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 1.75 gallons per min = 52.5

Step 3 find the difference in gallons used

75 - 52.5 = 22.5 gallons savings

Step 4 find the cost savings in water

22.5 x $0.0056 = $0.1260 water savings per day

Step 5 find the number of heated gallons of water

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

52.5 x 60% = 31.5 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 31.5 gallons to heat = 25,489.1511 BTUs per day

Step 10 convert BTUs to therms

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

25,489.1511 / 100,000 = 0.2549 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

0.2549 therms per day x 29.3071 KWh per therm = 7.4704 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

7.4704 daily KWh use * $0.118 cost per KWh = $0.8815 per day cost

Step 13 find the difference in electric savings

$1.2591 - $0.8815 = $0.3776 electric savings per day

Step 14 add the water and electric savings

$0.3776 daily electric savings + $0.1260 daily water savings = $0.5036 daily savings

Step 15 find yearly and lifetime savings in dollars with electric

$0.5036 x 365 = $183.81 yearly savings with electric

$183.81 x 15 year estimated life = $2,757.21 estimated lifetime savings with electric

Step 16 find yearly and lifetime electric savings

10.6707 - 7.4704 = 3.2003 daily KWh savings

3.2003 x 365 = 1,168.1 yearly KWh savings

1,168.1 x 15 year estimated life = 17,522 lifetime KWh savings

Step 17 find yearly and lifetime water savings

22.5 gallons daily water savings x 365 = 8,213 gallons yearly water savings

8,213 x 15 year estimated life = 123,188 lifetime water savings

$0.1260 daily water savings x 365 days = $45.99 yearly water savings