity in a specific direction | Photometer (simple measurements) or radiometer (engineering projects) |
Solar street lights lux level standard. What lux level do I need?
Light measurement for solar street lighting systems
There are two important indicators of the brightness of the solar street light, Lux and Lumens.
Lux and lumens are both units of measurement for brightness. They are used to tell us the amount of illumination output and the brightness of the light falling on a given surface.
Lumens equals light output.
Lux (represented as lx) stands for luminous flux per unit area.
Relationship between lumens and lux:One lux is equal to one lumen per square meter (lm/m2).
In this post, we will explore the Lux standards of street lights and why they are important. If you want to learn about lumens you can check out this article:UNDERSTANDING WATTS AND LUMENS: HOW TO CHOOSE THE RIGHT BRIGHTNESS LIGHT FIXTURE FOR YOUR PROJECT
What is lux in lighting and why is it important?
Lux is a measurement of the light flux falling on a surface. Lux is the international unit of photometry, a method for measuring light intensity. Lux is used to specify the brightness of light or illumination. It is a standard light measurement for all types of lighting, such as household lights, office lights, car headlights, or street lights.
Why Lux Level Make Sense than Lumen
Lumens measure the light output of a single light source. The calculation method for lumens measurement is to multiply the wattage of the light source by the rated lumens per watt of the light source.
Lux is the amount of light on a surface. This can be measured he brightness of light after it travels a certain distance.
In addition to luminance, Lux levels are the best way to measure the brightness of solar street lights. Illuminance measurement can be easily done with just an illuminance meter, while luminance measurement requires specialized equipment and is more difficult to implement.
Now, when you have a solar street light bulb that produces 1000 lumens, its brightness will be different if placed 10 meters away. Therefore, changing the position of the bulb will change the brightness under different Lux levels. Lumens measure the amount of light produced by the bulb; Lux measures the distance light propagates.
Different road solar street lighting Lux levels
What lux level do I need?
According to standards specified in some countries’ government documents, we provide the following recommendations as a reference:
Highway lighting Lux levels
First-class highways, second-class highways: minimum average illuminance maintenance value 20 lx (low standard) / 30 lx (high standard), uniformity minimum value of 0.4;
Third-class highways: minimum average illuminance maintenance value 15 lx (low standard) / 20 lx (high standard), uniformity of 0.4;
Fourth-class roads: average illuminance 10 lx (low standard) / 15 lx (high standard), uniformity of 0.3;
The above illuminance requirements apply only to asphalt roads, and the illuminance requirements for concrete roads can be correspondingly reduced, with a reduction of not more than 30%.
Highway lighting levels should be determined based on the lighting standards of urban roads connected to them, the highway traffic control system, and road partitioning facilities.
The above average illuminance has two standard values, high standard values should be used for the following cases:
- Connected to urban roads with high-grade lighting standards;
- Poor visibility conditions;
- Inadequate highway traffic control systems and road partitioning facilities.
When connected to urban roads with low-grade lighting standards, good visibility, and adequate highway traffic control systems and road partitioning facilities, low-grade values should be used for highway lighting.
Urban road lighting Lux levels
Express roads and main roads: minimum average illuminance maintenance value 20 lx (low standard) / 30 lx (high standard), uniformity minimum value of 0.4;
Secondary roads: minimum average illuminance maintenance value 15 lx (low standard) / 20 lx (high standard), uniformity of 0.4;
Side roads: average illuminance 10 lx (low standard) / 15 lx (high standard), uniformity of 0.3;
The above illuminance requirements apply only to asphalt roads, and the illuminance requirements for concrete roads can be correspondingly reduced, with a reduction of not more than 30%;
City road lighting illuminance values should be determined based on the area where the project is located, road positioning, traffic flow, road partitioning facilities, environmental brightness conditions, and actual needs.
High standard values should be used for the following conditions:
- Central cities and areas, or main roads leading to large public buildings and places in the city;
- Central business districts or main arteries of the city;
- Roads with higher environmental brightness;
- Main roads for people entering and exiting areas such as schools, hospitals, and nursing homes;
- Roads with inadequate road partitioning facilities, mixed traffic of motor vehicles, non-motor vehicles, and pedestrians.
Low standard values are recommended for the following conditions:
- Roads near residential areas and recreational areas;
- Areas with lower environmental brightness.
Rural road lighting Lux levels
Primary roads: minimum average illuminance maintenance value 10 lx (low standard) / 15 lx (high standard), uniformity minimum value of 0.3;
Side streets and lanes: minimum average illuminance maintenance value 5 lx (low standard) / 8 lx (high standard);
Public activity squares: minimum average illuminance maintenance value 10 lx (low standard) / 15 lx (high standard);
The above illuminance requirements apply only to asphalt roads, and the illuminance requirements for concrete roads can be correspondingly reduced, with a reduction of not more than 30%;
Rural road lighting illuminance values should be determined based on the area where the project is located, road positioning, traffic flow, road partitioning facilities, environmental brightness conditions, and actual needs.
High standard values should be used for the following conditions:
- Roads with high traffic flow near towns;
- Large rural roads with dense commercial activities;
- Roads with higher environmental brightness;
- Roads with inadequate road partitioning facilities, mixed traffic of motor vehicles, non-motor vehicles, and pedestrians
Low standard values are recommended for the following conditions:
- Rural roads in remote areas;
- Roads within villages where motor vehicles do not pass through;
- Areas with lower environmental brightness.
Intersection area Lux levels for motor vehicles
- Intersection of Grade 1 with Grade 1, Grade 2, Grade 3: minimum average illuminance maintenance value of 30 lx (low standard) / 50 lx (high standard), uniformity maintenance value of 0.4;
- Intersection of Grade 2 with Grade 2, Grade 3: minimum average illuminance maintenance value of 20 lx (low standard) / 30 lx (high standard), uniformity of 0.4;
- Intersection of Grade 3 with Grade 3: minimum average illuminance maintenance value of 15 lx (low standard) / 20 lx (high standard), uniformity of 0.4;
When the lighting standards at the intersecting roads are both low standard illuminance values, the intersection area should adopt the low standard value, otherwise, the high standard value should be used.
Pedestrian overpass lighting Lux standards
- For pedestrian overpasses with high human flow in rural areas and low human flow in cities: average illuminance of 5lx on the bridge deck, average illuminance of >6lx on the stairway path;
- For pedestrian overpasses with high human flow in cities: average illuminance of 10lx on the bridge deck, average illuminance of >12lx on the stairway path;
- For semi-enclosed pedestrian overpasses: average illuminance of 30lx on the bridge deck, average illuminance of >36lx on the stairway path;
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Choosing the Right Color Temperature CCT for Your Solar Street Light Project
Understanding Solar Street Light Color Temperature ( CCT ): Kelvin
Kelvin is commonly used as a measurement of the color temperature of a light source. The principle of color temperature is based on the frequency distribution characteristics of light emitted by a blackbody radiator at its temperature. Blackbody temperatures below around 4000K appear reddish, while those above 4000K appear bluish, with 7500K appearing blue.
Generally, the Kelvin temperature of a lamp will fall between 2000K and 6500K.
Kelvin temperatures below 3000 produce warm, calm, and inviting light, suitable for general indoor lighting in homes and businesses. Pros: Shorter wavelength yellow light has strong penetration on rainy days. Cons: Low visibility.
LED lights in the 3000K-4500K range are called neutral light. These bright and vibrant lights are very suitable for workplaces such as basements, factories, and hospitals. Pros: 4000-4500K is closest to natural light, the light is softer and can provide higher brightness while maintaining driver attention. Cons: Not as high visibility as above 5000K.
Lights with Kelvin temperatures in the range of 4500K-6500K are called cool white light, producing a fresh color similar to sunlight. These lights are best when maximum illumination is needed, such as for safety lighting, display cabinets, warehouses, and industrial areas. Highest visibility reduces accidents, especially those above 5700K, are popular for engineering projects. Cons: Can cause fatigue and should not be used in long-term workspaces.
LED Solar Street Light CCT Standards
In most countries, four common color temperature options for LED lights are 2700K (some manufacturers write it as 3000K), 3000K, 3500K, 4000K, 5700K (some manufacturers write it as 6000K), with other color temperatures being customized.
Road Lighting Color Temperature Illumination Ranges
Highway Lighting CCT
Some countries’ regulations (such as China) specify that the color temperature should not exceed 5000K, preferably choosing a medium to low color temperature. However, many engineering projects in various countries still choose 5700K or even above 6000K because the advantages of high color temperature are also significant, improving visibility and reducing accidents.
Color Temperature Requirements for Airport Road Lighting
According to the technical standards for civil airport flight areas, when using LED as a light source, a lens should be added to control glare, and the color temperature should not exceed 4000K.
Residential Area Road Lighting CCT
For roads with mixed motor vehicle and pedestrian traffic in residential areas, it is advisable to use light sources with low to medium color temperatures, most commonly kept below 4000K.
Color Temperature Requirements for Roads with Rain and Fog
Lights along rivers and foggy road sections should use low color temperature lights, with a recommended range of 2700K-3500K.
Commercial Area Road Lighting Color Temperature
In commercial bustling areas, historic and cultural districts, scenic spots, and other places where color recognition is important for motor vehicle traffic, it is advisable to use high CRI, low to medium color temperature light sources.
Parking Lot Road Lighting CCT
5700-6500K is preferable. A 5700K color temperature can help focus attention and make driving safer.
Color Temperature Requirements for Garden and Industrial Lighting
Spotlights, outdoor floodlights, and other landscape lights used in gardens, road decorations, partial lighting, and other outdoor recreational areas. Generally, warm colors of 2700K and 3000K are more suitable, creating a warm and relaxing atmosphere.
Understanding Watts and Lumens: How to choose the right brightness light fixture for your project
Lumens vs watts
What does watts mean in light bulbs?
Watts (symbol: W) is a unit of power, measuring the amount of energy consumed. When we pay our electricity bill, we are paying for the watts we use. Since we have traditionally used incandescent light bulbs, we are accustomed to using watts as a unit of brightness, but this is incorrect. The measure of the brightness of a light fixture is lumens, not watts.
Understanding Lumens
Lumens are the measurement of visible light energy. The higher the number of lumens, the brighter the light. Lighting fixtures used for illumination are usually labeled with their light output (in lumens), which is legally required in many jurisdictions.
Therefore, when we choose the brightness of the lamp, we only need to look for the lumen value on the package.
Understand the conversion between lumens and watts to find the right brightness
If a road contractor asks if we have a 100W solar street light, it is difficult to determine the requirement for how many lumens of solar LED street light they need. To understand the relationship between them clearly, we need to understand Luminous Efficacy (lumens per watt).
This measure indicates how efficiently a light source converts energy (watts) into light (lumens).
Luminous efficacy (lm/W) = lumens (lm)/Watt(W)

Luminous efficacy of different lamps with the same watt
Luminous efficacy of different lamps
Based on a 2013 report from energy.gov in the United States, there are LED package standards established at 266 lm/W and PC-LEDs achieving over 130 lm/W, with a successful prediction that by 2024 the luminous efficacy of LEDs will exceed 200 lm/W, showing the importance and expectations for future LED lighting.
As of 2024, LED technology can indeed achieve a theoretical 230 lm/W (actual usage tested at 200 lm/W). Due to variations in specifications among manufacturers and market supply-demand issues, there are still many LEDs on the market ranging from 130 lm/W to 190 lm/W. Therefore, when selecting the brightness of a light fixture, it is essential to pay attention to lumens.
Incandescent technology typically produces 12-18 lumens per watt, while halogen technology usually produces 10-20 lumens per watt.
Therefore, for the same wattage, the brightness of LED bulbs is approximately 10-14 times that of incandescent bulbs and about 10 times that of halogen bulbs. You can roughly refer to this indicator when choosing light fixtures.
lumens to watts conversion chart (in led light Luminous efficacy 130 lm/W)
Lumens | Incandescent Watts | Halogen Watts | LED Watts |
100 | 7 | 6 | 0.77 |
375 | 25 | 20 | 2.9 |
450 | 30 | 25 | 3.5 |
800 | 60 | 45 | 6 |
1100 | 75 | 60 | 8.5 |
Lumen to watt chat (In different led Luminous efficacy)
Lumens to watt | Luminous efficacy(lm/W) | |||
Lumens | 130 lm/W | 150 lm/W | 180 lm/W | 200 lm/W |
100 lm | 0.8w | 0.7w | 0.6w | 0.5w |
500 lm | 4w | 3w | 3w | 3w |
1000 lm | 8w | 7w | 6w | 5w |
2000 lm | 15w | 13w | 11w | 10w |
3000 lm | 23w | 20w | 17w | 15w |
4000 lm | 31w | 27w | 22w | 20w |
6000 lm | 46w | 40w | 33w | 30w |
8000 lm | 62w | 53w | 44w | 40w |
10000 lm | 77w | 67w | 56w | 50w |
15000 lm | 115w | 100w | 83w | 75w |
20000 lm | 154w | 133w | 111w | 100w |
How to verify the reliability of Luminous Efficacy
Rely on the manufacturer’s provided Luminous Efficacy Test Report.
How do I know how many lumens I need?
Lumen calculator
You can use a lumen calculator to determine this, at https://www.omnicalculator.com/everyday-life/lighting
How many lumens are needed for outdoor street lights?
The number of lumens required for street lights depends on several factors, such as the height of the light pole, the width of the road, and the amount of ambient light available. To determine the appropriate lumen output, recommended illumination levels for different types of roads need to be considered.
Generally, residential streets require around 5,000 to 12,000 lumens per light, while main roads and highways may require higher lumen outputs, typically needing 10,000 to 15,000 lumens to ensure safety.
Reference Standards for street lights Pole Height and Lumen
- 6m Height:6000Lumens
- 8m Height:8000Lumens
- 10m Height:10000Lumens
- 12m Height:12000Lumens
- 14m Height:15000Lumens
- 16m Height:18000Lumens
- 20m Height:25000Lumens
For guidance on how to choose the light pole height, please refer to the article:HOW TO CALCULATE THE HEIGHT AND DISTANCE OF SOLAR STREET LIGHT POLE?
How many lumens are needed for indoor environments
- Workspace or garage: 8,000 to 10,000 lumens
- Kitchen work areas: 7,000 to 8,000 lumens
- Bathroom: 7,000 to 8,000 lumens
- Home office: 6,000 to 8,000 lumens
- Dining room: 3,000 to 4,000 lumens
- Kitchen: 3,000 to 4,000 lumens
- Dining room: 3,000 to 4,000 lumens
- Living room: 1,000 to 2,000 lumens
- Bedroom: 1,000 to 2,000 lumens
- Hallway: 500 to 1,000 lumens
These are general guidelines that apply to most spaces; however, they may not be applicable to all scenarios. Rooms with darker walls and particularly high ceilings may require additional lumens to achieve the desired effect.
Finally, we recommend you read this article to learn about Light measurement for solar street lighting systems:https://luxmanlight.com/are-solar-street-lights-bright-enough/
Sources of reference
https://en.wikipedia.org/wiki/Lumen_(unit)
https://en.wikipedia.org/wiki/Watt