Actual energy savings when replacing high-pressure sodium with LED luminaires in street lighting

Numerous independent field research studies, trying to establish actual energy savings when replacing high-pressure sodium (HPS) luminaires with LED ones in street lighting, had serious deficiencies. Therefore, our approach was based on equal photopic or mesopic luminance levels when comparing street lighting installations. In addition, a novel approach, considering energy efficiency indicators of LED luminaires in both the standard and reduced lighting regimes, enabled the determination of their energy saving potential in various dimming scenarios. The stated requirements for a case street could represent guidelines for future pilot projects in this field. The comparison of the measurement results obtained using both the telemanagement system and electricity meters, which was done for the first time, showed that the former can enable reliable assessment of electrical parameters. It was concluded that when using quality LED instead of quality HPS luminaires energy savings could be between 31% and 60% when applying multi-stage dimming scenarios. An important finding is that the LED luminaire power factor can considerably decrease when reducing the luminous flux. Another important finding is that the increase of the street luminance level to its initial value in early morning hours only slightly increases the overall electricity consumption.