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 1.6 gallons per min = 48

Step 3 find the difference in gallons used

75 - 48 = 27 gallons savings

Step 4 find the cost savings in water

27 x $0.0056 = $0.1512 water savings per day

Step 5 find the number of heated gallons of water

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

48 x 60% = 28.8 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 28.8 gallons to heat = 23,304.3667 BTUs per day

Step 10 convert BTUs to therms

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

23,304.3667 / 100,000 = 0.233 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

0.233 therms per day x 29.3071 KWh per therm = 6.8286 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

6.8286 daily KWh use * $0.118 cost per KWh = $0.8058 per day cost

Step 13 find the difference in electric savings

$1.2591 - $0.8058 = $0.4533 electric savings per day

Step 14 add the water and electric savings

$0.4533 daily electric savings + $0.1512 daily water savings = $0.6045 daily savings

Step 15 find yearly and lifetime savings in dollars with electric

$0.6045 x 365 = $220.64 yearly savings with electric

$220.64 x 15 year estimated life = $3,309.64 estimated lifetime savings with electric

Step 16 find yearly and lifetime electric savings

10.6707 - 6.8286 = 3.8421 daily KWh savings

3.8421 x 365 = 1,402.4 yearly KWh savings

1,402.4 x 15 year estimated life = 21,035 lifetime KWh savings

Step 17 find yearly and lifetime water savings

27 gallons daily water savings x 365 = 9,855 gallons yearly water savings

9,855 x 15 year estimated life = 147,825 lifetime water savings

$0.1512 daily water savings x 365 days = $55.19 yearly water savings