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 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


See example chart
Select size of water heater

Household usage

Storage water heater holds 30 / 40 / 50 / 60 / 80 gallons of hot water. Check label on side of tank
hot water consumption


For large bathtub, use 80 gallon first hour
Size chart shows First Hour delivery rating
First hour is capacity of tank at peak-usage times.
For example at night when everybody is taking a shower or bath

Increase amount of hot water with changes and maintenance
How to adjust temperature
How to increase amount of hot water
How to maintain water heater

Homes with garden tub, whirlpool bath, or oversized tub = first hour 80 gallon

Avoid oversized bathtubs.
It's not cheap to heat all that hot water.
Buy a spa.
Drive to ocean and support tourism.
Large bathtub / whirlpool tub

Recommend 80 gallon first hour delivery
Electric: minimum 60-to-80 gallon size just for that one tub
Gas: minimum 50 gallon size just for that one tub

Electric heat pump water heaters generally cannot produce enough hot water.

Tankless promise unlimited hot water, but temperature of water is 120 F and water in tub may be cool by time tub fills. Cost of maintenance and repairs never pay back. All costs are energy.
Troubleshoot Rheem tankless

Turn up thermostat on any water heater to increase amount of available hot water
How to adjust temperature
How to increase amount of hot water
Cost to run water heater

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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