What Size Wire For The Electric Water Heater

What Size Wire For The Electric Water Heater

When you take a warm shower, do you ever enjoy the sensation of the warm water removing your day’s fatigue? Often, the source of that invigorating flow is an electric water heater silently whirring away in one part of your house. However, have you ever thought about the unsung hero that enables this convenience—the wire? What is the size of the electric water heater’s wire? Most 4500-watt Electric Water Heaters are designed to run on 30 amps or 10 gauge cable.

Factors Influencing The Size Of An Electric Water Heater’s Wire

Water Heater Capacity

Your water heater must be considered when choosing the appropriate wire size. The larger the water heater, the larger the wire size needed to transport the electric current securely.

Electrical loads: Intermittent loads draw different amounts of current over time, while continuous loads draw a constant quantity.

Standards and Codes for Electricity

Respecting electrical laws and standards is essential when choosing the wire size for your water heater. Guidelines for wire size are provided by the National Electric Code (NEC) and are dependent on the water heater’s amperage usage.

Distance of Wire Run

The length of the cable that connects the circuit breaker to the water heater is an additional crucial consideration. Extended wire lines may result in voltage dips, which lower the efficiency of water heaters.

The Temperature Outside

The surrounding air temperature in the space where the water heater is situated may also impact the necessary wire size. A higher temperature may cause the wire to overheat and become dangerous.


The majority of water heaters run on 220-250V. It makes use of a double-circuit breaker. You don’t need to worry about voltage as much as amperage because most electric water heaters have similar voltage requirements.


The water heater’s wattage tells you how much electricity it uses. Nevertheless, a water heater’s wattage cannot determine wire size. Amperage is necessary.

Breaker Specifications

Theoretically, you don’t know the breaker size needed to determine the water heater wire size.

After figuring out your circuit’s voltage and the heater’s wattage, you may compute the amperage, which indicates the wire size. Nonetheless, the breaker’s dimensions hold similar significance.

First, it is inconvenient if a water heater is connected to a smaller breaker since the breaker keeps tripping. A too-large breaker will prevent the detection of overloads and short circuits. The size of the breaker is important.

Second, the wiring needs of the water heater will probably be satisfied by matching the size of the breaker. To comply with NEC rules, double the amp rating (25A) of your water heater by 125 percent, using the example from above.


If you’ve ever shopped for a water heater, you know that the tank’s size influences the water heater’s cost. You’re also aware that many contractors measure wire size in gallons.

Water Heater Wire Size Chart

Water Heater Size (gallons)

Wire Size 9(AWG)


14 Gauge Wire


14 Gauge Wire


14 Gauge Wire


The heaters used in the smaller 10- and 20-gallon heaters are less than 2000W. The most popular kind of tiny water heater is a 13.4500-watt, 1600-watt, 120V heater. Since 16 AWG wire can take 14 amps, it is sufficient for these heaters instead of 14 AWG wire. Use the 16 AWG if you’re unsure; it might seem excessive, but it’s the safest option.

Larger water heaters like the 90- and 100-gallon models need stronger heaters. While some conventional 4500-watt heaters are still functional, it is not unusual to have a 10,000-watt water heater powering a 100-gallon water heater (240V circuit). According to the AWG wire capacity chart, an 8 AWG wire size is required because this heater consumes 41.7 amps (with 50A ampacity).

What Wire Gauge Is Required For A 40 Gallon Electric Water Heater?

A 40-gallon electric water heater needs the proper wire size to operate safely and effectively. When choosing the wire size to utilize, you need to consider the voltage, amperage, and distance between the electrical panel and the heater.

The Water Heater’s Voltage

Usually, electric water heaters are powered by 120 or 240 volts. 40-gallon water heaters that run on 240 volts are the norm because of their great adaptability and high use volume.

The Water Heater’s Amp Rating

The dimensions and heating elements of the water heater determine its amperage rating. A 40-gallon electric water heater may get 30 amps from an electrical socket. Check the owner’s manual or the model’s label for the exact amperage rating of your water heater.

Wire Gauge

The NEC establishes recommended wire sizes by considering wire length and current (amperage). The ampacity, or ability to conduct current, plus the maximum voltage drop allowed to determine its size. The typical voltage loss threshold for domestic water heaters is 3 percent. Amplitude tables for different wire diameters and situations are available from the NEC. These requirements include the type of insulation and the highest temperature at which conductors can be used. To guarantee a safe and effective water heater installation, check the NEC tables to see whether wire size satisfies or surpasses the necessary ampacity.

Length of Electrical Panel

The distance between the water heater and the home’s electrical panel may impact the voltage drop of the heater. Larger wire diameters are typically required for longer wires to reduce voltage drop and guarantee correct heater performance.

10 2 or 10 3 Water Heater Wire

A 10/3 wire might be used for this. It is recommended to use the red and black wires as hot connectors. The green screw will be used to secure the grounding wire. Take the cover off the white wire. It will be impossible for your electrician to obtain the 10/3 wire your heater requires. If you already have one, though, they can fix it.

When wiring water heaters, electricians typically use this cable. There are two wires or conductors in a 10-2 cable. Perfect for 30A circuit breakers.


By considering the amperage, voltage, wattage, and expected workload, you can choose the appropriate wire size for your electric water heater. Using the appropriate wire gauge, you can ensure your electric water heater is safe and functional. To guarantee a correct installation, local electrical codes, and the manufacturer’s instructions must always be followed. It is best to seek advice from a certified electrician if you are unsure about performing electrical tasks.


What size wire is needed for a water heater that uses 4500 watts?

A 4500-watt water heater would require wire that is 10 gauge AWG in size. A current of up to 30 amps can flow through this wire.

A 120-volt water heater consumes how many amps?

A 2000-watt water heater at 120 volts will draw 16.66 amps; 80 percent of a 20-amp circuit is only 16 amps. If your voltage falls below 110 volts, as it does in some areas, the amperage drawn could reach 18.18 amps.