Question

An energy-efficient water heater draws 4 amps in a 220-volt circuit. It costs $75 more that a standard water heater that draws 18 amps in a standard 115-volt circuit. If electricity costs 10 cents per kilowatt-hour, how long would you have to run the efficient water heater to recoup the difference in price? Show your calculations.

Answer 1

The answer to the question above is "630.25 hours" which is the time to recoup the difference in the water heater cost. This problem can be solved using a simple algebra equation which stated as (18*115*0.1/1000)x - (4*220*0.1/1000)x = $75. In this formula, x represents the time to recoup the difference in the water heater cost (Calculation: 0.207x-0.088x=75 --> 0.119x = 75 --> x = 630.25).