Preface
In recent years, LED lighting has made great progress in terms of cost and performance. Compared with traditional light sources, LED lighting has obvious advantages like energy-saving effects, long service life (up to 100,000 hours), small size, and easy control. This article evaluates the feasibility of using LED lights for street lighting from both technical and economic perspectives.
Overview of LED Lighting Technology
LED lighting, also known as solid-state lighting, currently has six major applications: LED displays, backlighting, automotive lighting, interior decoration, landscape lighting, and commercial lighting.
Overview of LED Streetlights
Among the applications of LED lighting, LED streetlights have the most direct and immediate impact on people’s production and daily life.
Introduction to LED Streetlight Products
There are many manufacturers of LED streetlights on the market who launched their own products. Various LED streetlight products have brought great convenience to people’s lives. Below we introduce several important players in the LED streetlight field.
As early as 2003, the US company Mooncell began producing LED streetlight products, among which Econo-LumTM is the best-selling one. In the field of lighting, Philips is naturally an important player. Philips began to launch its own LED streetlight products in 2005. And its multiple Eda LED streetlight products have been installed on many streets in Europe. MOKOlight also joined the LED streetlight product development in 2006 and launched multiple successful LED streetlight products in 2007. With the accumulation of technology, MOKOlight’s LED streetlights now have leading performance in the industry.
Road Lighting Standards
Every country has its own lighting standards. Let’s take China’s lighting standards as an example. China’s road lighting standards, Article 2.0.1, divides roads into five levels: expressways, trunk roads, secondary trunk roads, branch roads, and residential areas.
| Level | Road Type | Brightness | Illuminance | Glare Restriction for Non-cutoff fixtures | Induction | ||
| Average Brightness Lav(Cd/m²) | Uniformity Lmin/Lav | Average Illuminance Eav(Lx) | Uniformity Emin/Eav | ||||
| Ⅰ | Expressway | 1.5 | 0.4 | 0.4 | 0.4 | Strictly prohibited | Pretty Good |
| Ⅱ | Main roads, welcome roads, main roads leading to government buildings and large public buildings, city centers or commercial center-type interchange nodes, etc. | 1.0 | 0.35 | 1.5 | 0.35 | Strictly prohibited | Pretty Good |
| Ⅲ | Secondary roads | 0.5 | 0.35 | 8 | O.35 | Not allowed | Good |
| Ⅳ | Branch roads | 0.3 | 0.3 | 5 | 0.3 | Not recommended | Good |
| Ⅴ | Residential roads and sidewalks mainly used by pedestrians and non-motorized vehicles | — | — | 1-2 | — | Not restricted | — |
Note:
① The average illuminance listed in the table is only applicable to asphalt roads. If it is a cement concrete road surface, the average illuminance value can be reduced by 20-30% accordingly.
② The figures in the table only apply to dry road surfaces.
Analysis of the Costs of LED streetlights
Comparison of the costs of LED and conventional street lighting
Street lights are installed every 30 meters on each side of the road. So the total number of street lights needed for these three road sections is 202, 333, and 666 as we assume that a city has three road sections that are 3 kilometers, 5 kilometers, and 10 kilometers in length. Traditional street lights use 250W high-pressure sodium lamps, while LED street lights only use 50W!
Comparison of Street Light Costs
The unit price of traditional street lights is ￥1000 per light, and that of LED street lights is ￥3000. So the light source costs required for laying roads of the three lengths using traditional street lights are: 202*1000=202,000 RMB, 333*1000=333,000RMB, 666*1000=666,000RMB. And the light source costs required for laying roads of the three lengths using LED street lights are: 202*3000=606,000RMB, 333*3000=999,000RMB, 666*3000=1,998,000RMB (as shown in Table 1).
Table 1 – Comparison of Street Light Costs | ||
| Distance | Traditional Street Lights | LED Street Lights |
| 3km | ¥ 202,000 | ¥ 606,000 |
| 5km | ¥ 333,000 | ¥ 999,000 |
| 10km | ¥ 666,000 | ¥ 1,998,000 |
Comparison of Cable Installation Costs
The prices of cables of different lengths vary. Below, we compare the cost of cables for 3 km, 5 km, and 10 km roads.
For the main line of 3 km street lamps, the cost of cables used for traditional street lamps is 120*3000=360,000RMB. For LED street lamps, a current of 44A is required for normal operation, so they use 10mm² copper core cables. The cost of cables used for 3 km LED street lamps is 12RMB/m, which amounts to 36,000RMB.
For the main line of 5 km street lamps, the cost of cables used for traditional street lamps is 180*5000=900,000RMB. For LED street lamps, a current of 73A is required for normal operation, so they use 20mm² copper core cables. The cost of cables used for 5 km LED street lamps is 25RMB/m, which amounts to 125,000RMB.
For the main line of 10 km street lamps, the cost of cables used for traditional street lamps is 360*10000=3,600,000RMB. For LED street lamps, a current of 146A is required for normal operation, so they use 42mm² copper core cables. The cost of cables used for 10 km LED street lamps is 60 RMB/m, which amounts to 600,000RMB.
The specific comparison can be seen in table 2 below.
Table 2 – Comparison of Cable Installation Costs | ||
| Distance | Traditional Street Lights | LED Street Lights |
| 3km | ¥ 360,000 | ¥ 36,000 |
| 5km | ¥ 900,000 | ¥ 125,000 |
| 10km | ¥ 3,600,000 | ¥ 600,000 |
Comparison of Electricity Consumption Cost for One Year
Let’s calculate the electricity consumption cost for one year. The calculation method assumes that the lights are on for 10 hours every day, and the cost of electricity is ￥1 per kWh.
For a 3 km road, the traditional street lamps consume 202 lamps * 10 hours * 365 days * 250W = 184,325,000W, which is equivalent to 184,325 kWh, costing ￥184,325. The LED street lamps consume a total of 202 lamps * 50W * 10 hours * 365 days = 36,865,000W, which is equivalent to 36,865 kWh, costing ￥36,865.
For a 5 km road, the traditional street lamps consume a total of 333 lamps * 250W * 10 hours * 365 days = 303,862,500W, which is equivalent to 303,863 kWh, costing 303,863 RMB. The LED street lamps consume a total of 333 lamps * 50W * 10 hours * 365 days = 60,772,500W, which is equivalent to 60,773 kWh, costing 60,773 RMB.
For a 10 km road, the traditional street lamps consume a total of 666 lamps * 250W * 10 hours * 365 days = 607,725,000W, which is equivalent to 607,725 kWh607,725 RMB. The LED street lamps consume a total of 666 lamps * 50W * 10 hours * 365 days = 121,545,000W, which is equivalent to 121,545 kWh, costing 121,545 RMB. The comparison is shown in Table 3.
Table 3 – Comparison of Electricity Consumption Cost for One Year | ||
| Distance | Traditional Street Lights | LED Street Lights |
| 3km | ¥ 184,325 | ¥ 36,865 |
| 5km | ¥ 303,863 | ¥ 60,773 |
| 10km | ¥ 607,725 | ¥ 121,545 |
Comparison of Light Source Lifespan
We selected the widely used high-pressure sodium lamp and compared it with LED street lamps. The best high-pressure sodium lamp on the market has a lifespan of 3000-4000 hours. And the lifespan of LED light sources can exceed 30,000 hours. This is more than seven times longer than the best high-pressure sodium lamps on the market. From this data, we can see that LED street lamps have a longer lifespan. Besides, the maintenance is simple and the cost is relatively low. Although the price of LED lights may be more expensive than high-pressure sodium lamps, they last for longer time. For street lamps with a long lifespan, the longer they work, the more cost-effective they become.
Total Cost Comparison
Please refer to Table 4 and Table 5 for the total cost comparison for the three lengths of roads.
Table 4 – One-Year Installation Cost Comparison | ||
| Distance | Traditional Street Lights | LED Street Lights |
| 3km | ¥ 746,325 | ¥ 678,865 |
| 5km | ¥ 1,536,863 | ¥ 1,184,773 |
| 10km | ¥ 4,873,725 | ¥ 2,719,545 |
Table 5 – Five-Year Installation Cost Comparison | ||
| Distance | Traditional Street Lights | LED Street Lights |
| 3km | ¥ 1,483,625 | ¥ 826,325 |
| 5km | ¥ 2,752,315 | ¥ 1,427,865 |
| 10km | ¥ 7,304,625 | ¥ 3,205,725 |
Analysis of the Cost of Street Light Transformation
The unit price of traditional street lamp heads is ￥250 per unit, while that of LED light heads is ￥2200. Therefore, the cost of LED light source for the transformation of three different road lengths are: ￥444,400 for 202 pieces, ￥732,600 for 333 pieces and ￥1,465,200 for 666 pieces respectively. The initial investment is relatively large, but it will be quickly recovered in electricity bills! Thus to say that LED costs much can be one of the myths about LED lights. Please refer to table 6 for details.
Table 6 – Cost of Street Light Transformation | |||||
| Electricity Cost Per Year | Difference in Electricity Cost Per Year | Renovation Cost | Payback Period | ||
| Distance | Traditional Street Lights | LED Street Lights | |||
| 3km | ¥ 184,325 | ¥ 36,865 | ¥ 147,460 | ¥ 444,400 | 3.01 Years |
| 5km | ¥ 303,863 | ¥ 60,773 | ¥ 243,090 | ¥ 732,600 | 3.01 Years |
| 10km | ¥ 607,725 | ¥ 121,545 | ¥ 486,180 | ¥ 1,465,200 | 3.01 Years |
Note: If the electricity price is ￥0.75/kWh instead of ￥1.00/kWh, the payback period will be 4.01 years instead of 3.01 years.
In the comparison above, 50W LED street lamps are compared to 250W HPS bulbs. Street lamps powered by 70W LEDs are equivalent to 400W high-pressure sodium lamps. The benefits of LED street lights are obvious and increase with usage time.
Conclusion
The development of LED technology is advancing by leaps and bounds. Although the price of LED lights is still relatively high, their economic applicability on street lamps is obvious. According to Caroline Fan, the Chief Operating Officer of MOKO technology, LED lights with relatively fair prices, longer lifespan, and ultra-high brightness white light are suitable for large-scale deployment, especially for street lamps. We believe that the era of LED lighting has arrived.
