I only need help with part B.
A 250W computer power
supply is on 10 h per day.
Part A
If the cost of electricity is $0.15/kWh, what is the energy cost (to the nearest dollar) if this computer is used like this for a year (365 days)?
140 dollars
Part B
If this power supply is replaced by a more efficient 100-W version and it costs $100, how long will it take the decreased operating cost to pay for this power supply? (in years)
A. 0.250kW * 10h/day * 365days/yr. =
912.5 kWh./yr
Cost = 912.5kWh/yr * $0.15/kWh=$137/yr.
B. (0.100/0.250) * 912.5kWh/yr=365kWh/yr
Cost = 365kWh/yr * $0.15/kWh = $55/yr
Savings = 137 - 55 = $82/yr
$100/$82 = 1.22 Years.
To calculate how long it will take for the decreased operating cost to pay for the new power supply, there are a few steps you can follow:
Step 1: Calculate the energy consumption of the original power supply.
The original power supply has a power rating of 250W and is used for 10 hours per day. To calculate the energy consumption per day, you can multiply the power rating by the usage time:
Energy consumption per day = 250W * 10 hours = 2500 Wh = 2.5 kWh
Step 2: Calculate the energy consumption per year.
Since there are 365 days in a year, you can multiply the energy consumption per day by 365:
Energy consumption per year = 2.5 kWh * 365 = 912.5 kWh
Step 3: Calculate the energy cost per year for the original power supply.
The cost of electricity is given as $0.15 per kWh. To find the energy cost for the year, you can multiply the energy consumption per year by the cost per kWh:
Energy cost per year = 912.5 kWh * $0.15/kWh = $136.875
Since we are rounding to the nearest dollar, the energy cost for the original power supply is $137.
Step 4: Calculate the energy cost per year for the new power supply.
The new power supply has a power rating of 100W. Using the same steps as before, you can calculate the energy consumption per year for the new power supply:
Energy consumption per year = 100W * 10 hours * 365 days = 365,000 Wh = 365 kWh
Energy cost per year for the new power supply = 365 kWh * $0.15/kWh = $54.75
Step 5: Calculate the savings per year.
To find the savings per year, subtract the energy cost per year for the new power supply from the energy cost per year for the original power supply:
Savings per year = $137 - $54.75 = $82.25
Step 6: Calculate the payback period.
Finally, to calculate the payback period, divide the cost of the new power supply ($100) by the annual savings:
Payback period = $100 / $82.25 ≈ 1.22 years
Therefore, it will take approximately 1.22 years for the decreased operating cost to pay for the new power supply.