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 1.6 gallons per min = 48 |
Step 3 find the difference in gallons used75 - 48 = 27 gallons savings |
Step 4 find the cost savings in water27 x £0.0109 = £0.2943 water savings per day |
Step 5 find the number of heated gallons of water75 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 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 28.8 gallons to heat = 23,304.3667 BTUs per day |
Step 10 convert BTUs to therms36,413.0730 / 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 heaters0.3641 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 electric10.6707 daily KWh use * £0.140 cost per KWh = £1.4939 per day cost 6.8286 daily KWh use * £0.140 cost per KWh = £0.9560 per day cost |
Step 13 find the difference in electric savings£1.4939 - £0.9560 = £0.5379 electric savings per day |
Step 14 add the water and electric savings£0.5379 daily electric savings + £0.2943 daily water savings = £0.8322 daily savings |
Step 15 find yearly and lifetime savings in dollars with electric£0.8322 x 365 = £303.75 yearly savings with electric £303.75 x 15 year estimated life = £4,556.30 estimated lifetime savings with electric |
Step 16 find yearly and lifetime electric savings10.6707 - 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 savings27 gallons daily water savings x 365 = 9,855 gallons yearly water savings 9,855 x 15 year estimated life = 147,825 lifetime water savings £0.2943 daily water savings x 365 days = £107.42 yearly water savings |