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

13.2 mins x 2.5 gallons per min = 33

13.2 mins x 0.5 gallons per min = 6.6

Step 3 find the difference in gallons used

33 - 6.6 = 26.4 gallons savings

Step 4 find the cost savings in water

26.4 x $0.0056 = $0.1478 water savings per day

Step 5 find the number of heated gallons of water

33 x 20% = 6.6 gallons of heated water per day

6.6 x 20% = 1.32 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 6.6 gallons to heat = 5,340.5840 BTUs per day

809.1794 BTUs x 1.32 gallons to heat = 1,068.1168 BTUs per day

Step 10 convert BTUs to therms

5,340.5840 / 100,000 = 0.0534 therms per day

1,068.1168 / 100,000 = 0.0107 therms per day

Step 11 covert therms to kilowatt hours for electric water heaters

0.0534 therms per day x 29.3071 KWh per therm = 1.565 KWh per day

0.0107 therms per day x 29.3071 KWh per therm = 0.3136 KWh per day

Step 12 find the cost of heating water with electric

1.565 daily KWh use * $0.118 cost per KWh = $0.1847 per day cost

0.3136 daily KWh use * $0.118 cost per KWh = $0.0370 per day cost

Step 13 find the difference in electric savings

$0.1847 - $0.0370 = $0.1477 electric savings per day

Step 14 add the water and electric savings

$0.1477 daily electric savings + $0.1478 daily water savings = $0.2955 daily savings

Step 15 find yearly and lifetime savings in dollars with electric

$0.2955 x 365 = $107.87 yearly savings with electric

$107.87 x 3 year estimated life = $323.62 estimated lifetime savings with electric

Step 16 find yearly and lifetime electric savings

1.565 - 0.3136 = 1.2514 daily KWh savings

1.2514 x 365 = 456.8 yearly KWh savings

456.8 x 3 year estimated life = 1,370 lifetime KWh savings

Step 17 find yearly and lifetime water savings

26.4 gallons daily water savings x 365 = 9,636 gallons yearly water savings

9,636 x 3 year estimated life = 28,908 lifetime water savings

$0.1478 daily water savings x 365 days = $53.96 yearly water savings