Data center light pollution: DarkSky’s statement on responsible development

As the global demand for AI and cloud computing grows, the rapid expansion of data centers has become a major topic of debate in local zoning boards. While much of the conversation focuses on energy and water use, the impact of industrial light pollution on our nocturnal environment is a critical piece of the puzzle.

At DarkSky International, we believe that digital progress doesn’t have to mean the end of the night. Our goal is to protect the darkness for wildlife, for human health, and for the inspiration that comes from seeing a star-filled sky.

Does DarkSky oppose data centers?

We recognize that local communities must decide if a data center is the right fit for their economy and resources. However, DarkSky takes a firm stance on siting:

• We oppose facilities proposed in naturally dark locations, specifically those that threaten the integrity of International Dark Sky Places (IDSP). These “dark islands” are rare, and once lost to industrial skyglow, they are nearly impossible to recover.
• In developed areas, we don’t oppose the facility itself, but we advocate for the highest standards of lighting guided by the Five Principles of Responsible Outdoor Lighting at Night.

How to reduce light pollution from data centers: 4 key strategies

For facilities deemed appropriate for their location, light pollution can be mitigated by following ROLAN principles and technical standards like IES RP-43-22. We recommend four primary pillars for any industrial lighting plan:

1. Avoid over-illumination

Data centers often use “brute force” lighting for security. However, following professional standards, light levels should be kept to the absolute minimum necessary. If a space isn’t actively being used by humans, it shouldn’t be lit like a stadium.

2. Implement the 80-degree cutoff

Our municipal template now advocates for a 80-degree cutoff angle. This goes beyond “zero uplight”—it ensures the beam is tight and targeted. This prevents light from spilling horizontally into the neighborhood or creating the glare that actually hinders security cameras.

3. Use smart lighting controls

Data centers are high-tech hubs; their lighting should be too. We advocate for motion sensors and dimming to reduce light levels significantly during late-night hours when staff activity is minimal.

4. Prioritize warmer color temperatures (3000K or less)

Blue-rich white light scatters more easily in the atmosphere, increasing skyglow. We advocate for warmer color temperatures (up to 3000K) to protect the circadian rhythms of local wildlife and residents.

Technical sidebar: Recommended lux levels for data centers

Industry standards (such as IES recommendations) prove that safe, functional light levels are often much lower than many developers realize. Using these maintained illuminance levels in your local advocacy can prevent over-lighting:

• Parking lots: 2 lux (horizontal)
• Active transaction areas (pre-curfew): 10 lux (horizontal)
• Active transaction areas (post-curfew): 2 lux (horizontal)

Note: These levels provide ample visibility for security while protecting the night sky. Developers should refer to the relevant national standard, such as IES RP-8 (Lighting for Roadways and Parking Facilities) in the United States. [link]

Does dark sky-friendly lighting actually work?

The results of applying these principles are measurable and dramatic:

• Industrial success: In certain oil and gas applications, rigorous shielding and controls have reduced light pollution by 98% while saving 60% in annual energy costs. [link]
• Tucson’s example: After a massive LED streetlight retrofit using DarkSky principles and dimming, the city of Tucson, Arizona, reduced its total skyglow by 7%, even while the city continued to grow. [link]

Summary: A path forward

Data centers do not have to be beacons of light pollution. By following the ROLAN principles—using light only where it’s needed, when it’s needed, and in the amount needed—we can keep our data in the cloud and the stars in our sight.

Advocacy checklist for your community

If a data center is proposed in your area, ask the developers these three questions:

1. Does the plan include a lighting audit that follows ROLAN principles?
2. Are all fixtures rated for an 80-degree cutoff to prevent light trespass?
3. Will the facility use automated controls to dim or turn off lights after curfew?

Want to do more? Download our Municipal Template to help your city leaders draft stronger lighting ordinances today.