Waterheatertimer.org
is a self-help site		 Compare 16 electric and 2 gas  water heater timers How much water does bath-shower use? See math for heating water with electricity Figure Volts Amps Watts for water heater Do-it-yourself
2012

Family Chart for Setting Water Heater Timer/ Based on temperature of water
Check label on side of tank for size and element wattage read more
Bath uses 13-15 gallons hot water/ Shower 6-8 gallons hot water
.000293
20 gph for 90 degree rise with 4500 watt element.

30 Gallon Water Heater with 3500 Watt Elements

30 x 8.34 pounds per gallon = 250.2 pounds of water <> it takes .000293 Kwh to raise 1 pound of water 1° F (assuming ideal conditions inside tank*)
250.2 x .000293 x rise in temperature = Kwh
Temperature
of water at
start time		 Raise temperature to 120°  30 Gallon/ 3500 Watt Water heater > delivers 3.5 Kilowatts per hour..
Kwh needed to make 30 gallons
of 120° hot water		 Set timer to make 30 gallons:
(For gas heater, divide times by half)		 Cost per day at 14¢ per Kwh Cost per
day: @12¢		 Cost per
day: @10¢
32° 120°     6.45 Kwh 1 Hour 50 minutes  .74 per day = $22.09 mo  .77  .64
40° 120°     5.86 Kwh 1 Hour 40 minutes  .67 per day = $20.01 mo  .70  .58
50° 120°     5.13 Kwh 1 Hour 27 minutes  .59 per day = $17.58 mo  .61  .51
60° 120°     4.39 Kwh 1 Hour 15 minutes  .50 per day = $15.07 mo  .53  .44
70° 120°     3.66 Kwh 1 Hour 2 minutes  .42 per day = $12.56 mo  .44  .36
80° 120°     2.93 Kwh 50 minutes  .33 per day = $10.03 mo  .35  .29
90° 120°     2.2 Kwh 37 minutes  .25 per day = $7.52 mo  .26  .22
See chart as image
For gas calculation: it takes about 50,000 BTU to raise temperature of water 70 degrees at a rate of one gallon per minute.
This assumes gas water heater efficiency has not been reduced by sediment build-up. See efficiency illustration

40 Gallon Water Heater with 4500 Watt Elements

40 x 8.34 pounds per gallon =  333.6 pounds of water <> it takes .000293 Kwh to raise 1 pound of water 1° F (assuming ideal conditions inside tank*)
333.6 x .000293 x rise in temperature = Kwh
Temperature
of water at
start time		 Raise temperature to 120°  40 Gallon/ 4500 Watt Water heater > delivers 4.5 Kilowatts per hour..
Kwh needed to make 40 gallons
of 120° hot water		 Set timer to make 40 gallons:
(For gas heater, divide times by half)		 Cost per day at 14¢ per Kwh Cost per
day: @12¢		 Cost per
day: @10¢
32° 120°     8.60 Kwh 1 Hour 54 minutes 1.20 per day = $36.00 mo 1.03  .86
40° 120°     7.82 Kwh 1 Hour 44 minutes  1.09 per day = $32.84 mo  .94  .78
50° 120°     6.84 Kwh 1 Hour 31 minutes  .96 per day = $28.73 mo  .82  .68
60° 120°     5.86 Kwh 1 Hour 18 minutes  .82 per day = $24.61 mo  .70  .58
70° 120°     4.88 Kwh 1 Hour 5 minutes  .68 per day = $20.50 mo  .58  .48
80° 120°     3.91 Kwh 52 minutes  .54 per day = $16.42 mo  .47  .39
90° 120°     2.93 Kwh 39 minutes  .41 per day = $12.31 mo  .35  .29
See chart as image

50 Gallon Water Heater with 4500 Watt Elements

50 x 8.34 pounds per gallon =  417 pounds of water <> it takes .000293 Kwh to raise 1 pound of water 1° F (assuming ideal conditions inside tank*)
417 x .000293 = .122181 x rise in temperature = Kwh
Temperature
of water at
start time		 Raise temperature to 120°  50 Gallon/ 4500 Watt Water heater > delivers 4.5 Kilowatts per hour..
Kwh needed to make 50 gallons
of 120° hot water		 Set timer to make 50 gallons:
(For gas heater, divide times by half)		 Cost per day at 14¢ per Kwh Cost per
day: @12¢		 Cost per
day: @10¢
32° 120°     10.75 Kwh 2 Hour 23 minutes 1.50 per day = $45.00 mo 1.29 1.07
40° 120°     9.77 Kwh 2 Hour 20 minutes  1.37 per day = $41.34 mo  1.17  .98
50° 120°     8.55 Kwh 1 Hour 54 minutes  1.20 per day = $35.91 mo 1.03  .86
60° 120°     7.33 Kwh 1 Hour 37 minutes 1.03 per day = $30.79 mo  .88  .73
70° 120°     6.10 Kwh 1 Hour 21 minutes  .85 per day = $25.62 mo  .73  .61
80° 120°     4.88 Kwh 1 Hour 5 minutes  .68 per day = $20.50 mo  .59  .49
90° 120°     3.66 Kwh 49 minutes  .51 per day = $15.371 mo  .44  .37
See chart as image


50+ Gallon Water Heater with 5500 Watt Elements

50 x 8.34 pounds per gallon =  417 pounds of water <> it takes .000293 Kwh to raise 1 pound of water 1° F (assuming ideal conditions inside tank*)
417 x .000293 x rise in temperature = Kwh
Temperature
of water at
start time		 Raise temperature to 120°  50 Gallon/ 5500 Watt Water heater > delivers 5.5 Kilowatts per hour..
Kwh needed to make 50 gallons
of 120° hot water		 Set timer to make 50 gallons:
(For gas heater, divide times by half)		 Cost per day at 14¢ per Kwh Cost per
day: @12¢		 Cost per
day: @10¢
32° 120°     10.75 Kwh 1 Hour 57 minutes 1.51 per day = $45.15 mo 1.29  1.07
40° 120°     9.77 Kwh 1 Hour 47 minutes 1.36 per day = $41.03 mo 1.17  .98
50° 120°     8.55 Kwh 1 Hour 33 minutes 1.18 per day = $35.91 mo  1.02  .85
60° 120°     7.33 Kwh 1 Hour 20 minutes 1.02 per day = $30.78 mo  .88  .73
70° 120°     6.11 Kwh 1 Hour 6 minutes  .85 per day = $25.66 mo  .73  .61
80° 120°     4.89 Kwh 53 minutes  .68 per day = $20.54 mo  .58  .49
90° 120°     3.66 Kwh 40 minutes  .51 per day = $15.32 mo  .44  .36
See chart as image


54° Approx annual average outdoor temperature for northern US states
65° Approx annual average outdoor temperature for southern US states
See shallow groundwater temperature map
*Ideal tank conditions vary
Read sediment; sediment removal; softened water

How to install electric meter on 240Volt water heater

Two methods:
1) Install electric meter on line going to water heater
2) Install Hour meter on each water heater element

E-mail: info@waterheatertimer.org
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