Family Chart for Setting Water Heater Timer/ Based on temperature of water
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Meter on water heater
The Kwh meter is din rail mounted inside enclosure.
Records billable power usage in Kwh. Multiply by rate you pay per Kwh to get monthly/ yearly cost of running electric water heater.

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Bomain power meter
240 volt pass through Kwh  meter
2T2502GA beige plastic enclosure
2T2500GA grey plastic enclosure
din rails

Resource:
Enclosures
How to install electric meter on 240Volt water heater
Formula for heating water inside tank:
Gallon Per Hour (Electric) = (KW x 3413) divided by (temp. rise x 8.25) or (KW x 414) divided by (temp rise.)
Let's say you have 5500 watt elements.
let's say incoming water temperature is 65°F and you want to heat tank to 115°, or 40° rise in temperature.

5500 watt or 5.5Kw elements x 3413 = 18771.5
40 degree temperature rise x 8.25 = 330
So in this specific situation, the element would heat 56.88 gallons per hour

If you have 4500 watt elements and incoming water temperature is 55°, and you want to heat to 120°, then the temperature rise is 65°
4.5 KW x 3413 = 15358.5
65 degree temperature rise x 8.25 = 536
So one element would heat 28 gallons per hour

This number is for EACH element, but does NOT consider heat loss from tank, room temperature, or thickness of insulation etc.
Remember, with residential simultaneous tank, only ONE element is ON at one time.
Upper element is ON, or lower element is ON, or BOTH elements are off. At no time are both elements on.
Check label on side of tank for size and element wattage read more
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° 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

54° Approx annual average outdoor temperature for northern US states
See avertage underground water temperature chart
65° Approx annual average outdoor temperature for southern US states
Any underground water pipe is using geothermal heat from ground to assist water heater
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˘
ost 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°/td>     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/td>     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°/td> 120°/td>     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°/td> 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°
d
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 1Hour 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
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
water consumption bathtub
Safety grab bar
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Regular bath uses 13- 15 gallons hot water (20 gal water total)

Set water heater timer for 45-60 minutes for hot bath

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Fully heated 40 gallon tank gives 2 baths and 1 shower
water consumption shower Shower uses 6 - 8 gallons of hot water (10 gal water total)

Set water heater timer for 20-30 minutes for hot shower

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hot water consumption
Clean shower and doors with White vinegar
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See example chart
Old sizing chart
Post 2015 heaters require high tech for sizes over 50 gallon
Take showers instead of bath. Save 10 gallons hot water each time.
To achieve same hot water consumption as previous heater withut buying more expensive heater install 2 water heaters, cut consumption, maintain heater, turn up thermostat temperature

Two water heaters
9 ways to save with water heater
Maintain water heater
How to adjust themostat
Ways to increase hot water
Calculate first hour delivery


For large bathtub, use 80 gallon first hour

What size water heater?

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.

What size water heater for oversize bathtub?

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
safety chart

How to adjust temperature on water heaters
How to install gas water heater

Troubleshoot gas water heater

Troubleshoot electric 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
Read sediment; sediment removal; softened water
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Icon gas valve

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