How much does it cost to leave a light on for a week?

The cost of leaving a light on for a week depends on several factors, including the wattage of the bulb, the type of light bulb you are using, and the electricity rate in your area (usually measured in kilowatt-hours, or kWh). Let’s break it down based on different types of light bulbs, so you can get a better idea of the cost.

1. Incandescent Bulbs

Incandescent bulbs are the least energy-efficient, so they consume more electricity.

• Wattage: 60W (0.06 kW)
• Hours per day: 24 hours (assuming the light is left on all day, every day for a week)
• Electricity cost: $0.12 per kWh (average US rate)

Calculation for a 60W Incandescent Bulb:

• Power consumed per day: 0.06 kW × 24 hours = 1.44 kWh
• Power consumed per week: 1.44 kWh × 7 days = 10.08 kWh
• Cost per week: 10.08 kWh × $0.12 = $1.21

Result: Leaving a 60W incandescent bulb on for a week will cost about $1.21.

2. Compact Fluorescent Lamps (CFLs)

CFLs are much more efficient than incandescent bulbs, but still consume more energy than LEDs.

• Wattage: 14W (0.014 kW)
• Hours per day: 24 hours
• Electricity cost: $0.12 per kWh

Calculation for a 14W CFL:

• Power consumed per day: 0.014 kW × 24 hours = 0.336 kWh
• Power consumed per week: 0.336 kWh × 7 days = 2.35 kWh
• Cost per week: 2.35 kWh × $0.12 = $0.28

Result: Leaving a 14W CFL on for a week will cost about $0.28.

3. LED Bulbs

LED bulbs are the most energy-efficient option and consume the least electricity.

• Wattage: 9W (0.009 kW)
• Hours per day: 24 hours
• Electricity cost: $0.12 per kWh

Calculation for a 9W LED Bulb:

• Power consumed per day: 0.009 kW × 24 hours = 0.216 kWh
• Power consumed per week: 0.216 kWh × 7 days = 1.51 kWh
• Cost per week: 1.51 kWh × $0.12 = $0.18

Result: Leaving a 9W LED bulb on for a week will cost about $0.18.

Summary of Weekly Costs

Factors to Consider:

1. Wattage: The higher the wattage, the more energy the bulb consumes, and the higher the cost.
2. Electricity Rate: The cost of electricity varies by location. For example, in some places, electricity might cost $0.10 per kWh, while in others it could be as high as $0.30 per kWh.
3. Hours of Use: If you leave the light on for fewer than 24 hours, the cost will be lower. For instance, a 9W LED bulb used for 4 hours a day for a week will cost significantly less than leaving it on 24/7.

Conclusion:

As you can see, the cost to leave a light on for a week is relatively low, but using energy-efficient options like LED bulbs can help you save money in the long term. Switching to LED bulbs can also reduce your overall energy consumption, benefiting both your wallet and the environment.