To calculate how much carbon dioxide (CO₂) emissions are prevented by switching to LEDs, we need to consider the following key factors:
- Energy saved by switching to LEDs (in kilowatt-hours, or kWh).
- CO₂ emissions per kWh based on the energy mix (coal, natural gas, renewables) used to generate electricity. The average CO₂ emissions per kWh varies by region, but a typical value is 0.92 pounds of CO₂ per kWh for the U.S., according to the EPA. This can be converted to 0.42 kilograms of CO₂ per kWh.
Let’s break it down step by step using a single green traffic light as an example, comparing the incandescent and LED bulbs.
1. Energy Consumption of Incandescent vs. LED
Incandescent Green Bulb:
- Power Consumption: 135 watts
- Operating Hours: 24 hours/day, 365 days/year
- Annual Energy Use:
135 watts×24 hours/day×365 days/year=1,182.6 kWh/year135 \, \text{watts} \times 24 \, \text{hours/day} \times 365 \, \text{days/year} = 1,182.6 \, \text{kWh/year}135watts×24hours/day×365days/year=1,182.6kWh/year
LED Green Bulb:
- Power Consumption: 15 watts
- Annual Energy Use:
15 watts×24 hours/day×365 days/year=131.4 kWh/year15 \, \text{watts} \times 24 \, \text{hours/day} \times 365 \, \text{days/year} = 131.4 \, \text{kWh/year}15watts×24hours/day×365days/year=131.4kWh/year
2. Energy Savings
The energy saved by switching from an incandescent bulb to an LED bulb is:1,182.6 kWh/year (incandescent)−131.4 kWh/year (LED)=1,051.2 kWh/year saved1,182.6 \, \text{kWh/year (incandescent)} – 131.4 \, \text{kWh/year (LED)} = 1,051.2 \, \text{kWh/year saved}1,182.6kWh/year (incandescent)−131.4kWh/year (LED)=1,051.2kWh/year saved
3. CO₂ Emissions Prevented
Using the CO₂ emissions factor of 0.42 kilograms of CO₂ per kWh, we can calculate the amount of CO₂ emissions prevented per year by switching to LEDs:1,051.2 kWh/year×0.42 kg CO₂/kWh=441.5 kg CO₂/year (or 441,520 grams/year)1,051.2 \, \text{kWh/year} \times 0.42 \, \text{kg CO₂/kWh} = 441.5 \, \text{kg CO₂/year} \, (\text{or} \, 441,520 \, \text{grams/year})1,051.2kWh/year×0.42kg CO₂/kWh=441.5kg CO₂/year(or441,520grams/year)
This means that 441.5 kilograms (or about 972 pounds) of CO₂ emissions are prevented per year for each green traffic light switched from an incandescent to an LED.
4. CO₂ Emissions Prevented Over the Lifetime of the LED
Since an LED typically lasts 50,000 hours, which is about 5.7 years of continuous operation, the total amount of CO₂ emissions prevented over the LED’s lifespan is:441.5 kg/year×5.7 years=2,516.55 kg CO₂ prevented over the LED’s lifetime441.5 \, \text{kg/year} \times 5.7 \, \text{years} = 2,516.55 \, \text{kg CO₂ prevented over the LED’s lifetime}441.5kg/year×5.7years=2,516.55kg CO₂ prevented over the LED’s lifetime
5. Scaling Up
If you switch multiple traffic lights or other lighting systems to LEDs, the savings scale up proportionally. For example:
- 10 traffic lights: Prevent 25,165.5 kg (25.2 metric tons) of CO₂ over the LED’s lifetime.
- 100 traffic lights: Prevent 251,655 kg (251.7 metric tons) of CO₂ over the LED’s lifetime.
Conclusion:
By switching a single green traffic light from an incandescent bulb to an LED, you can prevent 441.5 kg of CO₂ emissions per year, or about 2,516.55 kg of CO₂ over the LED’s lifetime. These reductions in carbon dioxide emissions help reduce the overall environmental impact, contributing to efforts against climate change and promoting sustainability.
