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 1.5 gallons per min = 45

Step 3 find the difference in gallons used

75 - 45 = 30 gallons savings

Step 4 find the cost savings in water

30 x $0.0056 = $0.1680 water savings per day

Step 5 find the number of heated gallons of water

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

45 x 60% = 27 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 27 gallons to heat = 21,847.8438 BTUs per day

Step 10 convert BTUs to therms

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

21,847.8438 / 100,000 = 0.2185 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

0.2185 therms per day x 29.3071 KWh per therm = 6.4036 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

6.4036 daily KWh use * $0.118 cost per KWh = $0.7556 per day cost

Step 13 find the difference in electric savings

$1.2591 - $0.7556 = $0.5035 electric savings per day

Step 14 add the water and electric savings

$0.5035 daily electric savings + $0.1680 daily water savings = $0.6715 daily savings

Step 15 find yearly and lifetime savings in dollars with electric

$0.6715 x 365 = $245.10 yearly savings with electric

$245.10 x 15 year estimated life = $3,676.46 estimated lifetime savings with electric

Step 16 find yearly and lifetime electric savings

10.6707 - 6.4036 = 4.2671 daily KWh savings

4.2671 x 365 = 1,557.5 yearly KWh savings

1,557.5 x 15 year estimated life = 23,362 lifetime KWh savings

Step 17 find yearly and lifetime water savings

30 gallons daily water savings x 365 = 10,950 gallons yearly water savings

10,950 x 15 year estimated life = 164,250 lifetime water savings

$0.1680 daily water savings x 365 days = $61.32 yearly water savings