Energy Saver Worksheet: Water-Saving Shower Head | |
These devices save water, but most of your savings come from using less hot water. For example, let's say you heat your house and hot water with natural gas and have an annual bill of $1,500 and used 3000 therms (a therm equals 100,000 BTU a measure of heat), so you paid about .50 cents a therm. Enter the length of your average shower (10 min.) and then calculate the amount of water used at 6 gal. a minute. About 40% of this will be hot water, so multiply the 60 gal. times .4 to get the amount of hot water used, or about 36 gal. It takes 8.33 BTU to raise one gallon of water one degree. Your water heater has to raise it 85 degrees from when it enters the house at about 60 degrees to 145 degrees, so it takes about .13 cents to heat and raise 36 gal. to 85 degrees. If you install the water-saving shower head, you will use only 15 gal. of hot water and spend .05 cents to heat it, for a savings of .08 cents a shower. If your family takes 4 showers a day, you can save about a quarter a day, not counting the cost of the water, which can be substantial in some areas. Estimated Savings for Installing a Water-Saving Shower Head Cost of Energy: (1) $ ____________ (from line (4) Cost of Energy) Average Length of Shower (2) _________ Min Water used to take shower: (6 gpm flow rate) 6 x (2) _______ = (3) _________ Gal. Hot water used: (60% hot 40% cold) (3) _______ x .6 = (4) ________ Gal. Cost to heat water: Electric: ((Gallons x 8.33 x 85)/3413) x (1) Cost of KWH (4) ________ x .21 x (1) $ __________ = (5) $ ___________ Oil: (Gallons x 8.33 x 85)/132,000) x Cost of oil (4) ________ x .0053 x (1) $ ________ = (5) $ ___________ Gas: (Gallons x 8.33 x 85)/100,000) x Cost of gas (4) ________ x .0071 x (1) $ _________ = (5) $ ___________ Water used with Water Saving Shower Head: (2.5 gpm flow rate) 2.5 x (2) _______ = (6) _________ Gal. Hot water used: (60% hot 40% cold) (6) _______ x .6 = (7) _________ Gal. Cost to heat water: Electric: (Gallons x 8.33 X 85)/3413) x (1) Cost of KWH (7) ________ x .21 x (1) $ ___________ = (8) $ ___________ Oil: (Gallons x 8.33 x 85)/132,000) x Cost of oil (7) ________ x .0053 x (1) $ __________ = (8) $ ___________ Gas: (Gallons x 8.33 x 85)/100,000) x Cost of gas (7) ________ x .0071 x (1) $ __________ = (8) $ ___________ (8) $ __________ Savings per shower (5)-(8) (9) $ __________ Showers taken a day (10) __________ Daily Savings (9) x (10) (11) $ __________ Water saving (3) - (6) (12) __________ gals Showers taken a day (9) __________ Daily water saving (12) x (9) (13) __________ gals The biggest savings with these devices is lowering the consumption of hot water. Depending the type of energy used to heat the water, the expected savings can be calculated. Here again the local utility bill is the easiest source for the cost of energy. Length of shower: 10 min water used full flow head 10 x 6 gal/mim 60 gal hot water used 60% 60 x .60 36 gal Cost to heat water electric: ((36 x 8.33 x 85)/3413) x .087 $.65 oil: ((36 x 8.33 x 85)/132,000) x 1.04 $.20 gas: (36 x 8.33 x 85)/100,000) x .5 $.13 WATER USED RESTRICTED FLOW HEAD 10 x 2.5 gal/mim 25 gal hot water used 60% 25 x .60 15 gal cost to heat water electric: (15 x 8.33 x 85)/3413 x .087 $.27 oil (15 x 8.33 x 85)/132,000 x 1.04 $.09 gas (15 x 8.33 x 85)/100,000 x .5 $.05 SAVINGS PER SHOWER: Total Water 35 gal Hot Water 21 gal Dollar savings electric $.38 oil $.11 gas $.08 Showers per day: 4 Total Water Savings: 140 gal Total Dollar saving (electric) $1.52 Assumptions: 10-minute shower uses 50 gallons of water or 5 gal/min. Water-saving shower head will uses 2.5 gal/min. Shower water is 60/40 mix of hot and cold water. 8.33 energy needed to raise one gal 1 degree The water has to be raised 85 degrees in the water tank from 60 degrees to 145 degrees. Formulas: electric use (gallons of water x 8.33 x change in water temperature)/3413 = KWH oil use (gallons of water x 8.33 x change in water temperature)/132,000 = gallons natural gas (gallons of water x 8.33 x change in water temperature)/100,000 = Therms Written by the editors of HouseNet. Copyright HouseNet, Inc. |