Step 1 find cost per gallon

$2.80 fresh water + $2.80 waste water = $5.60 per 1000 gallons

$5.60 / 1000 = $0.0056 per gallon

Step 2 find daily gallon usage

30 mins x 2.5 gallons per min = 75

30 mins x 2 gallons per min = 60

Step 3 find the difference in gallons used

75 - 60 = 15 gallons savings

Step 4 find the cost savings in water

15 x $0.0056 = $0.0840 water savings per day

Step 5 find the number of heated gallons of water

75 x 60% = 45 gallons of heated water per day

60 x 60% = 36 gallons of heated water per day

Step 6 find the number of degrees of heating water

140 water heater temp - 57.5 cold water temp = 82.5 degrees

Step 7 multiply the number of degrees by the 8.337 BTUs it takes to heat one gallon of water one degree

8.337 BTUs x 82.5 degrees to raise by = 687.8025 BTUs to heat 1 gallon to desired temp

Step 8 take into account the hot water heater efficiency

687.8025 BTUs / 85% = 809.1794

Step 9 multiply your efficiency adjusted BTUs by the number of gallons to be heated

809.1794 BTUs x 45 gallons to heat = 36,413.0730 BTUs per day

809.1794 BTUs x 36 gallons to heat = 29,130.4584 BTUs per day

Step 10 convert BTUs to therms

36,413.0730 / 100,000 = 0.3641 therms per day

29,130.4584 / 100,000 = 0.2913 therms per day

Step 11 covert therms to kilowatt hours for electric water heaters

0.3641 therms per day x 29.3071 KWh per therm = 10.6707 KWh per day

0.2913 therms per day x 29.3071 KWh per therm = 8.5372 KWh per day

Step 12 find the cost of heating water with electric

10.6707 daily KWh use * $0.118 cost per KWh = $1.2591 per day cost

8.5372 daily KWh use * $0.118 cost per KWh = $1.0074 per day cost

Step 13 find the difference in electric savings

$1.2591 - $1.0074 = $0.2517 electric savings per day

Step 14 add the water and electric savings

$0.2517 daily electric savings + $0.0840 daily water savings = $0.3357 daily savings

Step 15 find yearly and lifetime savings in dollars with electric

$0.3357 x 365 = $122.53 yearly savings with electric

$122.53 x 15 year estimated life = $1,837.96 estimated lifetime savings with electric

Step 16 find yearly and lifetime electric savings

10.6707 - 8.5372 = 2.1335 daily KWh savings

2.1335 x 365 = 778.7 yearly KWh savings

778.7 x 15 year estimated life = 11,681 lifetime KWh savings

Step 17 find yearly and lifetime water savings

15 gallons daily water savings x 365 = 5,475 gallons yearly water savings

5,475 x 15 year estimated life = 82,125 lifetime water savings

$0.0840 daily water savings x 365 days = $30.66 yearly water savings