What is the cost of lighting a 500-watt outdoor light for 8 hours, if electricity costs 7.5 cents per kilowatt-hour?
The Correct Answer and Explanation is:
To determine the cost of running a 500-watt outdoor light for 8 hours at an electricity rate of 7.5 cents per kilowatt-hour (kWh), we need to follow a few steps.
Step 1: Convert Watts to Kilowatts
Electricity costs are typically calculated in kilowatt-hours (kWh), so we need to convert watts to kilowatts.
- 500 watts is equivalent to 0.5 kilowatts (500 watts ÷ 1,000 = 0.5 kW).
Step 2: Calculate Energy Consumption in kWh
Next, we calculate how much energy the light uses over 8 hours:
- Energy (kWh) = Power (kW) × Time (hours)
- Energy = 0.5 kW × 8 hours = 4 kWh
Step 3: Calculate the Cost
With the energy consumption calculated, we can determine the cost by multiplying the energy used by the rate per kilowatt-hour:
- Cost = Energy (kWh) × Rate (cents per kWh)
- Cost = 4 kWh × 7.5 cents = 30 cents
Final Answer:
The cost of lighting a 500-watt outdoor light for 8 hours at 7.5 cents per kWh is 30 cents.
Explanation:
The calculation method above is useful because electricity providers bill based on energy consumption in kilowatt-hours (kWh). By converting the light’s power from watts to kilowatts, we align it with the billing unit. Multiplying the kilowatts by hours used provides total energy in kWh, representing actual electricity used. Multiplying by the cost per kWh then gives the total cost for the electricity used by the light. This method can be applied to any electrical device to determine its running cost over a period of time, making it a practical tool for budgeting and energy management.