The wattage of street lights can range from 30 W to 300 W, depending on different light sources and applications. Street light wattage is the first thing you will think about when choosing street lights. Street lights with the right wattage can not only provide bright illumination but also avoid energy waste. What should be the wattage of street lights for different applications? How to choose the wattage of HPS-equivalent LED street lights? How many watts will they consume? The following guideline on street light wattage contains all of the information you need!
How to convert the wattage of LED, HPS, fluorescent, and incandescent street lights?
| Light source | LED | HPS | fluorescent | incandescent |
| Light efficiency(lm/w) | 110 | 100 | 80 | 20 |
| Power factor | 90% | 85% | 85% | 100% |
| Light utilization efficiency | 90% | 60% | 60% | 60% |
| Light that passes through the housing | 90% | 60% | 60% | 60% |
Light utilization efficiency: Light sources have different light distribution designs. If the design is not reasonable enough, there will be light emitting outside of the roads or going in the wrong direction. As a result, the light utilization efficiency of this kind of street light is low.
From the table, we can determine the actual efficiency of the light sources:
LED: 110*0.9*0.9*0.9=80.19 lm/w
High pressure sodium: 100*0.85*0.6*0.6=30.6 lm/w
Fluorescent: 80*0.85*0.6*0.6=24.48 lm/w
Incandescent: 20*1*0.6*0.6=7.2 lm/w
The actual efficiency of LED street lights is 2.6 times higher than HPS lights, 3.3 times higher than fluorescent lights, and 11 times higher than incandescent lights.
Therefore, we can convert the wattage of HPS and LED according to their efficiency:
150 W HPS street lights≈60 W LED street lights
250 W HPS street lights≈100 W LED street lights
400 W HPS street lights≈150 W LED street lights
How many watts are street lights for different applications?
- Roadway street lights: For roadways, common street lights are 250 W to 400 W HPS street lights and 100 W, 110 W, 120 W, 150 W, 200 W, 250 W, and 300 W LED street lights. And the average wattage for street lights is 80 W. The roadways often carry heavy traffic, so the lighting standards are high. If applying HPS lights, the power needs to be high. But normally, LED lights are the better choice because of their high efficiency. They can achieve the same lux level at a lower power. Since the main roads and secondary roads have different traffic and standards, the lights for them have different wattage. For instance, the main roads may need 400 W HPS street lights, while 250 W HPS lights are enough for the secondary ones.
- Landscape/residential/rural street lights: Landscape street lights don’t need to provide very bright light, thus the wattage of LED street lights is generally 30-100 W.
- Industrial street lights: The LED street lights in common industrial parks are similar to those on city roads. Usually, they can be 6 to 8- meters -high, and the watts can be 50-100 W. But for special areas like the ports, they apply high mast lights, which can be 20 to 50- meters -high, so the wattage is also higher. The wattage of them can be 200-500 W.
How many kilowatts do street lights consume?
We can compare the most popular 400 W HPS street lights and their equivalent 150 W LED street lights to calculate how many kilowatts they will use in a year. Suppose the lights work for 10 hours every day.
HPS: 0.4 KW*10 H*365 D=1460 KWH
LED: 0.15 KW*10 H*365 D=547.5 KWH
How to calculate the right street light wattage?
Step 1: Find out the total luminous flux
Luminous Flux (lm) = Illuminance (lx) × Area (m²)
The power of the lamp depends on how bright the road needs to be, that is, Luminous Flux. The total luminous flux can be obtained by using the illuminance standards of different countries * the area of the road to be illuminated.
- Calculate the total illuminated area
Take a road with a length of 900 meters and a width of 10 meters as an example, the total area of the road is 900 m × 10 m = 9,000 m².
- Calculate the total luminous flux
The common road illuminance standard is 20-30 lx. Here we use 20 lx for calculation, and the total luminous flux will be 20 lx × 9,000 m² = 180,000 lm. That is to say, the street lamps installed on this road need to provide a total of 180,000 lm of light.
- Calculate the luminous flux a single street lampshould provide
To find out the luminous flux of a single street lamp, you need to know the number of street lamps. Number of street lights = total length of road / street light spacing. Street light spacing is most related to height. You cab read this blog to learn more about the relationship between spacing and height. For common 8 m street lights, the spacing is generally 30 m. So there are 30 street lights on this 900 m road. The luminous flux provided by each street light should be 180,000 lm/30 m=6000 lm.
Step 2: Calculate the power
The formula for calculating power is Power (W) = Total Luminous Flux (lm)/Luminous Efficacy (lm/W).
The current Luminous Efficacy of LED street lights can basically reach more than 100 lm/W. If the Luminous Efficacy of a street light is 100 lm/W, the power of the street light is 6000 lm/100 lm/W=60 W.
Conclusion
From this comprehensive guide about street light wattage, you can learn how to convert the wattage of different light sources, the common wattage of the street lights in different applications, how much power the lights consume, and how to specifically calculate the wattage. After knowing the wattage you should choose, there are other things to consider, like the height, light distribution, etc. Check out our blogs for additional useful information, or contact us directly!
