Low-Pressure Sodium Lighting

Low-pressure sodium lamps provide the most energy-efficient outdoor lighting compared to high-intensity discharge lighting, but they have very poor color rendition. Typical applications include highway and security lighting, where color is not important.

Low-pressure sodium lamps work somewhat like fluorescent lamps. Like high-intensity discharge lighting, low-pressure sodium lamps require up to ten minutes to start and have to cool before they can restart. Therefore, they are most suitable for applications where they stay on for hours at a time. They are not suitable for use with motion detectors.

You can use the chart below to compare low-pressure sodium lamps with high-intensity discharge lamps. This chart can help you understand basic lighting principles and terms.

Lighting Type

Efficacy
(lumens/watt)

Lifetime
(hours)

Color Rendition Index
(CRI)

Color Temperature
(K)

Indoors/Outdoors

High-Intensity Discharge
Mercury vapor

25–60

16,000–24,000

50 (poor to fair)

3200–7000 (warm to cold)

Outdoors

Metal halide

70–115

5000–20,000

70 (fair)

3700 (cold)

Indoors/outdoors

High-pressure sodium

50–140

16,000–24,000

25 (poor)

2100 (warm)

Outdoors

Low-Pressure Sodium

60–150

12,000–18,000

-44 (very poor)

Outdoors