Saving energy with street lighting - how does it work?

13.10.2022

Since the energy shortage / energy crisis threatens, the street lighting has become the focus of the media and politics. Every kilowatt hour counts - so the tenor.

To the point: public lighting can make a valuable contribution to saving energy.

Up to 50% savings are possible by refurbishing lighting fixtures to modern LED lamps
Another 50% can be achieved through sensible dimming - in the best case, through a demand-oriented lighting control which is based, for example, on the volume of traffic.
Special attention needs pedestrian crossings and intersections. Because there light helps to significantly reduce the risk of accidents.

Because the refurbishment to LED street lights and a sensible dimming an energy saving of over 75% is possible, we recommend - for the sake of the safety of road users - where possible to do without night shutdown and instead dim as needed.

How much energy does public lighting consume in Switzerland?

Thanks to the continuous switch to energy-efficient LED luminaires, the energy consumption of public lighting in Switzerland has been continuously reduced from 468 GWh to 319 GWh / year since 2002 and accounted for 0.55% of Swiss electricity consumption in 2021. In comparison, Swiss households consume 20'134 GWh / year, which corresponds to 34.6% of the electricity consumed in Switzerland in 2021 (source: SFOE, Swiss Electricity Statistics 2021).

How can you save energy in street lighting?

To make public lighting as energy efficient as possible, two basic requirements should be met:

Renovation to efficient LED fixtures - these use at least 50% less energy than conventional fixtures
Time-dependent dimming - stored dimming profiles per luminaire (autonomous via Dynadimmer, or simple and efficient via central lighting control system)
Motion-dependent dimming - Sensors enable movements and traffic volume to be detected and the streets to be illuminated as required. This flexibly adjusts the brightness of the lighting

The most important contribution to saving electricity in public lighting is made by LED technology. Compared to conventional luminaires (e.g. high-pressure sodium lamps), more than 50% of energy consumption can be saved by converting to LEDs.

With the targeted dimming of the lights, energy consumption can even be reduced by up to 75% .

What do I need to know about switching off street lighting at night?

When it comes to saving energy across the board, lighting quickly attracts attention. This is understandable, because every area of life in which people move and stay even in the dark is illuminated with light.

Street lighting and road safety

Because light in road traffic ensures that road users have better visibility, safety is increased for all involved and the risk of accidents is reduced. Therefore, the lighting of roads is a component of the safety device. Measures that affect lighting are thus always to be evaluated taking into account the guarantee of safety and the applicable standard (SN EN 13201, supplemented by SLG 202 guideline).

Technical possibilities of the existing lighting infrastructure (H3)

In Switzerland, night shut-offs (e.g. between 01.00h and 05.00h) are practiced in many smaller communities. This usually involves interrupting the power to the luminaires, i.e. the phases for operating the luminaires are switched off centrally, e.g. via ripple control. This results in two different operating times per night:

Operation eve
Switch-on time at darkening (e.g. 19.30 o'clock) to night switch-off time (e.g. 01.00 o'clock)

Early morning operation
Switch-on time point early morning (e.g. 05.00) to switch-off time point dawn (e.g. 07.00)

For this purpose, the operation is switched from "all-night" (GN) to "half-night" (HN). This is not easily done with stand-alone LED luminaires with programmed dimming profiles.

Why this is so, you will learn in the article:

Night shutoff: Dynadimmer vs. networked luminaires with OLC

Do you have questions about turning off & controlling street lights?

We are happy to provide you with advice and support.

Jörg Imfeld

Head of Light Academy, member of SLG Street Lighting Expert Group, member of SLG Light Emission Expert Group contact

Questions & answers about night shut-off and dimming of street lighting

Can street lights simply be switched off? What says the street lighting standard and the SLG guideline?

The street lighting is a component of the safety equipment of a road. The standard SN EN 13201 regulates the lighting in the switched-on state. In it, the dimming due to the volume of traffic is also treated. Switch-offs are not part of the standard, and SLG can only make recommendations on this.

What do the laws say on the subject of street lighting and switching off?

In Switzerland, there is the national road law (741.01) and the cantonal road traffic laws.

At the cantonal level, street lighting is mentioned in the law and classified as a safety component of a road. Some cantons have further regulations that specify the issues related to street lighting (ordinances and/or lighting regulations, e.g., in the canton of Aargau).

If, for example, at 03.00 no traffic is present, can yet simply be switched off?

Shutdowns are the responsibility of the competent authority, usually the cantonal civil engineering office or the municipal construction office. Street lights that are present but temporarily not operated, change the legal situation on a road. Since lighting is a component of the safety installation, shutdowns should be carefully and soundly examined in advance.

If the street lighting is off from 01.00 - 05.00 and an accident occurs during this time, can the canton or the municipality be prosecuted?

If there is sufficient reasoning to justify the night shutdown, the canton or municipality has classified their roads as "safe to use" during this time. Shutdowns without prior clarification are not recommended.

What about the pedestrian crossings - should / can these also be switched off?

No, here it is recommended that the pedestrian crossings are correctly illuminated according to SLG 202 - guideline throughout the night. In addition, the lighting should remain switched on over both stopping distances* to the pedestrian crossing.
*Depending on the speed. In the range 50 km/h: stopping distance to the pedestrian crossing = 40m

What else must be observed when you want to switch off?

Clarified should be...
... the existing legal basis
... the hourly traffic volume over the night
... the schedules of public transport
... the safety perception of the population
... experience with accidents and crime
... technical possibilities to dim the lighting according to demand (via sensors) or time-dependent
... alternatives, such as providing the dimming profile of LED lights with a basic level

What happens to the LED luminaires with Dynadimmer when they are switched off?

The dynadimmers built into the lights and drivers require voltage to function properly throughout the night. If they are switched off, for example, between 01.00 - 05.00 clock, they come from the rhythm and can no longer determine the necessary artificial midnight. Thus, the luminaire no longer dims correctly, i.e. the dimming does not occur at the correct time or the luminaire remains at 100%. It is recommended to re-parameterize the Dynadimmer on site so that the dimming profile is set to 0% in the time between 01.00 - 05.00.