How
to figure Volts-Amps-Watts for residential water
heater
Take photo of label for records.
Water heaters with 2 elements are 240Volt
Helpful links:
Water heater manufacturers
Find age of water heater using serial number on label
 Typical electric water heater label See larger image |
Look
for Volts and Watts on label: 1 Phase or single-phase is household electric service 240 Volts Two 5500 Watt elements Total connected 5500 watts |
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Total
Watt rating for tank shows on label: 5500 Watts If water heater has 2 elements and both elements are 5500, then overall tank Wattage is 5500 Both elements are never turned on at same time How electric water heater works Label shows this water heater is non-simultaneous. Non-simultaneous means that both elements are not ON at same time. One element is ON or other element is ON, or both are OFF. If water heater is simultaneous, both elements could be ON at same time and watt rating for tank would be 5500 watts x 2 = 11,000 watts How to wire water heater thermostats |
Formulas:
Volt x Amp = Watt
Amp = Watt ÷ Volt
More Electrical formulasLabel gives Volts and Watts
Volts x Amps = Watts --Same as-- Amps = Watts ÷ Volts
Use formula:
5500 Watt element ÷ 240 Volts = 22.91 Amps or 23 Amps
Other examples
4500 Watt element ÷ 240 Volts = 18.75 Amps
3500 Watt element ÷ 240 Volts = 14.5 Amps
1500 Watt element ÷ 240 Volts = 6.25 Amps
40 Watt light bulb ÷ 120 Volts = 0.33 Amps
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When replacing elements, use same Wattage shown on tank label
Any generic element will work as replacement
If using smaller wattage, tank will heat slower.
How to replace element
How to test element
Think about the difference between 40 Watt and 100 Watt light bulb.
Higher the Watts, the hotter the light bulb, and the higher output of total energy
So 5500 Watt element gets hotter than 3500 Watt element, and 5500 Watt uses more total energy
Why are elements different Wattage?
Think about a light bulb. A closet can be lit with one 40 Watt bulb. But a large room requires more Wattage.
So very large water heaters use 5500 Watt element since they heat more water.
Most residential tanks have 4500 Watt elements
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How to wire thermostats and elements
How to troubleshoot electric water heater
Ready for peak electric prices?
How-to-wire-water-heater-with-switches-and-timers
How to wire off-peak water heater thermostats
 Larger image | Check label on side of tank for volts and watts Every appliance, switch, outlet and bulb has a label Residential water heaters with 2 elements are 240Volts Residential water heaters are non-simultaneous This means both elements are never ON at same time. Element wattage is tank wattage If tank has 4500 watt elements, then tank wattage is 4500W Recommend 30 amp breaker and 10 gauge wire for all 240Volt water heaters How to wire water heaters How to wire off-peak water heater |
 | Household water heaters are wired for NON-simultaneous operation. Both elements are not ON at same time How to wire water heater thermostats How water heaters work How to wire off-peak water heater |
Use 30 amp breaker and 10 gauge wire on household water heater.
Circuit runs cooler = less amp loss from heat = more efficient use of electricity
Circuit breaker and breaker box last longer
How to replace circuit breaker
9-ways to save with water heater
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Basic
240Volt water heater circuit Example shows water heater on dedicated 240Volt breaker. Dedicated means the breaker does not supply power to other circuits. Another example: Microwave oven is normally on dedicated 120Volt breaker How to replace circuit breaker How to install subpanel Troubleshoot electric water heater |
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How to install electric meter on water heater |
Orange-colored 10 gauge wire for 30 Amp breakers
30 Amp breaker x 240Volts = 7200 watts => 80% rule applies: 7200 Watts x 80% = 5760 Watts safe maximum
80% rules applies to household electrical loads
Other ratings:
Yellow-colored 12 ga wire for 20 Amp breakers
White-colored 14 ga wire for 15 Amp breakers
18 ga lamp cord or 1 residential can opener, pencil sharpener, floor lamp etc
What size circuit breaker? 30 Amp
For safety > a circuit breaker is allowed to handle 80% of Amps shown
30 Amp breaker x 80% rule = 24 Amps safe maximum
Calculation above shows that 5500 Watt water heater uses 23 Amps
And 30 Amp circuit breaker can carry 24 Amps
So a 30 Amp circuit breaker can safely handle the 23 Amps needed for 5500 Watt water heater
Oversized breaker and wire run cooler and save money, but make sure breaker size and wire size match
How much does it cost to operate gas and electric water heaters
Avg state price chart in pdf
How much does it cost to run Electric water heater:
3 hours is approximate daily run-time for a water heater [depending on usage and temperature of incoming water]
Bath uses 12-15 Gallons hot water <> shower uses 5-9 Gallons hot water > Hot water use chart
5500 Watts x 3 hours = 16,500 watt-hours or 16.5 Kwh per day
For a full 30-day month <=> 30 days x 16.5 Kwh per day = 495 Kwh per month for water heater electricity
Calculate cost <=> 495 Kwh x $.10 per Kwh = $49.50 + tax
As general rule, electric water heaters operate at 99% efficiency with or without water-softener > until sediment reaches bottom element > full efficiency is restored when sediment removed How to remove sediment Read research pdf
5500 Watt tank = 495 Kwh per month = $49.50 per month + tax
4500 Watt tank = 405 Kwh per month = $40.50 per month
3500 Watt tank = 315 Kwh per month = $31.50 per month assuming low usage
1500 Watt tank = 135 Kwh per month = $13.50 per month
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3
hours a day @ $.12 per Kwh 5500 Watt tank = $59.40 per month + tax 4500 Watt tank = $48.60 per month 3500 Watt tank = $37.80 per month 1500 Watt tank = $16.20 per month |
3
hours a day @ $.14 per Kwh 5500 Watt tank = $69.30 per month + tax 4500 Watt tank = $56.70 per month 3500 Watt tank = $44.10 per month 1500 Watt tank = $18.90 per month |
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3
hours a day @ $.16 per Kwh 5500 Watt tank = $79.20 per month + tax 4500 Watt tank = $64.80 per month 3500 Watt tank = $50.40 per month 1500 Watt tank = $21.60 per month |
3
hours a day @ $.20 per Kwh 5500 Watt tank = $99.00 per month + tax 4500 Watt tank = $81.00 per month 3500 Watt tank = $63.00 per month 1500 Watt tank = $27.00 per month |
| Chart above in pdf |
Read 9 ways to save with a water heater
Compare 13 electric water heater timers
Electric water heaters operate at 99% efficiency with or without water softener Read
Tempering tank passively pre-heats cold water
Incoming water to household is geothermally heated since pipes are underground
Add a tempering tank to preheat very cold incoming water
9 ways to save with water heater
Wall timers are usually 15 Amps [unless rated for heavy duty]
Ordinary household light switch is usually 15 Amps
Lowes carries Cooper-brand green-color 30 Amp switch
Again the 80% safety rule applies, so .80 x 15 Amp = 12 amps maximum for a 15 amp switch or timer
When wired to a water heater contactor, ordinary switches can control a water heater
120Volt Outlets have wide and narrow blades: Narrow blade is Hot and wide blade is neutral
Most household switches and outlets are rated 15Amp
How to wire outlet combo
15Amp switch is rated for 1440 Watt
14 - 100Watt light bulbs = 1400Watts
15 Amp switch x .80 = 12 Amps
12 Amps x 120 Volts = 1440 Watts, therefore *14* 100-Watt light bulbs can be put on a single 15 Amp switch
Ordinary house switch can safely control several light bulbs + a desk lamp + a ceiling fan + etc. up to 1400 Watts
Add up Watts of each item to calculate the total load on the switch.
Same facts hold true for wall plugs which are usually rated 15 Amps and can carry 1400 Watts.
You can see that 1500 Watt microwaves and 1500 Watt space heaters should connect to heavy wires and switches Electricity from power pole to breaker box
All single phase circuits require 2 wires to complete the circuit
120Volt take 1 hot wire and 1 neutral wire
240Volt takes 2 hot wires
No neutral wire is needed to complete 240Volt circuit
240 Volts can deliver energy more efficiently than 120 Volts
240 Volt appliances are more efficient
See basic 120 & 240 water heater circuit
Amps is a measure of the size roadway needed to supply energy to appliance
For example, a 5500 Watt element needs more roadway than a 40 Watt light bulb
Roadway is made up of circuit breaker, wire, and electrical connectors needed to handle the energy
See inside main breaker box
Kwh is the standard unit for billing used by electric company <=> the cost varies from 10¢ - 20¢ per Kwh
1 Kwh = 1000 watt-hours of electricity Average electric price by state
40 Watt light bulb turned on for 10 hours <=> 40 Watts x 10 hours = 400 watt-hours or .4 Kwh
To calculate cost, multiply Kwh x price <=>
For example .4 Kwh x $.10 per Kwh = .04 or just 4¢ for each 10 hours of 60 Watt light
Small Refrigerator: $60 per year
Big refrigerator: $300 per year
| Small
786 watt Refrigerator rated 6.5 Amp/ full load
115 Volt 1.6 Kwh per day = 600 Kwh per year. @$.10 per Kwh = $60 per year @$.12 per Kwh = $72 per year |
 Use Kill A Watt meter to measure 120Volt electric usage Instruction .pdf |
Big Screen TV: $70-140 per year
Satellite receiver: $18 per year
TV: 300-500 Watts + 3 watt standby
$.10 per Kwh
6 hours TV per day = $70-140 per year
For example double-oven has a Watt rating of 7.0 KW - that means 7000 Watts
The top oven uses 1/2 total wattage or 3500 watts or 3.5 KW >> the bottom oven uses 1/2 or 3.5 KW
For every hour the top oven is 'on' uses up to 3.5 Kwh of power
When both top and bottom ovens are 'on' for one hour, the appliance uses up to 7.0 Kwh
When buying appliance:
Look at wattage printed on label. Take photo of label with phone. Compare wattage with old appliance. It requires same energy to heat water and heat homes and cook food as before. A giant appliance does not lower bills. Energy Star rating does NOT mean new appliance will pay for itself. With Energy Star, expect $2-6 per year on same size appliance. Appliances give off warm air that works against AC in summer, but helps heater in winter. Reducing consumption and buying smaller wattage appliance is best way to lower energy bill.
Put your TV and satellite box and computer on a power strip/ turn off power strip when not in use
Look at power strips that have timers.
Put bath fan, garage light and whole house fan on a countdown timer.
Read more about standby power loss Read1 Read2
Remember, when everybody conserves electricity, the price remains low and fewer resources are used
How to set temperature and common gas control error codes
Troubleshoot gas water heater
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Troubleshoot Tankless water heater
How to read the gas meter
Water heater Box timers
Water heater timers
