a) Total cost (per day) ≈ $1.40
b) Total cost (per year) ≈ $510
c) New annual cost = $327
d) The number of years that the water heater pays for itself is; approximately 4 years
<h3>How to calculate Energy Bill?</h3>
Wattage per hour = 4200 Watts per hour
Number of hours per day = 3 hours
Cost per unit = $0.11 per kilowatt-hour
Savings rate = 36%
Cost water heater = $1,100
a) The total wattage is the product of the wattage per hour and the number of hours;
Total wattage (per day) = Wattage per hour × Number of hours
= 4,200 watts per hour × 3 hours
= 12,600 watt-hours
= 12.6 kilowatt-hours
The total cost is then the product of the total wattage and the cost per unit:
Total cost (per day) = Total wattage × Cost per unit
Total cost (per day) = 12.6 kilowatt-hours × $0.11 per kilowatt-hour
Total cost (per day) = $1.386
Total cost (per day) ≈ $1.40
b) The total cost in a year is the product of the total cost in a day and the number of days in a year. There are 365 days in a year (assuming no leap year).
Total cost (per year) = Total cost (per day) × Number of days in a year
Total cost (per year) = $1.40 × 365
Total cost (per year) = $511
Total cost (per year) ≈ $510
c) We are told that this new water heater saves 36% of annual cost. Thus;
Amount saved = 36% * 510 = $183.6
Thus;
New annual cost = $510 - $183 = $327
d) The number of years that the water heater pays for itself is;
1100/327 = 3.36 or approximately 4 years
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