Idea #318 – Reduce Streetlight and Outdoor Lighting Brightness

Report Status: Fully Reviewed

Researched by: Travis Franck

Idea Text

Have Belmont Light turn their newly installed led lights down by 1/2. People I have talked to about their new streetlights complain that they are way too bright. Tim Brothers, manager of the MIT Wallace Astrophysical Observatory and Vice President of the Massachusetts chapter of the International Dark Sky Association, in the video link below talks about all the important environmental and health benefits of turning down the lights. Kudos to the Light Dept. for installing the new healthier led bulbs. Tim Brothers makes 2 more comments in this video that might be relevant: 1) 2700k bulbs are healthier (I believe Belmont is using 3000k); and 2) the town of Westford, MA turned their streetlights down by 50% and no one even noticed!

Other ideas included in this report

  • 318 – Reduce LED street light brightness

  • 282 – Reduce light usage on town fields and facilities

  • 288 – Reduce brightness of Wellington lightening

Idea intent

SCIG considers the suggestions to ask the town and Belmont Light to assess whether there could be new lightening settings that change the brightness, the timing, and the efficiency. These changes could reduce costs, reduce emissions, and improve the quality of life for neighbors of these facilities.

Weighted Final Score: 54 (Financial Impact: 3, Operational Impact: 2, Time Scale: 4, Ease of Implementation: 4)

Background Information

The streetlights of Belmont are owned and maintained by Belmont Light. The lights for parks and fields near schools are on the respective school circuits (“behind the meter” of the nearby school building). The Town pays for the streetlight electricity and pays for the light fixtures and electricity at the parks/fields. The savings for streetlights and field lights would differ because they are charged two different prices of electricity. For reference, the current rate for municipal streetlighting is $0.25853 per kWh.

Belmont Light began upgrading the streetlighting system from high-pressure sodium bulbs to LEDs bulbs in 2019. This conversion from reduces the energy use of streetlighting about 40% (70W to 40W). As of January 2022, Belmont Light has upgraded about 70% of the streetlights in Belmont. Belmont Light chose LED fixtures that emit 3000K temperature light after considering 2700K, 3000K, 4000K. The decision was made after considering energy efficiency, aesthetics, public safety, and cost (2700K streetlights weren’t being produced at scale). The new LED streetlights can be independently controlled from a central location (i.e., remotely), including setting the brightness. Belmont Light initially sets the new LED bulbs to 100%. A limited number of bulbs have been remoted dimmed based on neighborhood feedback.

Proper lighting of streets and walkways is primarily a public safety issue. Belmont Light stated they are willing to adjust streetlighting brightness but would like to work with the Police Dept and relevant town officials to decide the best course of action.

Financially, the town spent $298k in 2019 and $258k in 2020 on streetlighting electricity costs (Belmont Light Audited 2020 Statement, pg. 44). The decrease in costs from 2019 to 2020 could be because of the active LED conversion. To estimate the potential savings from dimming streetlights, let’s assume that, after 100% conversion, the annual streetlight electricity costs are around $240k (ballpark). Also, assuming a linear savings in energy costs (dimming 10% saves 10% of electricity), the potential savings of dimming all the streetlights in town would be:

Light Brightness Dimmed by Annual Savings
100% 0% $0/year
90% 10% $24,000/year
75% 25% $60,000/year
50% 50% $120,000/year
30% 70% $168,000/year

To score this idea, the semi-conservative value of 75% was used, with the rationale that some streetlights could be dimmed more and others less based on public safety considerations. It is noted that the submitted idea text suggested that 50% was reasonable based on another community’s experience and, if implemented, would save Belmont more money.

Field and exterior school lighting is more difficult to estimate. Belmont Light commented that these lights are not LED and there current are no plans to convert them to LED. They are owned and operated by the School Department and the Department of Facilities. If those bulbs are still the older high-pressure sodium bulbs, there could be large savings from converting them to LED and then programming them with lower output (dimming) and potentially different on/off schedules. There would be an upfront cost to convert the bulbs, but with a corresponding on-going annual energy savings (approx. 40% using the streetlight figure above).

Recommendations

  • Belmont’s streetlights should be adjusted by Belmont Light in conjunction with Town public safety personnel. The process of dimming the new LED streetlights is straightforward since it is centrally controlled via software. The speed of implementation depends on the bandwidth of the individuals involved.

  • The annual costs savings could be significant and would be reoccurring every year ($500k-$1mil over 10 years).

  • The Department of Facilities should review lightening at fields and parks and budget to upgrade lighting for on-going energy and maintenance savings. This could be part of an Energy Service Company (ESCO) project (Idea #302).

  • There would be additional cost savings if the field and building lights were also managed differently.

Next Steps

  • The Town Administrator and/or the Select Board should instruct the Police Department and the Facilities Department to work with Belmont Light to adjust the brightness of streetlights.

  • One possible first step is to review any standard recommendations for streetlighting lumens and to adjust the LED lights to output this lumen brightness. Lighting is location-specific so adjustments might need to be made. Additionally, this is a first step and brightness could be further lowered and should be reviewed.

  • The default setting of new installations should not be 100%, but instead should be significantly lower.

  • Separately, the Facilities Department should examine field and exterior lightening fixtures and consider upgrading the lights to LEDs that could also be centrally controlled.

Further Reading