showerhead savings calculations
Step 1 find cost per gallon£5.47 fresh water + £5.46 waste water = £10.93 per 1000 gallons £10.93 / 1000 = £0.0109 per gallon |
Step 2 find daily gallon usage30 mins x 2.5 gallons per min = 75 30 mins x 2.37 gallons per min = 71.1 |
Step 3 find the difference in gallons used75 - 71.1 = 3.89999999999999 gallons savings |
Step 4 find the cost savings in water3.89999999999999 x £0.0109 = £0.0425 water savings per day |
Step 5 find the number of heated gallons of water75 x 60% = 45 gallons of heated water per day 71.1 x 60% = 42.66 gallons of heated water per day |
Step 6 find the number of degrees of heating water140 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 degree8.337 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 efficiency687.8025 BTUs / 85% = 809.1794 |
Step 9 multiply your efficiency adjusted BTUs by the number of gallons to be heated809.1794 BTUs x 45 gallons to heat = 36,413.0730 BTUs per day 809.1794 BTUs x 42.66 gallons to heat = 34,519.5932 BTUs per day |
Step 10 convert BTUs to therms36,413.0730 / 100,000 = 0.3641 therms per day 34,519.5932 / 100,000 = 0.3452 therms per day |
Step 11 covert therms to kilowatt hours for electric water heaters0.3641 therms per day x 29.3071 KWh per therm = 10.6707 KWh per day 0.3452 therms per day x 29.3071 KWh per therm = 10.1168 KWh per day |
Step 12 find the cost of heating water with electric10.6707 daily KWh use * £0.140 cost per KWh = £1.4939 per day cost 10.1168 daily KWh use * £0.140 cost per KWh = £1.4164 per day cost |
Step 13 find the difference in electric savings£1.4939 - £1.4164 = £0.0775 electric savings per day |
Step 14 add the water and electric savings£0.0775 daily electric savings + £0.0425 daily water savings = £0.1200 daily savings |
Step 15 find yearly and lifetime savings in dollars with electric£0.1200 x 365 = £43.80 yearly savings with electric £43.80 x 15 year estimated life = £657.05 estimated lifetime savings with electric |
Step 16 find yearly and lifetime electric savings10.6707 - 10.1168 = 0.5539 daily KWh savings 0.5539 x 365 = 202.2 yearly KWh savings 202.2 x 15 year estimated life = 3,033 lifetime KWh savings |
Step 17 find yearly and lifetime water savings3.89999999999999 gallons daily water savings x 365 = 1,424 gallons yearly water savings 1,424 x 15 year estimated life = 21,353 lifetime water savings £0.0425 daily water savings x 365 days = £15.52 yearly water savings |