The luminous efficiency of LED street lamp and high pressure sodium lamp is similar. Why can LED street lamp replace the high power sodium lamp with lower power? How is it converted? The following is a personal view, it is inevitable that there are imperfections, please ask me to correct.

High pressure sodium lamp belongs to point light source, which is 360 degree light emitting. In fact, the light applied to the direction of the radiation is very small, only about 30%. Therefore, the high pressure sodium lamp must reflect the light in the non irradiation direction through the reflector in the lamp, so as to achieve the purpose of higher light utilization. Due to the lamp design and cost problem, the efficiency of sodium lamp is only 40-45%.

The LED street lamp / tunnel lamp belongs to the area light source, the luminous surface is a single direction, the light source utilization rate is high, and the lamp efficiency is above 80%.

Here we take 100W LED street lights and 250W high pressure sodium lamp as an example to illustrate this problem.

1. Initial luminous flux of 100w LED street lamp 11000lm. Because the lens loss is 10%, the power loss is 10%, the luminous flux of the lamp is actually 8910lm, and the total power consumption of the lamp is 110W. So the light effect of this LED street lamp is 81lm/W.

2. The initial luminous flux of 250W high pressure sodium lamp is 25000lm, the light source utilization loss is about 30%, the power loss is about 20%, and the luminous flux is 12500lm, the total power consumption of the lamp is about 300W. So the light effect of this high pressure sodium lamp is 41.67lm/W.

Through the above analysis and comparison of the final luminous efficiency value, we can find that the luminous efficiency of 100w LED street lamp is almost 2 times higher than that of 250W high-pressure sodium light. This is why 100W LED street lamps can be used instead of 250W HPS lamps.