I live in a "Dark Sky" neighborhood in Mesa, Arizona. Mesa is part of the sprawling Phoenix metro area, a massive city in the western U.S. To our east lies a national forest, while to the west is the city. Due to the brightness of Phoenix, we can only see the brightest stars to the west. However, our eastern view offers a good look at the night sky, considering how close we are to the rest of the city.
In keeping with Dark Sky principles, our area has fewer streetlights, and they're designed with shields to minimize skyward glare. Homeowners are also restricted to using exterior lights of 800 lumens or less (equivalent to 60-watt incandescent bulbs) in warm white only.
What Does This Setup Get Us?
- Increased use of home outdoor lighting: People tend to leave their outdoor lights on longer to compensate for the dark streets.
- Darker streets: Reduced street lighting makes it challenging to see pedestrians and critters at night, even with modern headlights.
- Other hazards: The lack of sufficient lighting is a challenge for bikers and pedestrians.
Does It Save Money?
Let's break it down:
A typical LED streetlight uses about 120 watts, lighting the area in front of around 8 homes. If each of these 8 houses uses three 8-watt LEDs (60-watt incandescent equivalent), that's 24 watts per house or 192 watt-hours each for an extra 4 hours of use each night. Multiplied by 8 houses, this is 1,536 watt-hours, compared to 960 watt-hours for a single streetlight over 8 hours, and with the street light you get coverage all night.
Cost Comparison of Streetlight vs. Household Lighting
Streetlight Costs:
Total installation: $2,000 - $5,000, including the pole.
Lamp replacement: The lamp itself costs around $200 and lasts 20-25 years, while the pole (the most expensive part) lasts significantly longer.
Household Lighting Costs:
Bulbs: An 8-watt LED costs around $2.50, lasting about 5 years outdoors. Each house here uses 3 bulbs, which for 8 houses, costs around $60 every 5 years, or $120 over 10 years.
So, we’re looking at $100 for streetlight hardware over 10 years versus $120 for residential bulbs.
So, all else being equal and in short, it seems that streetlights are more cost effective over time due to their efficiency and durability, not to mention the broader, safer coverage they provide.
Go figure.