How Many Amps Does a Water Heater & Tankless Water Heater Use

Most electric water heaters operate at 240V and draw around 4500W of electricity per hour. If you want to calculate how many amps a water heater uses, you must divide the wattage by voltage. Generally, an electric water heater draws around 18.8 amps. Some models of heat pump water heaters and gas water heaters operate at 120V and consume 1000 - 2000W of electricity. They typically draw around 8.3 - 16.6 amps of current.

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Key Takeaways

• The small water heaters (10-gallon and 20-gallon), heat pump water heaters, and gas water heaters consume around 1000W—2000W of electricity and draw 8.3 - 16.6 amps of current when operating at 120V.
• Most residential water heaters (30-gallon to 50-gallon) draw 12.5 - 22.9 amps with 240V and 3000-5500W heating elements.
• The average 40-gallon water tank needs a 30-amp breaker to operate.
• The capacity of a tankless water heater is determined by the gallon used per minute. Models with higher flow rates tend to use more electricity.

How Many Amps Does a Water Heater Use?

The standard electric water heater draws 18.8 amps and 4500W of electricity with a 240V outlet. On the other hand, a 1200-watt gas water uses fewer amps, around 10 amps with 120 volts. A tankless water heater needs 15 - 25 amps of current at a 120V circuit to charge the control board and electric pilot light. However, the exact amount of water heater amps will vary depending on the key elements, such as the heater type, fuel type, and capacity.

Definition of Amps, Volts, Watts, and Running Watts

Amps, watts, and volts are the three electrical units that can help you determine the appliance's energy or power consumption, including how it affects your electricity bills. These terms will also help you determine how many amps an electric water heater draws on startup and while running.

Amps: Amperage, or amps, is the unit of electric current that flows through the electricity circuit. The water heater amps typically vary between 8 - 25 amps of current, depending on its type and capacity.

Amps = Watts ÷ Volts

Volts: Voltage is the potential difference driving the electric current through the circuit. It is also known as the pressure that pushes the electrons. Water heaters usually operate at 120V or 240V, depending on their type and wattage.

Volts = Watts ÷ Amps

Watts: Wattage is the unit of power that represents the appliance's power consumption (in this case, a water heater). How many watts a water heater uses can easily be calculated by multiplying its volts and amps.

Watts = Volts × Amps

Running Wattage: Running wattage (also called rated wattage) is the continuous power the appliance consumes for the time it operates. It is either equal to or lower than the starting wattage of the appliance and can be calculated as follows:

Running Wattage = Running Amps × Volts  

How Many Amps Does a Tank & Tankless Water Heater Use?

With so many different types of water heaters available in the market, it might be hard to know how many amps a water heater uses. Without the right water heater amps, the electrical system can become overloaded. If you want to determine the water heater amps, you'll need to know its fuel type, capacity, and size. Here's a table revealing the watts, volts, and amps of different water heaters:

How Many Amps Does a Water Heater Draw on a Startup?

Unlike other appliances, such as air conditioners and refrigerators, water heaters do not require startup amps or wattage. In general, devices with motors often draw more power on startup. However, water heaters operate only at heating elements, which means their power consumption will remain consistent from the moment they are turned on.

Starting Watts vs Running Watts

Since water heaters do not have motors, they do not draw more power when they start. Instead, the startup wattage and running wattage are nearly identical. For example, if your water heater is rated for 4500 watts, it will draw close to that amount consistently when it starts. Once a water heater is on, it continuously draws the same wattage until the water reaches the desired temperature and the thermostat shuts off the heating element.

Startup Amps vs Running Amps

Like air conditioners, water heaters generally do not have a significant spike in starting amps. This is because they use resistive heating elements, which do not require an initial surge of power to start. When the water heater is turned on, it will draw the same amount of current until the water reaches the set temperature. For example, a small 1200W water heater operating at 120V will consume 10 amps of current when operating continuously.

Running Amps = Running Watts ÷ Volts = 1200W ÷ 120V = 10 amps

If we suppose there are some power fluctuations and the water heater consumes around 1300 watts at startup, the values of amps can be calculated as follows:

Startup Amps = Running Watts ÷ Volts = 1300W ÷ 120V = 10.8 amps

How to Calculate Your Water Heater Amps

Electric water heaters are essential appliances that can provide hot water for daily needs such as laundry, washing dishes, and showering. However, the daily power consumption of these water heaters can significantly contribute to the electricity bills. If you want to better calculate the amp usage of electric water heaters, here are the three methods to check out:

Method 1: Manufacturer Details — Energy Star Rating

One of the easiest and most accurate methods to determine the water heater amps is by checking the manufacturer's details. They are usually available on the front or back side of the water heater, on the user manual, or the manufacturer's website. You can determine the accurate amp usage based on the water heater model and type. If you have an Energy Star-rated water heater, you can check the Energy Star label to find out the amps and power consumption of the appliance.

Method 2: Determine the Amps from the Wattage

The formula for calculating the water heater amps from the wattage is pretty simple. If you have a large water heater drawing 4500W of electricity and operating at 240V, the amps can be calculated as follows:

Amps = Watts ÷ Volts = 4500W ÷ 240V = 18.8 amps

You can check the appliance wattage chart to determine the wattage of the water heater and then calculate the amps. If you use the 4500-watt water heater for one hour daily, your total power consumption will be 4500Wh per day.

Daily Amps = Watt-Hours ÷ Volts = 4500Wh ÷ 240V = 18.8Ah

Method 3: Use a Clamp Meter

The third way to determine how many amps a water heater uses is to install a clamp meter. It can safely measure the current without breaking the circuit. All you need to do is clamp the meter around one of the wires going to the heater and get an accurate reading of the amps.

Tips to Save Your Electricity Bill

Your water heater is one of the power-hungry appliances among the household appliances. If you want to reduce the electricity bills because of water heater, here are a few tips to check out:

Don't Stay Too Long in the Shower: While a hot shower can be relaxing, consider limiting the bathing time and avoiding 20-30-minute sessions. A good technique is to turn off the shower while you soap or wash the hair and then restore the water to rinse off.

Insulate the Tank: You can consider purchasing an inexpensive insulation blanket to help the water tank retain its heat so it expends less energy to warm all over again.

Find the Right Tank Size: You should consider a water heater large enough to handle your house's busiest hours. However, it shouldn't be too large that it wastes energy heating water you don't need. It's better to look for how many gallons you need in an hour and then choose a model.

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Solar Generators for Water Heaters

Jackery Solar Generators are reliable and eco-friendly generators that can charge most household appliances, including different sizes of off-grid water heaters, air conditioners, TVs, lights, coffee makers, etc. Jackery can power water heaters, but the choice of the right size solar generator will depend on the power consumption and type of water heater.

Solar generators typically combine portable solar panels and battery power stations to generate electricity from sunlight. You can unfold and place the solar panels under direct sunlight so they absorb the sunlight and generate DC electricity. The portable power station has a built-in pure sine wave inverter that converts the DC to AC electricity to charge various appliances for hours.

Jackery Solar Generator 2000 Plus

If you have a small water heater (10-gallon—20-gallon) operating at 120V installed at your home, you can consider the versatile Jackery Solar Generator 2000 Plus. It's ideal for people who live in areas that face frequent blackouts or power outages. The battery capacity is also expandable, so you can extend it to 24kWh to reduce your monthly electricity bills.

Jackery Solar Generator 3000 Pro

The Jackery Solar Generator 3000 Pro is a large-capacity power solution that can charge 99% of indoor or outdoor appliances for hours. Its portable design with double wheels and pull rods ensures easy movement from one place to another. It's ideal for water heaters that work on a 120V outlet, allowing you to have hot water during unexpected power outages, off-grid living, or blackouts.

Jackery Explorer 2000 Plus Double Kit

The Jackery Explorer 2000 Plus Double Kit is a battery-powered generator that can charge electric water heaters operating at 240V. It's built by connecting two Jackery Explorer 2000 Plus Portable Power Stations in parallel to increase the voltage and wattage. It can safely charge different sizes and types of electric water heaters during off-grid living, blackouts, and power outages.

FAQs About Water Heater Amps

How many amps does a 50-gallon water heater use?

When operating at 240 volts, a 50-gallon water heater typically consumes 5000 watts and 20.8 amps. However, the actual water heater amps can vary depending on the specific model and its wattage consumption.

How many amps does a 40-gallon water heater use?

A 40-gallon water heater consumes 4000W, operates at 240V, and draws around 16.6 amps. However, you should check the label on the water heater to know the exact watts, volts, and amps consumption.

How many amps does a 240-volt water heater use?

A 240-volt electric water heater with a 4500-watt heating element typically uses 18.8 amps. However, the exact amount of amps a water heater uses depends on its tank capacity and other factors.

Conclusion 

Most residential water heaters consume 1000W - 4500W of electricity per hour. However, the operating voltage and how many amps a water heater uses depends on the size and type of the appliance. For example, water heaters operating at 120V will draw 8.3 - 16.6 amps of current. Larger water heaters consume as much as 20 - 30 amps of current. Jackery Solar Generators are ideal solutions that charge up to 99% of household appliances, such as water heaters. They can help you reduce the reliance on the electricity grid and switch to a more sustainable lifestyle.