Switching a yellow traffic light from an incandescent bulb to an LED can result in significant cost savings, just like with red lights. To estimate the savings over the lifetime of the LED, we’ll follow a similar method as with the red light, but with a different wattage for the incandescent yellow light.
Assumptions for Calculation:
Here are the values we’ll use for both the incandescent yellow light and the LED yellow light:
Incandescent Bulb:
- Power Consumption: 135 watts (typical for a yellow incandescent traffic light).
- Lifespan: 8,000 hours.
- Cost per bulb: $5 (approximate cost of a yellow incandescent traffic light bulb).
- Operating Hours: 24 hours per day, 365 days per year (standard operation for traffic lights).
- Electricity Rate: $0.12 per kilowatt-hour (kWh) (this may vary by location).
LED:
- Power Consumption: 10 watts (standard for a yellow LED traffic light).
- Lifespan: 50,000 hours.
- Cost per LED module: $100 (average cost for a yellow LED traffic light module).
- Operating Hours: 24 hours per day, 365 days per year.
- Electricity Rate: $0.12 per kWh.
1. Energy Consumption and Cost of Incandescent Bulb:
Annual Energy Use:
135 watts×24 hours/day×365 days/year=1,182,600 watt-hours/year=1,182.6 kWh/year135 \, \text{watts} \times 24 \, \text{hours/day} \times 365 \, \text{days/year} = 1,182,600 \, \text{watt-hours/year} = 1,182.6 \, \text{kWh/year}135watts×24hours/day×365days/year=1,182,600watt-hours/year=1,182.6kWh/year
Annual Energy Cost:
1,182.6 kWh/year×0.12 $/kWh=141.91 $/year1,182.6 \, \text{kWh/year} \times 0.12 \, \text{\$/kWh} = 141.91 \, \text{\$/year}1,182.6kWh/year×0.12$/kWh=141.91$/year
2. Energy Consumption and Cost of LED:
Annual Energy Use:
10 watts×24 hours/day×365 days/year=87,600 watt-hours/year=87.6 kWh/year10 \, \text{watts} \times 24 \, \text{hours/day} \times 365 \, \text{days/year} = 87,600 \, \text{watt-hours/year} = 87.6 \, \text{kWh/year}10watts×24hours/day×365days/year=87,600watt-hours/year=87.6kWh/year
Annual Energy Cost:
87.6 kWh/year×0.12 $/kWh=10.51 $/year87.6 \, \text{kWh/year} \times 0.12 \, \text{\$/kWh} = 10.51 \, \text{\$/year}87.6kWh/year×0.12$/kWh=10.51$/year
3. Maintenance Costs:
Incandescent Bulb Replacement Frequency:
- Incandescent bulbs last 8,000 hours, so at 24-hour operation, they need to be replaced every:
8,000 hours÷(24 hours/day)=333.3 days8,000 \, \text{hours} \div (24 \, \text{hours/day}) = 333.3 \, \text{days}8,000hours÷(24hours/day)=333.3days
- Over the 50,000-hour lifespan of an LED, the incandescent bulb would need to be replaced 6.25 times.
Maintenance Costs for Incandescent Bulbs:
- Cost per replacement: $5 per bulb, plus approximately $50 for labor per replacement.
- Over the 50,000-hour lifespan of an LED:
6.25 replacements×(5 $ per bulb+50 $ labor)=343.75 $ total maintenance cost for incandescent bulbs6.25 \, \text{replacements} \times (5 \, \text{\$ per bulb} + 50 \, \text{\$ labor}) = 343.75 \, \text{\$ total maintenance cost for incandescent bulbs}6.25replacements×(5$ per bulb+50$ labor)=343.75$ total maintenance cost for incandescent bulbs
LED Maintenance Costs:
- LEDs last 50,000 hours, so no replacements are needed within this timeframe. Therefore, the maintenance cost for LEDs over the same period is $0.
4. Total Savings Over the Lifetime of the LED (50,000 hours):
Total Cost for Incandescent Bulb (50,000 hours):
- Energy Cost (over 50,000 hours):
50,00024×365×141.91 $/year=6.25 years×141.91 $/year=886.94 $ for energy\frac{50,000}{24 \times 365} \times 141.91 \, \text{\$/year} = 6.25 \, \text{years} \times 141.91 \, \text{\$/year} = 886.94 \, \text{\$ for energy}24×36550,000×141.91$/year=6.25years×141.91$/year=886.94$ for energy
- Maintenance Cost: $343.75
- Total Cost for Incandescent Bulb:
886.94 $ (energy)+343.75 $ (maintenance)=1,230.69 $ total cost886.94 \, \text{\$ (energy)} + 343.75 \, \text{\$ (maintenance)} = 1,230.69 \, \text{\$ total cost}886.94$ (energy)+343.75$ (maintenance)=1,230.69$ total cost
Total Cost for LED (50,000 hours):
- Energy Cost (over 50,000 hours):
50,00024×365×10.51 $/year=6.25 years×10.51 $/year=65.69 $ for energy\frac{50,000}{24 \times 365} \times 10.51 \, \text{\$/year} = 6.25 \, \text{years} \times 10.51 \, \text{\$/year} = 65.69 \, \text{\$ for energy}24×36550,000×10.51$/year=6.25years×10.51$/year=65.69$ for energy
- Maintenance Cost: $0
- Cost of LED Bulb: $100
- Total Cost for LED:
65.69 $ (energy)+100 $ (bulb)=165.69 $ total cost65.69 \, \text{\$ (energy)} + 100 \, \text{\$ (bulb)} = 165.69 \, \text{\$ total cost}65.69$ (energy)+100$ (bulb)=165.69$ total cost
5. Total Savings Over the LED’s Lifetime:
1,230.69 $ (incandescent cost)−165.69 $ (LED cost)=1,065 $ saved over the LED’s lifetime1,230.69 \, \text{\$ (incandescent cost)} – 165.69 \, \text{\$ (LED cost)} = 1,065 \, \text{\$ saved over the LED’s lifetime}1,230.69$ (incandescent cost)−165.69$ (LED cost)=1,065$ saved over the LED’s lifetime
Conclusion:
Switching a yellow traffic light from an incandescent bulb to an LED can save approximately $1,065 over the lifetime of the LED (50,000 hours). These savings come from the reduced energy consumption and the significantly lower maintenance costs of LED lights. When applied to an entire city or municipality with many traffic lights, these savings multiply considerably.
